ARTICLE | doi:10.20944/preprints202009.0763.v1
Subject: Chemistry, Analytical Chemistry Keywords: ab initio; sulphur dioxide; ozone; dimers; complexes; structures; vibrational spectra.
Online: 30 September 2020 (18:36:52 CEST)
The structures of a number of dimers of sulphur dioxide and ozone have been optimized by means of a series of ab initio calculations. The dimer species have been classified as either genuine energy minima or transition states of first or higher order, and the most probable structures consistent with the experimental data have been confirmed. The molecular orbitals engaged in the interactions resulting in adduct formation have been identified and relations between the orbitals of the dimers of the valence isoelectronic monomer species examined. The vibrational spectra of the most probable structures have been computed, and compared with those reported in the literature, particularly with spectra observed in cryogenic matrices. The calculations have been extended to predict the properties of a number of possible heterodimers formed between sulphur dioxide and ozone.
ARTICLE | doi:10.20944/preprints202009.0762.v1
Subject: Chemistry, Analytical Chemistry Keywords: Bentonite; Phosphogypsum; Slag; Lime; Hydration; Kinetics; Pozzolanic reactions.
Online: 30 September 2020 (18:01:21 CEST)
The Black Steel slag (Ss) and phosphogypsum (PG) are industrial wastes produced in Morocco. In order to reduce these two wastes and to evaluate their pozzolanic reactivity in the presence of water, they were incorporated into bentonite (B) mixed with lime (L). The studied mixtures (BLW, BL-PG-W and BL-PG-Ss-W) were analyzed by X-ray diffraction, Infrared spectroscopy, Raman spectroscopy and SEM/EDX analysis. Compressive strength tests were performed on hardened specimens. The results obtained show that the hydration kinetics of the B-L-W and B-L-PG-W mixtures are slow. The addition of PG to a bentonite-lime mixture induces the formation of new microstructures such as hydrated calcium silicate (C-S-H) and ettringite, which increases the compressive strength of the cementitious specimens. The addition of the Ss to a mixture composed by 8%PG and 8%L-B accelerates the kinetics of hydration and activates the pozzolanic reaction. The presence of C2S in the slag helps to increase the mechanical strength of the mixture B-L-PG-Ss. The compressive strength of the mixtures BL-W, BL-PG-W and BL-PG-Ss-W increases from 15 to 28 days of setting. After 28 days of setting, 8% of Sc added to the mixture 8% PG-8%L-B is responsible for an increase of the compressive strength to 0.6 MPa.
Subject: Chemistry, Analytical Chemistry Keywords: multiscale computation; electron transfer; light harvesting
Online: 30 September 2020 (16:44:21 CEST)
A tremendous effort is currently devoted to the generation of novel hybrid materials with enhanced electronic properties for the creation of artificial photosynthetic systems. This compelling and challenging problem is well-defined from an experimental point of view, as the design of such materials relies on combining organic materials or metals with biological systems like redox-active proteins. Such hybrid systems can be used e.g. as bio-sensors, bio-fuel cells, biohybrid photoelectrochemical cells and nanosctuctured photoelectronic devices. Despite these efforts, the main bottleneck is the formation of efficient interfaces between the biological and the organic/metal counterparts for efficient electron transfer (ET). It is within this aspect that computation can make the difference and improve the current understanding of the mechanisms underneath the interface formation and the charge transfer efficiency. Yet, the systems considered are more and more complex, reaching (and often passing) the limit of current computation power. In this review, recent developments in computational methods for studying complex systems for artificial photosynthesis will be provided and selected cases discussed, to assess the inherent ability of computation to leave a mark in this field of research.
ARTICLE | doi:10.20944/preprints202009.0731.v1
Subject: Chemistry, Analytical Chemistry Keywords: Cosmetic, Heavy metals, Toxicity, Cadmium, Atomic Absorption Spectroscopy.
Online: 30 September 2020 (09:07:14 CEST)
Throughout the ages and times, the need to use everything that reflects women's beauty and helps them maintain their vision and health, and if the need to use the precious materials has been put in place, it is important that they produce the desired results without attention to the harmful chemicals and heavy metals that they contain. Over time, the toxicity of these heavy metals increases in our environment because of their long-term exposure to these pollutants, whether low or high-level in toxicity, animal-prednmost, environment, including air we breathe, water, food, etc. Cosmetics are one of these sources through which humans are exposed to heavy toxic metals. Heavy metals have been estimated in a number of previous studies, and in our study here, we aim to estimate the amount of cadmium metal and study it in various cosmetics such as Lipstick, Eye shadow, Face whitening cream. Two samples were taken from each of the locomoys and cadmium was estimated using the photometer of atomic absorption, one of the samples being expensive and the other low-cost, and purchased from the wholesale markets of Taiz City. Cadmium has been found prominently in these products and the highest rate found in the lowest cost-effective, Eye shadow, that the use of these cosmetic products exposes users to low- conc. heavy metals, which may pose a danger to their health. They are known to be clustered in their biological systems over time, resulting in an imbalance of body and environment. The results found that the low-priced color samples contained a higher concentration of cadmium than the high-price samples in low-priced samples, cadmium concentration was in order of eye shadow > lipstick = face whitening cream. The similar pattern are shown also for higher price product, which are lipstick > face whitening cream > eye shadow.
Tue, 29 September 2020
ARTICLE | doi:10.20944/preprints202009.0703.v1
Subject: Chemistry, Analytical Chemistry Keywords: açaí; total polyphenol; total anthocyanin; antioxidant; elemental analysis; essential elements; biological activity; wound healing
Online: 29 September 2020 (09:14:48 CEST)
Chemical composition analysis of açaí extracts revealed higher levels of total polyphenol content in purple açaí samples for both commercial (4.3 – 44.7 gallic acid equivalents mg/g) and non-commercial samples (30.2 – 42.0 mg/g) compared to white (8.2 – 11.9 mg/g) and oil samples (0.8 – 4.6 mg/g). The major anthocyanin compounds found in purple açaí samples were cyanidin-3-glucoside and cyanidin-3-rutinoside with total concentrations in the range of 3.6 – 14.3 cyanidin-3-glucoside equivalents mg/g. The oligomeric proanthocyanidins were quantified in the range of 1.5 – 6.1 procyanidin B1 equivalents mg/g. Moreover, açaí presented significant levels of calcium, magnesium, manganese, iron, zinc and copper, essential minor and trace elements, in comparison with other berries. All of the açaí extracts at 50 μg/mL potently inhibited the release of reactive oxygen species in lipopolysaccharide-stimulated RAW 264.7 macrophage cells, but none inhibited the release of nitric oxide. Furthermore, all the açaí samples demonstrated potential as wound healing agents due to the high levels of migration activity in human fibroblast cells.
Mon, 28 September 2020
ARTICLE | doi:10.20944/preprints202009.0689.v1
Subject: Chemistry, Analytical Chemistry Keywords: Molecular docking; α-Pyrone; antileukemic; CRM1inhibitors
Online: 28 September 2020 (15:35:00 CEST)
Some α-Pyrone derivatives isolated from Alternaria phragmospora fungus showed promising anti leukemic activities, while others were inactive. CRM1/XPO1 (chromosome region maintenance 1 protein, also called exportin1 or PO1 in humans) has been chosen as a target for antileukemic molecular docking study for those compounds to understand their modes of interaction and structure activity relationships. The results showed that two (2 and 4), out of six, natural α-Pyrone derivatives exhibited well-established interactions with the amino acids of the receptor, which was in agreement with the experimental anti-leukemic results of these compounds. Moreover, twenty hypothetical chemically modified α-Pyrone derivatives (7-27) have been designed. Compounds 7, 8, 22 and 24 showed more efficient docking properties than the previously considered natural compounds.
TECHNICAL NOTE | doi:10.20944/preprints202009.0683.v1
Subject: Chemistry, Analytical Chemistry Keywords: DNA extraction; normal; patients; protocol; frozen blood
Online: 28 September 2020 (10:52:59 CEST)
Herein, we describe a highly efficient, non-complicated, and non-organic procedure to overcome the negative effect of chemotherapeutic drugs on the quality of the extracted DNA by applying several modulations in cell washing, suspension, and lysis of cells treated with these drugs. In this protocol, 500µl were extracted from patients who received systemic sessions of chemotherapy. The validity of this protocol for digestion with restriction endonucleases and both conventional and real-time polymerase chain reaction were tested. This protocol proved obvious purity (1.8±0.02 and 2.1±1.2, for A260/280 and A260/230, respectively) and adequate yields (10±2.24) µg/100 ml. The positive results of validation experiments proved the validity of the extracted DNA for downstream applications of molecular biology. In addition to the proven efficiency of this protocol to extract DNA from normal samples, its validity was also confirmed from patients who were exposed to chemotherapy. This entails a novel approach to extract a molecular biology grade DNA without having inhibitors against enzymes used in digestion, amplification, and subsequent sequencing even after the systemic sessions with several doses of chemotherapy.
Sun, 27 September 2020
ARTICLE | doi:10.20944/preprints202009.0668.v1
Subject: Chemistry, Analytical Chemistry Keywords: magnetic solid-phase extraction; CoFe2O3 Nanoparticles; polyphenol; Lawsone; high-performance liquid chromatography
Online: 27 September 2020 (08:01:06 CEST)
A novel polyphenol‑coated CoFe2O4 system was synthesized as a magnetic adsorbent by chemical oxidative polymerization process for magnetic solid-phase extraction of lawsone. The synthesized nanoadsorbent showed a spherical morphology with diameters under 50 nm by scanning electron microscopy images. The extraction efficiency of this adsorbent was studied towards the extraction of lawsone from saline aqueous solution in dispersion mode. Major parameters including the type and volume of desorption solvent, amount of sorbent, desorption time, extraction time, extraction temperature, ionic strength and pH were optimized. Under the optimum conditions the relative standard deviation in 0.005 µg mL-1 (inter-day n = 6; intra-day: n = 6; and adsorbent to adsorbent n = 4) were obtained as 5.2, 8.07 and 11.7%, respectively. A linear calibration curve in the range of 0.003–0.5 µg mL-1 with R2 = 0.993 was obtained. The limit of detection and limit of quantification of the method were 0.001 µg mL-1 and 0.003 µg mL-1, respectively. The relative recovery percentages were in range of 90-96.4% for henna leaves, henna shampoo, and henna dermal lotion real samples.
ARTICLE | doi:10.20944/preprints202009.0660.v1
Subject: Chemistry, Analytical Chemistry Keywords: metformin cocrystal; mechanochemical synthesis; dicationic metformin; water channels; pi-interactions; mesoporous anhydrate
Online: 27 September 2020 (04:12:17 CEST)
A new cocrystal salt of metformin, an antidiabetic drug, and N,N’-(1,4-phenylene)dioxalamic acid, was synthesized by mechanochemical synthesis, purified by crystallization from solution and characterized by single X-ray crystallography. The structure revealed a salt-type cocrystal composed of one dicationic metformin unit, two monoanionic units of the acid and four water molecules namely H2Mf(HpOXA)2∙4H2O. X-ray powder, IR, 13C-CPMAS, thermal and BET adsorption-desorption analyses were performed to elucidate the structure of the molecular and supramolecurar structure of the anhydrous microcrystalline mesoporous solid H2Mf(HpOXA)2. The results suggest that their structures, conformation and hydrogen bonding schemes are very similar between them. To the best of our knowledge, the selective formation of the monoanion HpOXA⁻, as well as its structure in the solid, is herein reported for the first time. Regular O(-)∙∙∙C(), O(-)∙∙∙N+ and bifacial O(-)∙∙∙C()∙∙∙O(-) of n→* charge-assisted interactions are herein described in H2MfA cocrystal salts which could be responsible of the interactions of metformin in biologic systems. The results, support the participation of n→* charge-assisted interactions independently, and not just as a short contact imposed by the geometric constraint due to the hydrogen bonding patterns.
Sat, 26 September 2020
Subject: Chemistry, Analytical Chemistry Keywords: NMR spectroscopy; honey; honeydew honey; geographical origin; classification
Online: 26 September 2020 (16:58:24 CEST)
Bulgaria and North Macedonia have a long history of production and use of honey, however, there is an obvious lack of systematic and in-depth research on honey from both countries. Of particular interest is the oak honeydew honey, highly valued by consumers because of its health benefits. Aim of this study was to characterize honeydew and floral honeys from Bulgaria and North Macedonia based on their NMR profiles. 1D and 2D 1H and 13C NMR spectra were measured of 16 North Macedonian and 22 Bulgarian honey samples. 25 individual substances were identified, including quinovose, which was found for the first time in honey. Chemometric methods (PCA - principal component analysis, PLS-DA - partial least squares discriminant analysis, ANOVA) were used to detect similarities and differences between samples, as well as to determine their botanical and geographical origin. Semiquantitative data on individual sugars and some other constituents were obtained; which allowed reliable classification of honey samples by botanical and geographical origin, based on chemometric approaches. The results enabled to distinguish oak honeydew honey from other honey types, and to determine the country of origin. NMR was a rapid and convenient method, avoiding the need for other more time-consuming analytical techniques.
ARTICLE | doi:10.20944/preprints202009.0643.v1
Subject: Chemistry, Analytical Chemistry Keywords: dispersion; ketone-alcohol complexes; density functional theory; hydrogen bonds; molecular recognition; vibrational spectroscopy; gas phase; benchmark; pinacolone
Online: 26 September 2020 (14:57:33 CEST)
The influence of distant London dispersion forces on the docking preference of alcohols of different size between the two lone electron pairs of the carbonyl group in pinacolone is explored by infrared spectroscopy of the OH stretching fundamental in supersonic jet expansions of 1:1 solvate complexes. Experimentally, no pronounced tendency of the alcohol to switch from the methyl to the bulkier tert-butyl side with increasing size is found. In all cases, methyl docking dominates by at least a factor of two, whereas DFT-optimized structures suggest a very close balance for the larger alcohols, once corrected by CCSD(T) relative electronic energies. Together with inconsistencies when switching from a C4 to a C5 alcohol, this points at deficiencies of the investigated B3LYP and in particular TPSS functionals even after dispersion correction, which cannot be blamed on zero point energy effects. The search for density functionals which describe the harmonic frequency shift, the structural change and the energy difference between the docking isomers of larger alcohols to unsymmetric ketones in a satisfactory way is open.
Fri, 25 September 2020
ARTICLE | doi:10.20944/preprints202009.0607.v1
Subject: Chemistry, Analytical Chemistry Keywords: Milk Serum; whey proteins; RP-HPLC-UV; free amino acids; RP-HPLC-FLD; antimicrobial study
Online: 25 September 2020 (11:45:09 CEST)
The aim of this study was characterization of some dairy drinks based on Milk Serum regarding major whey proteins (WP) and free amino acids (FAAs) using reversed phase high performance liquid chromatographic (RP-HPLC) methods. The studied WP, -lactalbumin (-La), bovine serum albumin (BSA), -lactoglobulin A (-Lg A) and -lactoglobulin B (-Lg B) were separated on Aeris XB-C18 column at 214 nm detection. The RP-HPLC method was validated by selectivity, linearity (R2 ≥0.99), sensitivity (LOQ, 1.35–10.08 µg mL−1), accuracy (recovery 96.79-103.07%) and precision (% RSD ≤ 4.13%). The total studied WP in studied dairy drinks varied between 1.42 and 3.047 g·L-1. The chromatographic profile of FAAs (aspartic acid, glutamic acid, serine, histidine, arginine, glycine, threonine, alanine, tyrosine, cysteine, tryptophan, methionine, valine, phenylalanine, isoleucine, leucine and lysine) was determined in lyophilized concentrate of Milk Serum by RP-HPLC using pre-column derivatization reaction with orthophthalaldehyde (OPA). The total studied FAAs in studied samples varied between 1.103 and 1.119 mg·g-1. Moreover, the Milk Serum showed bacteriostatic activity against two bacterial strains Escherichia coli and Staphylococcus aureus. The obtained results confirm that dairy drinks based on the Milk Serum constitutes a valuable sources of bioactive components with benefits for human healthy nutrition.
Wed, 23 September 2020
ARTICLE | doi:10.20944/preprints202009.0536.v1
Subject: Chemistry, Physical Chemistry Keywords: 3,3’,5,5’-tetramethylbenzidine; reactive oxygen species (ROS); reactive nitrogen species (RNS); photoacoustic probes; optical sensors; singlet oxygen
Online: 23 September 2020 (04:17:34 CEST)
Photoacoustic imaging is attracting a great deal of interest owing to its distinct advantages over other imaging techniques such as fluorescence or magnetic resonance image. Availability of photoacoustic probes for reactive oxygen and nitrogen species (ROS/RNS) could shed light on a plethora of biological processes mediated by these key intermediates. Tetramethylbenzidine (TMB) is a non-toxic and non-mutagenic colorless dye that develops a distinctive blue color upon oxidation. In this work we have investigated the potential of TMB as photoacoustic probe for ROS/RNS. Our results indicate that TMB reacts with hypochlorite, hydrogen peroxide, singlet oxygen and nitrogen dioxide to produce the blue oxidation product, while ROS such as the superoxide radical anion, sodium peroxide, hydroxyl radical or peroxynitrite yield a colorless oxidation product. TMB does not penetrate Escherichia coli cytoplasm but is capable of detecting singlet oxygen generated in its outer membrane.
Tue, 22 September 2020
ARTICLE | doi:10.20944/preprints202009.0523.v1
Subject: Chemistry, Analytical Chemistry Keywords: Anticancer; Tubulin; HSP27; Nimesulide; SKOV3; SKBR3
Online: 22 September 2020 (15:19:02 CEST)
Tubulin and heat shock protein 27 (HSP27) are up-regulated in cancer cells, and play a critical role in cell division, and proliferation. Therefore, they are targets for discovery of anticancer therapy. The objective of this study is to design, characterize, and biologically evaluate the nimesulide analogues to combat female cancer such as ovarian cancer, and breast cancer. Herein, the nimesulide analogues are designed to target both tubulin and HSP27 functions. Ovarian cancer (SKOV3) and breast cancer (SKBR3) cell lines were used as surrogate models to test the nimesulide analogs biological activities using MTT assay. In the present study, four nimesulide analogues were designed, synthesized and the chemical structures were with the biological evaluation were studied. The synthesized agents were characterized by 1H-NMR, 13C-NMR, the molecular weight was confirmed using GC-MS technique, and melting point. Besides, the agent L4 structure was confirmed using X-ray crystallographic analysis. The present data revealed that nimesulide analogs have potent anticancer activity against SKOV3and SKBR3 cell lines. The IC50 values for both SKOV3 and SKBR3 cell lines treated with the agents showed a potent cell growth inhibition range of 0.23-2.02 µM and 0.50-3.73 µM respectively. In conclusion, the designed nimesulide analogues can target both tubulins, and HSP27 concurrently, and they are promising agents as future chemotherapy female cancers.
Mon, 21 September 2020
ARTICLE | doi:10.20944/preprints202009.0504.v1
Subject: Chemistry, Applied Chemistry Keywords: Water-soluble MoS2 quantum dots; , Fluorescent probe; Fe3+ ion sensor; Living cells
Online: 21 September 2020 (14:49:23 CEST)
Uniform water soluble MoS2 quantum dots (WS-MSQDs) are synthesized via a sequential combination of sintering/etching/exfoliation method and solvothermal route. The obtained WS-MSQDs with average size of approximately 3.4 nm exhibit sufficient water solubility and remarkable fluorescence properties. The WS-MSQDs have been utilized as a probe for detection of Fe3+ ions with high selectivity and specificity. Furthermore, the WS-MSQDs exhibit high fluorescence stability under different conditions. Finally, the WS-MSQDs are successfully applied for the fluorescence imaging of Fe3+ in living cells, which exhibited practical potential for biomedical applications.
Thu, 17 September 2020
ARTICLE | doi:10.20944/preprints202009.0391.v1
Subject: Chemistry, Medicinal Chemistry Keywords: Diabetes mellitus; oxidative stress; alpha-glucosidase; alpha-amylase; Salvia aurita; abietane diterpenes
Online: 17 September 2020 (09:03:16 CEST)
Diabetes mellitus (DM) is one of the most dangerous metabolic diseases with high rate of mortality worldwide. It is well known that insulin resistance and deficiency in insulin production from pancreatic β-cells are the main characteristic of DM. Due to the detrimental side effects of the current treatment, there is a considerable need to develop new effective antidiabetic drugs, especially alpha-glucosidase and alpha-amylase inhibitors with lesser adverse effects. These inhibitors are known to be directly involved in the delay of carbohydrate digestion, resulting in a reduction of glucose absorption rate and consequently reduce the post-prandial raise of plasma glucose, which can reduce the risk of long-term diabetes complications. Hence, natural products are well-known sources for the discovery of new scaffold for drugs discovery, including new antidiabetic drugs. The phytochemical investigation of Salvia aurita collected from Hogobach pass, Eastern Cape, South Africa (SA), yielded four known abietane diterpenes namely carnosol (1), rosmanol (2), 7-methoxyrosmanol (3), 12-methoxycarnosic acid (4) and one flavonoid named 4,7-dimethylapigenin (5). Structural characterization of these isolated compounds was conducted using 1 and 2D NMR, in comparison with reported spectroscopic data. These compounds are reported for the first time from S. aurita. The biological evaluation of the isolated compound against alpha-glucosidase exhibited strong inhibitory activities for 3 and 2 with IC50 values of 4.2 ± 0.7 and 16.4 ± 1.1 µg/mL respectively, while 4 and 1 demonstrated strong alpha-amylase inhibitory activity amongst the isolated compounds with IC50 of 16.2 ± 0.3 and 19.8 ± 1.4 µg/mL. Molecular docking analysis confirms strong inhibitory activity of 3 against alpha-glucosidase. Additionally, excellent antioxidant capacities were displayed by 2, 1 and 3 respectively as ORAC (25789.9 ± 10.5; 23961.8 ± 14.1; 23939.3 ± 2.4) µM TE/g; 1 and 2 as FRAP (3917.8 ± 2.1; 1522.3 ± 0.9) µM AAE/g; 5 and 2 as TEAC (3190.4 ± 2.8; 2055.0 ± 2.6) µM TE/g. The methanolic extract of S. aurita is a rich source of abietane diterpenes with excellent antioxidant and anti-diabetic activities that can be useful to modulate oxidative stress, and might possibly be excellent candidates for the management of diabetes. This is the first scientific report on the phytochemical isolation and biological evaluation of alpha-glucosidase and alpha-amylase inhibitory activities of Salvia aurita.
Mon, 14 September 2020
ARTICLE | doi:10.20944/preprints202009.0300.v1
Subject: Chemistry, Physical Chemistry Keywords: DNA Nucleotides; Transcription; Structural Symmetry
Online: 14 September 2020 (04:39:55 CEST)
To activate gene expression, the initiation of transcription is a highly regulated process involving the interaction of proteins and DNA nucleotides at the promoter site, which consists of a small number of base pairs. As it involves interactions at the atomic scale, it is challenging to determine the mechanism of binding responsible for the great specificity between the amino acid residuals comprising the transcription binding protein and the DNA nucleotides comprising the promoter. Here, a new approach to characterize the transcription initiation process is developed and verified from analysis of comparative pharmacological efficacy data and elemental modeling. The newly developed description of a mechanism for transcription initiation involves the direct binding of small molecule ligands of approximately twenty carbon atoms, which are both structurally symmetric to DNA nucleotides, and also chemically complementary in its functional groups for interaction with the oxygen element at the carbon two position of thymine and with the phosphodiester chain. The results indicate that the activating ligands are transported to the DNA nucleotide promoter site by protein transcription factors, which serve as delivery vectors, for transfer of the ligand to the DNA nucleotide pairs. The ligands examined in this study include the steroid hormones, synthetic steroid molecules, derivatives of vitamin D, and prostaglandins, particularly PGJ2 and 15d-PGJ2. The transcription factors evaluated include glucocorticoid receptors, VDR, PPAR, and TBP. Through the developments, it is shown that because of the chemically complementary binding of the ligand to DNA nucleotide pairs, the resultant intermolecular complex produces three hydrogen bonds for the A-T and T-A configurations, which matches that of G-C and C-G. The orientation of the nucleotide base pairs is also seen to adjust as an inversion of the nominal position of the nucleobases to a dimer configuration presented via TBP transcription factor. The developments comprise a new approach to characterizing the initiation of the transcription process comprising the direct binding and interaction of ligands with DNA nucleotides as verified through comparative analysis of pharmacological activity and through perfect structural correspondence between the steroid hormone class as ligands with Watson-Crick DNA nucleotide pairings.
ARTICLE | doi:10.20944/preprints202009.0317.v1
Subject: Chemistry, Food Chemistry Keywords: ICP-MS; trace elements; wine; Nizza; Barbera; authentication
Online: 14 September 2020 (00:49:48 CEST)
Barbera d'Asti - including Barbera d'Asti superiore - and Nizza are two DOCG (Denominazione di Origine Controllata e Garantita) wines produced in Piemonte (Italy) from Barbera grape variety. Differences among them arise in the production specifications in terms of purity, ageing and zone of production, in particular with concern to Nizza, which has more stringent rules and can therefore be considered as the one with the highest market value, with even three-fold more average prices. To guarantee producers and consumers, authentication methods must be developed in order to distinguish among the different wines. As the production zones totally overlap, it is important to verify whether the distinction is possible or not according to metals content, or whether chemical markers more linked to winemaking are needed. In this work, Inductively Coupled Plasma (ICP) elemental analysis and multivariate data analysis are used to study the authentication and traceability of samples from the three designations of 2015 vintage. The results show that, as far as elemental distribution in wine is concerned, work in the cellar, rather than geographic provenance, is crucial for the possibility of distinction.
Fri, 11 September 2020
REVIEW | doi:10.20944/preprints202009.0256.v1
Subject: Chemistry, Physical Chemistry Keywords: attractive and repulsive forces; Debye’s screening length (1/k); Poisson-Boltzmann (PB) equation; food colloids; coagulation; stabilizers; lipids; polymers; electrolytes
Online: 11 September 2020 (10:05:50 CEST)
Different forces play a key-role in the stability of food colloid dispersions. Focus is here on those controlling attraction and/or repulsion, which concur to stabilization, phase separation, coagulation, and are quite evident in water-based systems. Combination of attractive and repulsive forces favors, or hinders, the association of colloid entities; such processes are often met in food technology. The above processes depend on the forces at work, and on colloid concentration in the medium (i.e. on inter-particle distance). Worked examples deals with milk manipulation procedures, ending in cheese formation. The whole milk-working sequence is controlled by the combination of forces leading to aggregation and phase separation of casein and other milk components. Thereafter, one gets either fresh, for prompt consumption, or aged cheeses. The combination of attractive (van der Waals, vdW, and depletion) with repulsive (double layer, DL, but also with steric) forces results in the dominance of aggregation versus dispersion modes in all steps of milk transformation, which depend on the distance among colloid particles, on the amplitude of the mentioned forces, and on their decay length. The combined role of double layer and van der Waals (vdW) forces is at the basis of the DLVO theory on colloid stability, which is properly modified when these forces overlap with steric stabilization and, eventually, with depletion. Steric effects are dispersive, depletion ones favor colloid nucleation in a single phase. The milk manipulation chain is a worked example of the intriguing association features controlled by the mentioned forces (and of ancillary ones, as well), and indicates which forces favor the formation of products such as Parmesan or Mozzarella cheese, but are not alien to the preparation of many other dairy products.
ARTICLE | doi:10.20944/preprints202009.0255.v1
Subject: Chemistry, Food Chemistry Keywords: antioxidant enzymes; hydrogen peroxide; phenylalanine ammonia-lyase; proline; scanning electron microscopy
Online: 11 September 2020 (09:58:41 CEST)
Susceptibility of four blood orange cultivars (‘Moro’, ‘Tarocco’, ‘Sanguinello’ and ‘Sanguine’) to chilling injury (CI) was studied. Antioxidant enzymes, physiological and biochemical changes were measured monthly at 2 and 5 °C plus 2 days at 20 °C for shelf life. At 2 °C, CI symptoms were higher than at 5 °C, and ‘Moro’ and ‘Tarocco’ had significantly higher CI than ‘Sanguinello’ and ‘Sanguine’. ‘Moro’ and ‘Tarocco’ had the highest electrolyte leakage, malondialdehyde, H2O2 and polyphenol oxidase activity and lower phenylalanine ammonia-lyase compared with ‘Sanguinello’ and ‘Sanguine’. The scanning electron microscopy micrographs revealed that ‘Moro’ and ‘Taroco’ showed severe fractures in the flavedo due to CI. ‘Sanguinello’ and ‘Sanguine’ were more tolerant to CI due to an increase of catalase, ascorbate peroxidase and superoxide dismutase, which could prevent the loss of membrane integrity and alleviate CI symptoms. The order of susceptibility of cultivars to CI was ‘Moro’> ‘Tarocco’> ‘Sanguine’> ‘Sanguinello’.
Thu, 10 September 2020
ARTICLE | doi:10.20944/preprints202009.0232.v1
Subject: Chemistry, Applied Chemistry Keywords: limocitrol; lemon; citrus; bioeconomy; biocolorant; flavonoids
Online: 10 September 2020 (09:12:44 CEST)
A brief technical and economic insight into producing the water-soluble yellow colorant limocitrol 3-O-6”-[3-hydroxyl-3-methylglutaryl)])-β-D-glucopyranoside from waste lemon peel via simple solid-liquid extraction in aqueous ethanol or via hydrodynamic cavitation of waste lemon peel in water, shows that the biocolorant can be obtained at affordable cost. Coupled to the simplicity and sustainability of the extraction processes suggested, the high chemical and physical stability of this polymethoxylated flavanol and the health benefits of citrus flavonoids, support industrialization of this new bioeconomy production.
ARTICLE | doi:10.20944/preprints202009.0231.v1
Subject: Chemistry, Food Chemistry Keywords: organic acids; sugars; anthocyanins; antioxidant enzymes; ascorbic acid
Online: 10 September 2020 (09:11:16 CEST)
The changes in nutritional quality, bioactive compounds and antioxidant enzymes in the juice of four blood orange cultivars (‘Moro’, ‘Tarocco’, ‘Sanguinello’ and ‘Sanguine’) stored during 6 months at 2 and 5 °C plus 2 days at 20 °C for shelf life were studied. Sucrose was the sugar found at higher concentration and decreased during storage for all cultivars, as did glucose and fructose. Organic acids decreased at both temperatures and the highest content was found in ‘Sanguinello’, especially the major (citric acid) and ascorbic acid. Total phenolics content (TPC), total anthocyanins (TAC), and the individual (cyanidin 3-glucoside and cyanidin 3-(6″-malonylglucoside)) increased for all cultivars, the ‘Sanguinello’ having the higher concentrations. Antioxidant enzymes catalase (CAT), ascorbate peroxidase (APX) and superoxide dismutase (SOD) were higher also in ‘Sanguinello’ and increased during storage. Overall, these results together with the sensory analysis suggest that ‘Sanguinello’ would be the best cultivar for prolonged storage.
Tue, 8 September 2020
Subject: Chemistry, Analytical Chemistry Keywords: glycolipidomics; GIPC; glycosyl inositol phospho ceramides; Lipid Data Analyzer; lipidomics; sphingolipids; ultra-high pressure liquid chromatography; high-resolution mass spectrometry; LC-MS; automated annotation
Online: 8 September 2020 (12:34:56 CEST)
Glycosyl inositol phospho ceramides (GIPCs) are the major sphingolipids on earth as they account for a considerable fraction of the total lipids in plants and fungi which in turn represent a large portion of the biomass on earth. Despite their obvious importance, GIPC analysis remains challenging due to the lack of commercial standards and automated annotation software. In this work, we introduce a novel GIPC glycolipidomics workflow based on reversed-phase ultra-high pressure liquid chromatography coupled to high-resolution mass spectrometry. For the first time, automated GIPC assignment was performed using the open-source software Lipid Data Analyzer based on platform-independent decision rules. Four different plant samples (salad, spinach, raspberry, strawberry) were analyzed and revealed 64 GIPCs based on accurate mass, characteristic MS2 fragments and matching retention times. Relative quantification using lactosyl ceramide for internal standardization revealed GIPC t18:1/h24:0 as the most abundant species in all plants. Depending on the plant sample, GIPCs contained mainly amine, N-acetylamine or hydroxyl residues. Most GIPCs revealed a Hex-HexA-IPC core and contained a ceramide part with a trihydroxylated t18:0 or t18:1 long chain base and hydroxylated fatty acid chains ranging from 16 to 26 carbon atoms in length (h16:0 – h26:0). Interestingly, six GIPCs containing t18:2 were observed in raspberry, which was not reported so far. The presented workflow supports the characterization of different plant samples by automatic GIPC assignment potentially leading to the identification of new GIPCs. For the first time, automated high‑throughput profiling of these complex glycolipids is possible by liquid chromatography-high-resolution mass spectrometry and subsequent automated glycolipid annotation based on decision rules.
Sun, 6 September 2020
ARTICLE | doi:10.20944/preprints202009.0147.v1
Subject: Chemistry, Organic Chemistry Keywords: non-polar [3+2] cycloaddition reactions; regioselectivity; molecular electron density theory; electronegativity
Online: 6 September 2020 (15:59:37 CEST)
The regioselectivity in non-polar [3+2] cycloaddition (32CA) reactions has been studied within the Molecular Electron Density Theory (MEDT) at the B3LYP/6-311G(d,p) level. To this end, the 32CA reactions of nine simplest three-atom-components (TACs) with 2-methylpropane were selected. The electronic structure of the reagents has been characterised through the Electron Localisation Function (ELF) and the Conceptual DFT. The energy profiles of the two regioisomeric reaction paths and ELF of the transition state structures are studied to understand the origin of the regioselectivity in these 32CA reactions. This MEDT study permits to conclude that the least electronegative ends X1 atom of these TACs controls the asynchronicity in the C-X (X = C,N,O) single bond formation, and consequently, the regioselectivity. This behaviour is a consequence of the fact that the creation of the non-bonding electron density required for the formation of the new CX single bonds has a lesser energetic cost at the least electronegative X1 atom than that at the Z3 one.
Fri, 4 September 2020
ARTICLE | doi:10.20944/preprints202009.0077.v1
Subject: Chemistry, Electrochemistry Keywords: ionic imprinted polypyrrole; zinc oxide nanorods; mercury ions; diazonium salts; electrochemical sensor
Online: 4 September 2020 (03:28:26 CEST)
A biomimetic, ion-imprinted polymer (IIP) was prepared by electropolymerization of pyrrole at the surface of gold electrodes decorated with vertically grown ZnO nanorods. The vertical growth of the nanorods was achieved via an ultrathin aryl monolayer grafted by reduction of diazonium salt precursor. Pyrrole was polymerized in the presence of L-cysteine as chelatant agent and Hg(II) (template). Hg(II)-imprinted polypyrrole (PPy) was also prepared on bare gold electrode in order to compare the two methods of sensor design (Au-ZnO-IIP vs Au-IIP). Non-imprinted PPy was prepared in the same conditions, however in the absence of any Hg2+ template. The strategy combining diazonium salt modification and ZnO nanorod decoration of gold electrodes permitted to increase considerably the specific surface and thus to improve the sensor performances. The limit of detection (LOD) of the designed sensor was ~1 pM, the lowest value ever reported in literature. The dissociation constants between PPy and Hg2+ were estimated at [Kd1 = (7.89 ± 3.63) mM and Kd2 = (38.10 ± 9.22) pM]. The sensitivity of the designed sensor was found to be 0.692 ± 0.034 μA/pM. The Au-ZnO-IIP was found to be highly selective towards Hg(II) compared to cadmium, lead and copper ions. This sensor design strategy could open up new horizons in monitoring toxic heavy metal ions in water and therefore contribute to enhance environmental quality.
Thu, 3 September 2020
ARTICLE | doi:10.20944/preprints202009.0070.v1
Subject: Chemistry, Analytical Chemistry Keywords: inactivation column test; silanol; trace metals; in silico; bonded-phase silica
Online: 3 September 2020 (11:41:25 CEST)
The silanol activity and trace metal detection methods for chemically bonded silica gels were evaluated in silico. Test compounds with large molecular sizes may demonstrate negative results because of the possibility of indirect hydrogen bonding via short alkyl groups or siloxane of the silica gels. This hypothesis was based on the observation of weak hydrogen bonding energy values similar to those observed in the study of the alkyl group effect on the hydrogen bonding of alkanols. Consequently, smaller molecules may be a better choice for the analysis of bonded-phase quality.
ARTICLE | doi:10.20944/preprints202009.0057.v1
Subject: Chemistry, Applied Chemistry Keywords: Chromium; precipitation; tanning; leather industries; wastewater; sodium hydroxide
Online: 3 September 2020 (04:54:26 CEST)
Abstract The global concern about the leather industries is increasing as the leather industries grow bigger each year. These industries face a very challenging task with an increase in stringent pollution control regulation enforced by various bodies due to environmental concern and human risks. The chromium salts are the most widely used chemical for the tanning process in leather industries, about 35% of chromium used for the tanning process remain as metal and discharge to wastewater stream. The removal and recovery of this quantity of wasted chromium are necessary for environmental pollution control and economic reason. This paper sheds light on the chromium recovery and reuse system of Chromium salts in tanning wastewater by using NaOH as an effective chemical precipitation method to regenerate chromium solution, adapted chrome recovery plant, and evaluated the system technically and economically.
Wed, 2 September 2020
ARTICLE | doi:10.20944/preprints202007.0558.v2
Subject: Chemistry, Medicinal Chemistry Keywords: COVID-19; protein protein interactions; virtual screening; docking; molecular dynamics; zinc
Online: 2 September 2020 (09:48:48 CEST)
The outbreak of COVID-19, the disease caused by SARS-CoV-2, continues to affect millions of people around the world. The absence of a globally distributed effective treatment makes the exploration of new mechanisms of action a key step to address this situation. Stabilization of non-native Protein-Protein Interactions (PPIs) of the nucleocapsid protein of MERS-CoV has been reported as a valid strategy to inhibit viral replication. In this study, the applicability of this unexplored mechanism of action against SARS-CoV-2 is analyzed. During our research, we were able to find three inducible interfaces of SARS-CoV-2 N protein NTD, compare them to the previously reported MERS-CoV stabilized dimers, and identify those residues that are responsible for their formation. A drug discovery protocol implemented consisting of docking, molecular dynamics and MM-GBSA enabled us to find several compounds that might be able to exploit this mechanism of action. In addition, a common catechin skeleton was found among many of these molecules, which might be useful for further drug design. We consider that our findings could motivate future research in the fields of drug discovery and design towards the exploitation of this previously unexplored mechanism of action against COVID-19.
ARTICLE | doi:10.20944/preprints202009.0007.v1
Subject: Chemistry, Analytical Chemistry Keywords: Basic drugs; selective bonded-phase; in silico; solvent effect; electron localization
Online: 2 September 2020 (04:20:56 CEST)
Abstract: The quantitative analysis of the chromatographic behavior of basic compounds was performed in silico. The liquid chromatography (LC) data measured with pentyl-, hexenyl-, and octyl-bonded silica gels were analyzed in silico employing model phases. The main retention force was the van der Waals (VW) interaction, and the main desorption force was an electrostatic (ES) interaction. The contribution of hydrogen bonding (HB) was weak compared to that for acidic compounds. The quantitative explanation was achieved utilizing the calculated VW, HB, and ES energy values obtained from a molecular mechanics program. The electron localization was observed at the molecular interaction-site calculated MOPAC program. This fundamental approach was like that of explaining chemical reactions. The difference was electron localization in chromatography or electron transfer in a chemical reaction.
ARTICLE | doi:10.20944/preprints202009.0020.v1
Subject: Chemistry, Applied Chemistry Keywords: Omega-3 ethyl esters; monkfish liver oil; COSMO-RS, fungal resting cells; selectivity.
Online: 2 September 2020 (03:13:05 CEST)
The search for economical and sustainable sources of PUFAs within the framework of the circular economy is encouraged by their proven beneficial effects on health. The extraction of monkfish liver oil (MLO) for the synthesis of omega-3 ethyl esters was performed evaluating two blending systems and four green solvents. Moreover, the potential solubility of the MLO in green solvents was studied using the predictive simulation software COSMO-RS. The production of the ethyl esters was performed by one or two step reactions. Novozym 435, two resting cells (Aspergillus flavus and Rhizopus oryzae) obtained in our laboratory and mix of them were used as biocatalysts in a solvent-free system. The yields for Novozym 435, R. oryzae and A. flavus in the one-step esterification were 63%, 61% and 46%, respectively. The hydrolysis step in the two-step reaction led to 83%, 88% and 93% of free fatty acids (FFA) for Novozym 435, R. oryzae and A. flavus respectively. However, Novozym 435 showed the highest yield in the esterification step (85%) followed by R. oryzae (65%) and A. flavus (41%). Moreover, selectivity in front of polyunsaturated fatty acids of R. oryzae lipase was evidenced, since it did slightly esterified docosahexaenoic acid (DHA) in all the esterification reactions tested.
Mon, 31 August 2020
Subject: Chemistry, Medicinal Chemistry Keywords: cannabis; cannabinergic; drug; FDA-approved; medical conditions; pharmaceutical-grade; phytocannabinoid
Online: 31 August 2020 (10:38:32 CEST)
Despite the surge in the research of cannabis chemistry and its biological and medical activity, only a few cannabis-based pharmaceutical-grade drugs have been developed and marketed to date. Not many of these drugs are Food and Drug Administration (FDA)-approved and some are still going through regulation processes. Active compounds including cannabinergic compounds (i.e., molecules targeted to modulate the endocannabinoid system) or analogs of phytocannabinoids (cannabinoids produced by the plant) may be developed into single-molecule drugs. However, since in many cases treatment with whole plant extract is preferred over treatment with a single purified molecule, some more recently developed cannabis-derived drugs contain several molecules. Different combinations of active plant ingredients (API) from cannabis with proven synergy may be identified and developed as drugs to treat different medical conditions. However, possible negative effects between cannabis compounds should also be considered, as well as the effect of the cannabis treatment on the endocannabinoid system. FDA registration of single, few or multiple molecules as drugs is a challenging process and certain considerations that should be reviewed in this process, including issues of drug-drug interactions, are also discussed here.
ARTICLE | doi:10.20944/preprints202008.0713.v1
Subject: Chemistry, Food Chemistry Keywords: NMR; alcoholic beverages; ethanol; methanol; acetaldehyde; screening; validation; food control; PULCON
Online: 31 August 2020 (06:21:35 CEST)
Due to legal regulations, the rise of globalised (online) commerce and the need for public health protection, the analysis of spirits (alcoholic beverages > 15 % vol) is a task with growing importance for governmental and commercial laboratories. In this article a newly developed method using nuclear magnetic resonance (NMR) spectroscopy for the simultaneous determination of 15 substances relevant for the quality and authenticity assessment of spirits is described. The new method starts with a simple and rapid sample preparation and does not need an internal standard. For each sample a group of 1H-NMR spectra is recorded, among them a 2D spectrum for analyte identification and 1D spectra with suppression of solvent signals for quantification. Using the Pulse Length Based Concentration Determination (PULCON) method, concentrations are calculated from curve fits of the characteristic signals for each analyte. The optimisation of the spectra, their evaluation and the transfer of the results are done fully automatically. Glucose, fructose, sucrose, acetic acid, citric acid, formic acid, ethyl acetate, ethyl lactate, acetaldehyde, ethanol, methanol, n-propanol, isobutanol, isopentanol, 2-phenylethanol and 5-(hydroxymethyl)furfural (HMF) can be quantified with an overall accuracy better than 8 %. This new NMR-based targeted quantification method enables the simultaneous and efficient quantification of relevant spirits ingredients in their typical concentration ranges in one process with good accuracy. It has proven to be a reliable method for all kinds of spirits in routine food control.
COMMUNICATION | doi:10.20944/preprints202008.0701.v1
Subject: Chemistry, Chemical Engineering Keywords: carbon dioxide; molybdenum carbide; methanol; copper; alkali; dopant
Online: 31 August 2020 (05:03:06 CEST)
Mitigation of Anthropogenic CO2 emissions possess a major global challenge for modern societies. Herein catalytic solutions are meant to play a key role. Among the different catalysts for CO2 conversion Cu supported on molybdenum carbide is receiving increasing attention. Hence, in the present communication we show the activity, selectivity and stability of fresh-prepared -Mo2C catalysts and compare the results with those of Cu/Mo2C, Cs/Mo2C and Cu/Cs/Mo2C in CO2 hydrogenation reactions. The results showed that all the catalysts were active and the main reaction product was methanol. The results showed that copper-cesium and molybdenum effectively interact and that cesium promoted the formation of metallic Mo. While, the incorporation of copper is positive to improve the activity and selectivity to methanol, the presence of Mo0 phase was detrimental for the conversion and selectivity. Moreover, the catalysts promoted by cesium underwent redox surface transformations during the reaction that diminished their catalytic performance. The molybdenum phase in Cu/Mo2C changes during reaction leading to metallic molybdenum and tuning the catalytic activity.
ARTICLE | doi:10.20944/preprints202008.0690.v1
Subject: Chemistry, General & Theoretical Chemistry Keywords: Theopapuamides A-D; Virtual Screening; Chemoinformatics; Conceptual DFT; Computational Peptidology; Bioavailability; Bioactivity Scores; ADMET
Online: 31 August 2020 (03:57:38 CEST)
This work presents the results of a computational study of the chemical reactivity and bioactivity properties of the members of the Theopapuamides A-D family of marine peptides by making use of our own proposed methodology named Computational Peptidology (CP) that has been successfully considered in previous studies of this kind of molecular systems. CP allowed for the determination of the global and local descriptors that come from Conceptual Density Functional Theory (CDFT) that can give an idea of the chemical reactivity properties of the marine natural products under study which are already known to be related to their bioactivity. At the same time, the validity of the procedure based on the adoption of the KID (Koopmans in DFT) technique as well as the MN12SX/Def2TZVP/H2O model chemistry has been successfully verified. Together with several Chemoinformatic tools that can be used for the improvement of process of Virtual Screening, some additional properties of these marine peptides were identified related to their ability to behave as useful drugs. With the further object of analyzing their bioactivity some parameters of usefulness for future QSAR studies, their predicted biological targets and the the ADMET (Absorption, Distribution, Metabolism, Excretion and Toxicity) parameters related to the Theopapuamides A-D pharmacokinetics are also reported.
Sun, 30 August 2020
ARTICLE | doi:10.20944/preprints202008.0667.v1
Subject: Chemistry, Medicinal Chemistry Keywords: Ovarian cancer; drug resistance; apoptosis; proteomics; combination; cytotoxicity; artemisinin; oleanolic acid; platinum drugs; cisplatin
Online: 30 August 2020 (12:06:32 CEST)
Background: In the present study, cisplatin, artemisinin and oleanolic acid were evaluated alone and in combination, on human ovarian A2780, A2780ZD0473R and A2780cisR cancer cell lines with aim of overcoming cisplatin resistance and side effects. Methods: Cytotoxicity was assessed by MTT reduction assay. CI values were used as a measure of combined drug effect. MALDI TOF/TOF MS/MS and 2-DE gel electrophoresis were used to identify protein biomarkers in ovarian cancer and to evaluate combination effects. Results: Synergism from combinations was dependent on concentration and sequence of administration. Generally, bolus was most synergistic. 49 proteins differently expressed by 2 ≥ fold were: CYPA, EIF5A1, Op18, p18, LDHB, P4HB, HSP7C, GRP94, ERp57, mortalin, IMMT, CLIC1, NM23, PSA3,1433Z, and HSP90B were down-regulated, whereas hnRNPA1, hnRNPA2/B1, EF2, GOT1, EF1A1, VIME, BIP, ATP5H, APG2, VINC, KPYM, RAN, PSA7, TPI, PGK1, ACTG and VDAC1 were up-regulated, while TCPA, TCPH, TCPB, PRDX6, EF1G, ATPA, ENOA, PRDX1, MCM7, GBLP, PSAT, Hop, EFTU, PGAM1, SERA and CAH2 were not-expressed in A2780cisR cells. The proteins were found to play critical roles in cell cycle regulation, metabolism and biosynthetic processes and drug resistance and detoxification. Conclusion: Results indicate that appropriately sequenced combinations of cisplatin with ART and OA may provide a means to reduce side effects and circumvent platinum resistance.
Thu, 27 August 2020
ARTICLE | doi:10.20944/preprints202008.0600.v1
Subject: Chemistry, Organic Chemistry Keywords: lipase; biocatalysis; Wieland-Miescher ketone; biocatalyst screening; amylase; peptidase; enantiomeric excess; Robinson Annulation
Online: 27 August 2020 (08:37:44 CEST)
Lipases, a versatile class of biocatalysts, have been shown to function in non-aqueous media/organic solvents and to possess promiscuous catalytic activity for a wide range of organic transformations. In this study, we explore the biocatalytic properties of a library of commercially available lipases by screening them for catalysis of a one-pot synthesis of Wieland-Miescher Ketone, an important intermediate in the synthesis of biologically active compounds such as steroids and terpenoids, from methyl vinyl ketone and 2-methyl-1,3-cyclohexanedione. As a direct outgrowth of this screen, we have created an optimized procedure for Wieland-Miescher Ketone (WMK) synthesis using crude lipase preparations, characterizing both reaction yield and enantiomeric excess. We have also identified principal components of the crude lipase mixture through proteomics and present evidence for a non-lipolytic origin of the observed catalysis. Finally, using the optimized conditions developed in this study, we propose a general absorbance-based screening methodology for assessing biocatalytic potential of crude enzyme preparations for synthesis of WMK.
ARTICLE | doi:10.20944/preprints202008.0599.v1
Subject: Chemistry, Physical Chemistry Keywords: polypropylene; suspension grafting; melt-blown spinning; adsorption; aniline
Online: 27 August 2020 (08:27:29 CEST)
This paper uses polypropylene (PP) as the matrix and acrylic acid (AA) and maleic anhydride (MAH) as functional monomers to prepare PP-g-(AA-MAH) fibers by suspension grafting and melt-blown spinning technology that are easy to industrially scale-up. The fibers can be used to adsorb aniline from wastewaters. Results showed that the grafting ratio reached the maximum of 12.47%. The corresponding optimal conditions were grafting time of 3h, AA : MAH = 0.75, total monomer content of 55%, benzoyl peroxide 1.4%, xylene concentration of 6 mL/g PP, and deionized water content of 8 mL/g PP. Owing to its good fluidity and thermal stability, the product of suspension grafting can be used for melt-blown spinning. Infrared spectroscopic and nuclear magnetic resonance spectroscopic analyses indicated that AA and MAH were successfully grafted onto PP fibers. After grafting, the hydrophilicity of PP-g-(AA-MAH) fiber increased. Therefore, it had higher adsorptivity for aniline and the adsorption capacity could reach 42.2 mg/g at 45 min. Moreover, the PP-g-(AA-MAH) fibers showed good regeneration performance.
Wed, 26 August 2020
ARTICLE | doi:10.20944/preprints202008.0564.v1
Subject: Chemistry, Electrochemistry Keywords: Li-ion battery; computer simulation; numerical method; software
Online: 26 August 2020 (07:45:40 CEST)
This code provides computational facilities to simulate current versus time during the charging of Li-ion cells at desire constant voltage by considering multiscale physical phenomena. This code only considers a powder of active materials (at microscale or nanoscale) and a small part of electrolyte around it as a half cell. Then it is extended to a complete cell by applying correct boundary conditions. This code is very useful by modifying code parameters to understand the effect of the complex shape of active materials powder (surface area and powder size), kind of electrolyte, and the applied voltages on the charging response of Li-ion cell. As a summary, a microscale approach to the design of Li-ion cells has been provided via this code.
Subject: Chemistry, Analytical Chemistry Keywords: Howard Flack; Flack Parameter; Structure Analysis; X-ray Crystallography
Online: 26 August 2020 (05:01:13 CEST)
The Flack Parameter is now almost universally reported for all chiral materials characterized by X-ray crystallography. It’s elegantly simplicity was an inspired development by Flack, and although the original algorithm for its computation has been strengthened by other workers, it remains an essential outcome for any crystallographic structure determination. As with any one-parameter metric, it needs to be interpreted in the context of its standard uncertainty.
Tue, 25 August 2020
Subject: Chemistry, General & Theoretical Chemistry Keywords: carbone complexes; carbido complexes; transition metal complexes; chemical bonding
Online: 25 August 2020 (04:16:15 CEST)
This review summarizes experimental and theoretical studies of transition metal complexes with two types of novel metal-carbon bonds. One type features complexes with carbones CL2 as ligands, where the carbon(0) atom has two electron lone pairs which engage in double (σ and π) donation to the metal atom [M] CL2. The second part of this review reports complexes which have a neutral carbon atom C as ligand. Carbido complexes with naked carbon atoms may be considered as endpoint of the series [M]-CR3 → [M]-CR2 → [M]-CR → [M]-C.
ARTICLE | doi:10.20944/preprints202008.0533.v1
Subject: Chemistry, Analytical Chemistry Keywords: sulfamethoxazole; differential pulse voltammograms; cyclic voltammetry; molybdenum; nanoparticle; TMP
Online: 25 August 2020 (03:24:09 CEST)
Manganese and Molybdenum oxides are well-known electro-catalysts in fuel cells systems; they are usually used as anodic materials for the oxidation of low molecular weight alcohols. The utilization of MoO2 and MnO2 as catalysts in the pharmaceutical analysis is not common yet an analytical method for the determination of Sulfamethoxazole (SMX) antibacterial agents in Pharmaceutical Dosage form is developed. The method is based on the voltammetric determination of SMX using modified glassy carbon electrode by molybdenum oxide. The two components are oxidized at the modified electrode surface with the development of current that is linearly proportional to their concentrations in the range of 7.04*10-7- 1*10-3 M for SMX. The oxidation reaction of the two components is pH-dependent, in which the buffer used is Britton-Robinson at pH = 7.00 where maximum peak current and maximum peak separation is obtained. The regression factors obtained from the calibration curves are 0.9790 for SMX and 0.9812 for TMP. The method of analysis was validated, where the limit of detection (LOD) and the limit of quantitation (LOQ) of SMX were calculated to be 1.44*10-4 M, 4.36*10-4 M and 1.27*10-4 M, 3.84*10-4 M respectively, The percentage recovery of both components was also calculated to 81 % for SMX.
Mon, 24 August 2020
ARTICLE | doi:10.20944/preprints202008.0524.v1
Subject: Chemistry, Organic Chemistry Keywords: Isoxazolines; nitrile oxide; 1,3-dipolar cycloaddition; antibacterial activity; antioxidant activity
Online: 24 August 2020 (10:03:22 CEST)
A series of derivatives of trans-3-(2,4,6-trimethoxy phenyl)-4,5-dihydro isoxazolo-4,5-bis(aroylcarbohydrazide) and of trans-3-(2,4,6-trimethoxyphenyl)4,5-dihydroisoxazolo-4,5-bis[carbonyl-(4’phenyl)thiosemi- carbazide (9) were synthesized from trans-3-(2,4,6-trimethoxyphenyl)-4,5-dihydro-4,5-bis(hydrazenocarbonyl) Isoxazole (8). The structures of the Compounds were elucidated by elemental and spectral (IR, NMR, and MS) analysis. The compound 9 show activity against some bacterial species. Whereas, no activity was observed for compounds 10a, 10b and 10c against all bacterial species. The antioxidant activity of new compounds has been screened. Compound 9 showed higher antioxidant activity using the DPPH and ATBS method.
Online: 24 August 2020 (09:50:12 CEST)
Tetrathiolate zinc fingers are potential targets of oxidative assault under cellular stress conditions. We used the synthetic 37-residue peptide representing the tetrathiolate zinc finger domain of the DNA repair protein XPA, acetyl-DYVICEECGKEFMSYLMNHFDLPTCDNCRDADDKHK-amide (XPAzf) as a working model to study the reaction of its Zn(II) complex (ZnXPAzf) with hydrogen peroxide and S-nitrosoglutathione (GSNO), as oxidative and nitrosative stress agents, respectively. We also used the Cd(II) substituted XPAzf (CdXPAzf) to assess the situation of cadmium assault, which is accompanied by oxidative stress. Using electrospray mass spectrometry (ESI-MS), HPLC, and UV-vis and circular dichroism spectroscopies we demonstrated that even very low levels of H2O2 and GSNO invariably cause irreversible thiol oxidation and concomitant Zn(II) release from ZnXPAzf. In contrast, CdXPAzf was more resistant to oxidation, demonstrating the absence of synergy between cadmium and oxidative stresses. Our results indicate that GSNO cannot act as a reversible modifier of XPA, and rather has a deleterious effect on DNA repair.
Thu, 20 August 2020
ARTICLE | doi:10.20944/preprints202008.0438.v1
Subject: Chemistry, Organic Chemistry Keywords: acetylcholinesterase; antioxidant; Alzheimer; coumarin; selenazole
Online: 20 August 2020 (07:26:34 CEST)
Inhibition of acetylcholinesterase (AChE) enzyme is a known procedure to treat severe Alzheimer's disease through increasing the acetylcholine level in the brain and thus slowing down the progression of Alzheimer's symptoms. The approved medications are only considered as palliative and addressed some reported deficiencies. Therefore, the demand for safe and effective compounds is substantially increasing. A newly series of coumaryl 1,3-selenazoles derivatives was synthesized in four steps. Then, their antioxidant activities were evaluated using DPPH, ABTS cation radical scavenging assay and cupric reducing antioxidant capacities (CUPRAC). The anticholinesterase activities were evaluated using the Ellman method. Then, the docking studies were carried out to explain the possible correlation between in vitro anticholinesterase activity results and the ligand-receptor interactions. Ten new coumaryl 1,3-selenazoles (5a-5d series and 6a-6f series) derivatives were successfully synthesized. The DPPH radical scavenging assay showed that all tested compounds have IC50 value > 200 μM, for ABTS cation radical scavenging assay the IC50 value > 1000 μM and for CUPRAC assay the IC50 value > 200 μM. Compound 5c was found to be the most active compound against AChE and BChE in its series with IC50 value for AChE is 99.76 μM and IC50 for BChE is 140.28 μM while 6b exhibited the most potent inhibition in its series with IC50 value for AChE is 56.01 μM and IC50 for BChE is 121.34 μM. Besides, the docking studies showed that compound 5c and 6b formed π-π stacking interaction with aromatic residues at the active site of AChE and BChE, which is responsible for inhibiting the enzymes. This shows that the synthesized compounds contain skeletal structures that can interact and inhibit within the enzymes active site.
ARTICLE | doi:10.20944/preprints202008.0427.v1
Online: 20 August 2020 (05:40:51 CEST)
The direct Cr (VI) reduction process by oxalic acid was conducted and the results showed that the Cr (VI) was efficiently reduced by oxalic acid at high reaction temperature and high dosage of oxalic acid. The reduced product, Cr (III), was easily generated stable complex compounds (Cr(HC2O4)3) with oxalate, which displayed a negative effect on the reduction process. The high reaction temperature and high acidic medium could destroy the stable structure of a complex compound to release oxalate, and facilitate the reduction of Cr (VI). Generally, the present study provided a versatile strategy for Cr (VI) reduction, exhibiting a bright application future for real wastewater treatment.
Mon, 17 August 2020
ARTICLE | doi:10.20944/preprints202008.0352.v1
Subject: Chemistry, Organic Chemistry Keywords: geobacillus thermocatenolatus; lipases; ethanolysis; ionic liquids; kinetic resolution; mandelic acid
Online: 17 August 2020 (05:06:27 CEST)
Keywords: Geobacillus thermocatenolatus; lipases; ethanolysis; ionic liquids; kinetic resolution; mandelic acid.
ARTICLE | doi:10.20944/preprints202008.0351.v1
Subject: Chemistry, General & Theoretical Chemistry Keywords: discodermins A-H; chemical reactivity theory; conceptual DFT; global and local reactivity descriptors; pKa; bioavailability; bioactivity scores; ADME
Online: 17 August 2020 (04:45:58 CEST)
A methodology based on the concepts that arise from Density Functional Theory named Conceptual Density Functional Theory (CDFT) was chosen for the calculation of some global and local reactivity descriptors of the Discodermins A-H family of marine peptides through the consideration of the KID (Koopmans in DFT) technique that was successfully used in previous studies of this kind of molecular systems. The determination of active sites of the studied molecules for different kind of reactivities was achieved by resorting to some CDFT-based descriptors like the Fukui functions as well as the Parr functions derived from Molecular Electron Density Theory (MEDT). A few properties identified with their ability to behave as a drug and the bioactivity of the peptides considered in this examination were acquired by depending on a homology model by studying the correlation with the known bioactivity of related molecules in their interaction with various biological receptors. With the further object of analyzing their bioactivity some parameters of usefulness for future QSAR studies, their predicted biological targets and the the ADME (Absorption, Distribution, Metabolism, and Excretion) parameters related to the Discodermins A-H pharmacokinetics are also reported.
Thu, 13 August 2020
ARTICLE | doi:10.20944/preprints202008.0306.v1
Subject: Chemistry, Medicinal Chemistry Keywords: Glycyrrhiza uralensis; Glycyrol; Liquiritigenin; cholinesterases; human monoamine oxidases; kinetics; docking simulation.
Online: 13 August 2020 (12:11:26 CEST)
Eight compounds were isolated from the roots of Glycyrrhiza uralensis and tested for cholinesterase (ChE) and monoamine oxidase (MAO) inhibitory activities. Glycyrol (GC) effectively inhibited butyrylcholinesterase (BChE) and acetylcholinesterase (AChE) with IC50 values of 7.22 and 14.77 µM, respectively, and also moderately inhibited MAO-B (29.48 µM). Six of the other seven compounds only weakly inhibited AChE and BChE, whereas liquiritin apioside moderately inhibited AChE (IC50 = 36.68 µM). Liquiritigenin (LG) potently inhibited MAO-B (IC50 = 0.098 µM) and MAO-A (IC50 = 0.27 µM), and liquiritin, a glycoside of LG, weakly inhibited MAO-B (> 40 µM). GC was a reversible, noncompetitive inhibitor of BChE with a Ki value of 4.47 µM, and LG was a reversible competitive inhibitor of MAO-B with a Ki value of 0.024 µM. Docking simulations showed that the binding affinity of GC for BChE (-7.8 kcal/mol) was greater than its affinity for AChE (-7.1 kcal/mol), and suggested that GC interacted with BChE at Thr284 and Val288 by hydrogen bonds (distances: 2.42 and 1.92 Å, respectively) beyond the ligand binding site of BChE, but that GC did not form hydrogen bond with AChE. The binding affinity of LG for MAO-B (-8.8 kcal/mol) was greater than its affinity for MAO-A (-7.9 kcal/mol). These findings suggest GC and LG should be considered promising compounds for the treatment of Alzheimer’s disease with multi-targeting activities.
COMMUNICATION | doi:10.20944/preprints202008.0297.v1
Subject: Chemistry, Analytical Chemistry Keywords: cat urine; odor mitigation; odor; volatile organic compounds; emission; indoor air quality, solid-phase microextraction; SPME; diffusion; Micrococcus luteus
Online: 13 August 2020 (08:51:58 CEST)
Urination on carpet and subflooring can develop into persistent and challenging to mitigate odor. Very little or no information is published on how these VOCs change over time when urine is deposited on the carpet covering a plywood-type subflooring. This research has investigated the VOCs emitted from carpet+subflooring (control), carpet+subflooring sprayed with water (control with moisture), and cat urine-contaminated carpet+subflooring (treatment) over time (day 0 and 15). In addition, the effect of popular cleaning products on VOCs emitted and evaluated their efficacy in eliminating those indoor odors over time (day 0 and 15). Carpet-subflooring with all treatments were also contaminated with Micrococcus luteus, nonmotile obligate aerobe commonly found in household dust, to observe the impact of the aerobe on carpet-subflooring VOCs emission. VOCs emitted from carpet+subflooring receiving different treatments were collected from headspace using solid-phase microextraction (SPME). The VOCs were analyzed using a multidimensional gas chromatography-mass spectrometer attached to an olfactometry (GC-MS-O). Many common VOCs were released from the carpet on day one and day fifteen, specifically from urine contamination. Cleaning products were effective in masking several potent odors of cat urine contaminated carpet VOCs on day one but unable to remove the odor appeared on day 15 in most cases.
Wed, 12 August 2020
ARTICLE | doi:10.20944/preprints202008.0282.v1
Subject: Chemistry, Analytical Chemistry Keywords: cyanobacteria; cyanopeptides; eutrophication; harmful bloom; liquid chromatography tandem mass spectrometry; Global Natural Product Social networking (GNPS); Dereplication strategy.
Online: 12 August 2020 (10:15:46 CEST)
Man-made shallow fishponds in the Czech Republic have been facing a high eutrophication since 1950s. Anthropogenic eutrophication and feeding of fish have strongly affected the physico-chemical properties of water and its aquatic community composition leading to harmful algal bloom formation. In our current study, we have characterised the phytoplankton community across three hypertrophic ponds to assess the phytoplankton dynamics during the vegetation season. We microscopically identified and quantified 29 cyanobacterial taxa comprised of non-toxigenic and toxigenic species. Further, a detailed cyanopeptides (CNPs) profiling was performed using molecular networking analysis of liquid chromatography tandem mass spectrometry (LC–MS/MS) data coupled with dereplication strategy. This MS networking approach coupled with dereplication on online global natural product social networking (GNPS) web platform led us to putatively identify forty CNPs: fourteen anabaenopeptins, ten microcystins, five cyanopeptolins, six microginins, two cyanobactins, a dipeptide radiosumin, a cyclooctapeptide planktocyclin and epidolastatin12. We have applied the binary logistic regression to estimate the CNPs producer by correlating the GNPS data with the species abundance. Usage of The combination of molecular networking and dereplication on online global natural product social networking (GNPS) web platform has proved as a valuable approach for rapid and simultaneous detection of high number of peptides, and rapidly assessing the risk for harmful bloom.
Mon, 10 August 2020
REVIEW | doi:10.20944/preprints202008.0234.v1
Subject: Chemistry, Applied Chemistry Keywords: Photosynthesis; Photoelectrochemical Devices; Biohybrid; Synthetic Biology; Photochemistry; Photoelectrochemistry; Hydrogen Evolution
Online: 10 August 2020 (04:20:58 CEST)
Abstract: The biological process of photosynthesis was critical in catalyzing the oxygenation of Earth’s atmosphere 2.5 billion years ago, changing the course of development of life on Earth. Recently, the fields of applied and synthetic photosynthesis have utilized the light-driven protein-pigment supercomplexes central to photosynthesis for the photocatalytic production of fuel and other various valuable products. The reaction center Photosystem I is of particular interest in applied photosynthesis due to its high stability post-purification, non-geopolitical limitation, and its ability to generate the greatest reducing power found in Nature. These remarkable properties have been harnessed for the photocatalytic production of a number of valuable products in the applied photosynthesis research field. These primarily include photocurrents and molecular hydrogen as fuels. The use of artificial reaction centers to generate substrates and reducing equivalents to drive non-photoactive enzymes for valuable product generation has been a long-standing area of interest of the synthetic photosynthesis research field. In this review, we cover advances in these areas and further speculate synthetic and applied photosynthesis as photocatalysts for the generation of valuable products.
Sun, 9 August 2020
REVIEW | doi:10.20944/preprints202008.0223.v1
Subject: Chemistry, Inorganic & Nuclear Chemistry Keywords: Serum transferrin; endocytosis; nonferric metal ions; metal transport, bioavailability, and bioactivity; metal therapeutic function and toxicity
Online: 9 August 2020 (21:47:51 CEST)
Serum transferrin (sTf) plays a pivotal role in regulating iron biodistribution and homeostasis within the body. The molecular details of sTf Fe(III) binding, blood transport, and cellular delivery through transferrin receptor-mediated endocytosis are generally well-understood. Emerging interest exists in exploring sTf complexation of nonferric metals as it facilitates the therapeutic potential and toxicity of several of them. This review explores recent X-ray structural and physiologically relevant metal speciation studies to understand how sTf partakes in the bioactivity of key non-redox active hard Lewis acidic metals. It challenges preconceived notions of sTf structure function correlations that were based exclusively on the Fe(III) model by revealing distinct coordination modalities that nonferric metal ions can adopt and different modes of binding to metal-free and Fe(III)-bound sTf that can directly influence how they enter into cells and, ultimately, how they may impact human health. This knowledge informs on biomedical strategies to engineer sTf as a delivery vehicle for metal-based diagnostic and therapeutic agents in the cancer field. It is the intention of this work to open new avenues for characterizing the functionality and medical utility of nonferric-bound sTf and to expand the significance of this protein in the context of bioinorganic chemistry.
Wed, 5 August 2020
ARTICLE | doi:10.20944/preprints202008.0112.v1
Subject: Chemistry, Medicinal Chemistry Keywords: AKT/PI3K signaling pathway; apoptosis; human hepatocarcinoma HepG2 cells; migration activity; proliferation; oxidative stress; ROS level; uvaol
Online: 5 August 2020 (05:58:26 CEST)
Natural products have a significant role in the development of new drugs, being relevant the pentacyclic triterpenes extracted from Olea europaea. Anticancer effect of uvaol, a natural triterpene, has been scarcely studied. The aim of this study was to understand the anticancer mechanism of uvaol in HepG2 cell line. Cytotoxicity results showed a selectivity effect of uvaol with higher influence in HepG2 than WRL68 cells used as control. Uvaol presented anti-migratory capacity in HepG2, supported by the morphological changes and higher HSP-60 expression. This compound also induced arrest in G0/G1 phase and an increase in apoptosis rate. These results are supported by decreased Bcl-2 expression and down-regulation of AKT/PI3K signaling pathway. A reduction in reactive oxygen species levels in HepG2 cells was observed. Altogether, results showed anti-proliferative and pro-apoptotic effect of uvaol on hepatocellular carcinoma, constituting an interesting challenge in the development of new treatments against this type of cancer.
Tue, 4 August 2020
ARTICLE | doi:10.20944/preprints202008.0077.v1
Subject: Chemistry, Medicinal Chemistry Keywords: anti-oxidant activity; anti-oxidant enzymes, anti-proliferative activity; maslinic acid; melanoma; Olea europaea; ROS levels
Online: 4 August 2020 (04:57:13 CEST)
Maslinic acid (MA) is a natural triterpene from Olea europaea whose pharmacological functions have been showed. The objective of this study was to examine MA effect on cell viability (by MTT assay), reactive oxygen species (ROS levels, by flow cytometry) and key anti-oxidant enzyme activities (by spectrophotometry) in murine skin melanoma (B16F10) cells compared to healthy cells (A10). MA induced cytotoxic effects in cancer cells (IC50 42 µM) whereas no effect was found in A10 cells treated with MA (up to 210 µM). In order to produce a stress situation in cells, 0.15 mM of H2O2 were added. Under stressful conditions, MA protected both cell lines against oxidative damage, decreasing intracellular ROS, being higher in B16F10 than in A10 cells. The treatment with H2O2 and without MA produced different responses in anti-oxidant enzymes activities depending on cell line. In A10 cells, all enzymes were up-regulated, but in B16F10 cells only superoxide dismutase, glutathione S-transferase and glutathione peroxidase increased their activities. MA restored the enzyme activities to similar levels than control group in both cell lines, highlighting that in A10 cells the highest MA doses induced values lower than control. Overall, these findings demonstrate the great anti-oxidant capacity of MA.
Sun, 2 August 2020
ARTICLE | doi:10.20944/preprints202008.0052.v1
Subject: Chemistry, Food Chemistry Keywords: Spray Drying; Vitamin C; Phenolic Compounds; Preservation; Modeling; Optimization
Online: 2 August 2020 (18:22:59 CEST)
Umbu is a tropical fruit with high content of bioactive compounds. However, maturation causes significant losses on nutrient density reducing the nutritional value of this highly appreciated fruit. Thus, the objective of the present work was to encapsulate the Umbu fruit bioactive compounds using spray drying and identify the variables affecting the biomolecules preservation. A Box-Behnken experimental design with 3 factors was set varying inlet temperature, atomization flow rate, and maltodextrin concentration for process otimization. Then the powder physicochemical and chemical properties were characterized, and results were modeled using a polynomial equation. Results revealed that the droplet size and maltodextrin concentration had a significant influence on the conservation of the biomolecules. Drying kinetics favoring fast formation of a particle crust increases encapsulation efficiency. Bioactive compounds retention was achieved by increasing maltodextrin even at high temperatures, where a matrix is formed hindering chemical degradation. Process optimization was validated and revealed low inlet temperatures (122ºC), high atomization flow rate (5kg/h) and high maltodextrin concentration (20%) to be the most desirable conditions for bioactive compounds retention.
ARTICLE | doi:10.20944/preprints202008.0025.v1
Subject: Chemistry, Analytical Chemistry Keywords: HPLC method; Curcumin; Quercetin; Thermal analysis; Nanoemulsion
Online: 2 August 2020 (12:15:13 CEST)
Biphasic oily/water nanoemulsions have been proposed as delivery systems for the intranasal administration of curcumin (CUR) and quercetin (QU), due to their high drug entrapment efficiency, the possibility of simultaneous drug administration and protection of the encapsulated compounds from the degradation. To better understand the physicochemical and biological performance of the selected formulation simultaneously co-encapsulating CUR and QU, a stability test of the compounds mixture was firstly carried out using X-ray powder diffraction and thermal analyses, such as differential scanning calorimetry (DSC) and thermogravimetric analyses (TGA). The determination and quantification of the encapsulated active compounds was then required being an essential tool for the development of innovative nanomedicines. Thus, a new HPLC–UV/Vis method for the simultaneous determination of CUR and QU in the nanoemulsions and their evaluation in stability studies in simulated biological fluids was developed and validated. The X-ray diffraction analyses demonstrated that no interaction between the mixture of active ingredients, if any, is strong enough to take place in the solid state. Moreover, the thermal analysis demonstrated that the CUR and QU are stable in the nanoemulsion production temperature range. The proposed analytical method for the simultaneous quantification of the two actives was selective and linear for both compounds in the range of 0.5 – 12.5 µg/mL (R2 > 0.9997), precise (RSD below 3%), robust and accurate (recovery 100 ± 5 %). The method was validated in accordance with ICH Q2 R1 “Validation of Analytical Procedures” and CDER-FDA 2validation of chromatographic methods” guideline. Furthermore, the low detection (LOD < 0.005 µg/mL for CUR and <0.14 µg/mL for QU) and quantification limits (LOQ < 0.017 µg/mL for CUR and < 0.48 µg/mL for QU) of the method were suitable for the application to drug release and permeation studies planned for the development of the nanoemulsions. The method was then applied for the determination of nanoemulsions CUR and QU encapsulation efficiencies (> 99%), as well as for the stability studies of the two compounds in simulated biological fluids over time. The proposed method represents, to our knowledge, the only method for the simultaneous quantification of CUR, and QU in nanoemulsions.
Fri, 31 July 2020
ARTICLE | doi:10.20944/preprints202007.0748.v1
Subject: Chemistry, Applied Chemistry Keywords: Rosmarinus officinalis L.; surface and subsurface drip irrigation; bentonite; Hundz conditioner; essential oil
Online: 31 July 2020 (13:43:12 CEST)
A relevant improvement of the cultivar conditions of Rosmarinus officinalis L. in desert areas was achieved by a specific combination between irrigation system and soil conditioner. A drastic reduction of water employment was obtained without affect the quality of the plants, determined by monitoring growth parameters and essential oil characteristics. In particular, the effect of surface and subsurface drip irrigation systems and different soil conditioners on growth parameters, yield, and essential oil constituents of rosemary plant was assessed. Field experiments at the Agricultural Research Station (Al-Adlya farm), SEKEM group Company, El-Sharkiya Governorate, Egypt, conducted over the two seasons revealed the effectiveness of the subsurface irrigation system in obtaining better performances, especially in terms of water saving. The combination of subsurface irrigation and the conditioner Hundz soil with bentonite showed the maximum mean values of growth characters compared with other soil amendments during both seasons. The possibility to employ a water-saving irrigation system as the subsurface one without any drawback in the resulting plants was also explored in terms of molecular composition. GC-MS analysis of the essential oil extracted from plants growth under different irrigation conditions revealed a comparable composition in both cases. The goodness of the most performing system was also confirmed by the comparable yield of the essential oil.
ARTICLE | doi:10.20944/preprints202007.0742.v1
Subject: Chemistry, General & Theoretical Chemistry Keywords: KID protocol; Global Reactivity; Conceptual DFT; Kopmans’ Theorem; Mo–oxo Complexes; Hydrogen production
Online: 31 July 2020 (10:09:50 CEST)
The KID (Koopmans in DFT) procedure usually applies in organic molecules of the closed–shell type. We used the KID procedure in an open–shell system for the first time to choose the most suitable density functional to compute global and local reactivity descriptors coming from the Conceptual Density–Functional Theory. From a set of 18 density functionals spread from the second until the fourth rung of the Jacob’s ladder: BP86, B97-D, BLYP, CAM-B3LYP, M06-L, M11-L, MN12-L, B3LYP, PBE0, N12-SX, M06-2X, M11, MN12-SX, CAM-B3LYP, LC-ωHPBE, ωB97X-D, APFD, MN15 and MN15-L, we concluded that CAM-B3LYP provides the best outcome.
ARTICLE | doi:10.20944/preprints202007.0729.v1
Subject: Chemistry, Applied Chemistry Keywords: scientometric analysis; catalysis; bibliometric indicators; catalysis research; catalysis journals
Online: 31 July 2020 (04:36:20 CEST)
The outcomes of the present scientometric analysis of research in catalysis provide chemistry and catalysis scholars with a closer bibliometric knowledge of an old and central field of chemical research which is being reshaped by fundamental and technological advances spanning from single-atom heterogeneous catalysis to flow chemistry. Improving and widening research and education in catalysis is a strategic need for national economies. Four research policy guidelines aimed at fostering progress in catalysis research and education conclude the study.
Wed, 29 July 2020
ARTICLE | doi:10.20944/preprints202007.0687.v1
Subject: Chemistry, Applied Chemistry Keywords: Gamma-ray, Mutant, Rose, Volatile compounds, GC-MS
Online: 29 July 2020 (09:46:55 CEST)
Roses are one of the most important floricultural crops, and their essential oils have long been used for cosmetics and aromatherapy. We investigated the volatile compound compositions of 12 flower-color mutant variants and their original cultivars. Twelve rose mutant genotypes were developed by treatment with 70 Gy of 60Co gamma irradiation of six commercial rose cultivars. Essential oils from the flowers of the 18 genotypes were analyzed by gas chromatography–mass spectrometry. Seventy-seven volatile compounds were detected, which were categorized into five classes: hydrocarbons, terpenoids, alcohols, esters, and others. Hydrocarbons, alcohols, and esters were major components in all rose flowers. The mutant genotypes CR-S8 and CR-S9 showed higher contents of hydrocarbons than the original cultivar. In addition, CR-S1, CR-S3, and CR-S4 mutant genotypes showed higher ester contents than their original cultivar. Nonacosane, 2-methylhexacosane, and 2-methyltricosane were major volatile compounds among all genotypes. Hierarchical cluster analysis of the rose genotypes gave four groups according to grouping among the 77 volatile compounds. These findings will be useful for the selection of rose genotypes with improved volatile compounds.
Sun, 26 July 2020
REVIEW | doi:10.20944/preprints202007.0649.v1
Subject: Chemistry, Physical Chemistry Keywords: Glycerol polymerization; Polyglycerol; Alkaline catalyst; Mechanism
Online: 26 July 2020 (17:36:16 CEST)
Polyglycerols (PGs) are biocompatible and highly functional polyols with a wide range of applications, such as emulsifiers, stabilizers, antimicrobial agents, in many industries including cosmetics, food, plastic and biomedical. The demand increase for biobased PGs encourages researchers to develop new catalytic systems for glycerol polymerization. This review focuses on alkaline homogeneous and heterogeneous catalysts. The performances of the alkaline catalysts are compared in terms of conversion and selectivity, and their respective advantages and disadvantages are commented. While homogeneous catalysts exhibit a high catalytic activity, they cannot be recycled and reused, whereas solid catalysts can be partially recycled. The key issue for heterogenous catalytic systems, which is unsolved so far, is linked to their instability due to partial dissolution in the reaction medium. Further, this paper also reviews the proposed mechanisms of glycerol polymerization over alkaline-based catalysts and discuss the various operating conditions with an impact on the performances. More particularly, temperature and amount of catalyst proved to have a significant influence on glycerol conversion and on its polymerization extent.
ARTICLE | doi:10.20944/preprints202007.0631.v1
Subject: Chemistry, Physical Chemistry Keywords: room temperature phosphorescence; organic molecule; excited state dynamics; time-resolved photoluminescence spectroscopy; photostability
Online: 26 July 2020 (02:44:23 CEST)
Room-temperature phosphorescent (RTP) materials have been attracted tremendous interest owing to their unique material characteristics and potential applications for state-of-the-art optoelectronic devices. Recently, we have reported a synthesis and fundamental photophysical properties of new RTP materials based on benzil, i.e., fluorinated monobenzil derivative and fluorinated and non-fluorinated bisbenzil derivative analogues [Yamada, S. et al, Beilstein J. Org. Chem. 2020, 16, 1154–1162.]. To further understand their RTP properties, here we investigated the excited-state dynamics and photostability of the derivatives by means of time-resolved and steady-state photoluminescence spectroscopies. For these derivatives, clear RTP emissions with lifetimes on the microsecond timescale were identified. Among them, the monobenzil derivative was found to be the most efficient RTP material, showing both the longest lifetime and highest amplitude RTP emission. Time-resolved photoluminescence spectra measured at 77 K and density functional theory calculations revealed the existence of a second excited triplet state in the vicinity of the first excited singlet state for the monobenzil derivative, indicative of the presence of a fast intersystem crossing pathway. A discussion of the correlation between the excited state dynamics, emission properties, and conformational flexibility of the three derivatives is presented.
Sat, 25 July 2020
HYPOTHESIS | doi:10.20944/preprints202007.0610.v1
Subject: Chemistry, Organic Chemistry Keywords: symmetry breaking; dihydroxyacetone phosphate; sn-glycerol-1-phosphate dehydrogenase; sn-glycerol-3-phosphate dehydrogenase; membrane evolution
Online: 25 July 2020 (15:35:55 CEST)
Either stereo reactants or stereo catalysis from achiral or chiral molecules are prerequisite to obtain pure enantiomeric lipid derivatives. We reviewed a few plausible organic syntheses of phospholipids under prebiotic conditions with a special attention to the starting materials as pro-chiral dihydroxyacetone and dihydroxyacetone phosphate (DHAP), which are the key molecules to break symmetry in phospholipids. The advantages of homochiral membranes compared to those of heterochiral membranes were analysed in term of specific recognition, optimal functions of enzymes, membrane fluidity and topological packing. All biological membranes contain enantiomeric lipids in modern bacteria, eukarya and archaea. The contemporary archaea, comprising of methanogens, halobacteria and thermoacidophiles are living under extreme conditions reminiscent of primitive environment and may indicate the origin of one ancient evolution path of lipid biosynthesis. The analysis of lipid metabolism reveals that all modern cells including archaea synthetize enantiomeric lipid precursors from prochiral DHAP. sn-glycerol-1-phosphate dehydrogenase (G1PDH), usually found in archaea, catalyses the formation of sn-glycerol-1-phosphate (G1P), while sn-glycerol-3-phosphate dehydrogenase (G3PDH) catalyses the formation of sn-glycerol-3-phosphate (G3P) in bacteria and eukarya. The selective enzymatic activity seems to be the main strategy that evolution retained to obtain enantiomeric pure lipids. The occurrence of two genes encoding for G1PDH and G3PDH, served to build up an evolution tree and the basis of our review focusing on the evolution of these two genes. Gene encoding for G3PDH in Eukarya may originate from G3PDH gene found in rare archaea indicating that archaea appeared earlier in the evolution tree than eukarya. Archaea and bacteria evolved probably separately, due to their distinct respective genes coding for G1PDH and G3PDH. The suggested hypothesis is that catalysis of homochiral G1P or G3P from DHAP are more efficient than those leading to racemic G1P and G3P, since there are no enzymes able to synthesize racemic G1P and G3P from DHAP. We propose that G1PDH or G3DPH, which are not “image mirror enzymes” but belonging to distinct family of proteins, emerged separately during evolution. They were probably selected for their efficient catalytic activities during evolution from large libraries of vesicles containing various biopolymers, including amino acids, carbohydrates, nucleic acids, lipids, and meteorite components to induce chemical imbalance.
Thu, 23 July 2020
ARTICLE | doi:10.20944/preprints202007.0562.v1
Subject: Chemistry, Analytical Chemistry Keywords: Brasilonema; Anabaenopeptins; hexapeptides; tryptophan-containing peptides; molecular networking; antiproliferative activity
Online: 23 July 2020 (12:40:38 CEST)
Heterocytous cyanobacteria are among the most prolific source of bioactive secondary metabolites, including anabaenopeptins (APTs). A terrestrial filamentous Brasilonema sp. CT11 collected in Costa Rica bamboo forest, as black mat was studied using a multidisciplinary approach: genome mining and HPLC-HRMS/MS coupled with bionformatic analyses. Herein, we report the nearly complete genome consisting 8.79 Mbp with a GC content of 42.4%. Moreover, we report on three novel tryptophane-containing APTs; anabaenopeptin 788 (1), anabaenopeptin 802 (2) and anabaenopeptin 816 (3). Further, the structure of two homologues, i.e., anabaenopeptin 802 (2a) and anabaenopeptin 802 (2b) was determined by spectroscopic analysis (NMR and MS). Both compounds were shown to exert weak to moderate antiproliferative activity against HeLa cell lines. This study also provides the unique and diverse potential of biosynthetic gene clusters and an assessment of the predicted chemical space yet to be discovered from this genus.
ARTICLE | doi:10.20944/preprints202007.0561.v1
Subject: Chemistry, Electrochemistry Keywords: perfluorooctanoic acid; emerging contaminant; defluorination; platinum; electro-oxidation
Online: 23 July 2020 (12:36:19 CEST)
Perfluorooctanoic acid (PFOA), C7F15COOH, has been widely employed over the past fifty years, causing an environmental problem due to its dispersion and low biodegradability. Furthermore, the high stability of this molecule, conferred by the high strength of the C-F bond makes it very difficult to remove. In this work, electrochemical techniques are applied for PFOA degradation in view to study the influence of the cathode on defluorination. For this purpose, boron doped diamond (BDD), Pt, Zr and stainless steel have been tested as cathodes working with BDD anode at low electrolyte concentration (3.5 mM) to degrade PFOA at 100 mg/L. Among these cathodic materials, Pt improves the defluorination reaction. The electro-degradation of a PFOA molecule starts by a direct exchange of one electron at the anode and then follows a complex mechanism involving reaction with hydroxyl radicals and adsorbed hydrogen on the cathode. It is assumed that Pt acts as an electrocatalyst, enhancing PFOA defluorination by the reduction reaction of perfluorinated carbonyl intermediates on the cathode. The defluorinated intermediates are then more easily oxidized by HO• radicals. Hence, high mineralization (xTOC: 76.1%) and defluorination degrees (xF-: 58.6%) were reached with Pt working at current density j = 7.9 mA/cm2. This BDD-Pt system reaches a higher efficiency in terms of defluorination for a given electrical charge than previous works reported in literature. Influence of the electrolyte composition and initial pH are also explored.
ARTICLE | doi:10.20944/preprints202007.0558.v1
Subject: Chemistry, Medicinal Chemistry Keywords: COVID-19; protein protein interactions; virtual screening; docking; molecular dynamics; zinc
Online: 23 July 2020 (12:27:23 CEST)
The outbreak of the novel coronavirus SARS-CoV-2, the causative agent of COVID-19, has caused a global health crisis. Unfortunately, only a few treatments have proved to be effective, and their worldwide distribution remains as a challenge. Due to the urgency of the situation, drug repurposing remains as the fastest way to identify possible therapeutic options. Recent studies have shown that the stabilization of non-native Protein-Protein Interactions (PPIs) of the nucleocapsid protein of MERS coronavirus is a valid strategy to inhibit viral replication, but no study up to date has been done in SARS-CoV-2. In this work, a novel protocol for the discovery of PPIs stabilizers is presented and applied to SARS-CoV-2 N protein with a drug repurposing approach. This enabled us to identify that catechin, a structural motif present in widely distributed natural products, might be a privileged scaffold for this type of stabilization. Since many of the compounds presented in this work are generally considered nutraceuticals and have also been exhaustively studied, even though some of them contain PAINS substructures, could be good candidates for the SARS-CoV-2 nucleocapsid inhibition and be considered for further in vitro testing against COVID-19.
Tue, 21 July 2020
ARTICLE | doi:10.20944/preprints202007.0495.v1
Subject: Chemistry, Medicinal Chemistry Keywords: In silico target prediction; dihydrochalcones; SEA; SwissTargetPrediction; SuperPred; polyphamracology; virtual screening
Online: 21 July 2020 (13:43:40 CEST)
Natural products comprise a rich reservoir for innovative drug leads and are a constant source of bioactive compounds. To find pharmacological targets for new or already known natural products using modern computer-aided methods is a current endeavor in drug discovery. Nature’s treasures, however, could be used more effectively. Yet, reliable pipelines for large scale target prediction of natural products are still rare. We have developed an in silico workflow consisting of four independent, stand-alone target prediction tools and evaluated its performance on dihydrochalcones (DHCs) – a well-known class of natural products. Thereby, we revealed four previously unreported protein targets for DHCs, namely 5-lipoxygenase, cyclooxygenase-1, 17β- hydroxysteroid dehydrogenase 3, and aldo-keto reductase 1C3. Moreover, we provide a thorough strategy on how to perform computational target prediction and guidance on using the respective tools.
ARTICLE | doi:10.20944/preprints202007.0490.v1
Subject: Chemistry, Inorganic & Nuclear Chemistry Keywords: Carbodiphosphorane; Phosphorus Ylides; Pincer Ligands; Coordination Chemistry; Cu(I) complex; Photoluminescence
Online: 21 July 2020 (12:52:11 CEST)
A series of dinuclear copper(I) N,C,N- and P,C,P-carbodiphosphorane (CDP) complexes using multidentate ligands CDP(Py)2 (1) and (CDP(CH2PPh2)2 (13) have been isolated and characterized. Detailed structural information was gained by single crystal XRD analyses of nine representative examples. The common structural motive is the central double ylidic carbon atom with its characteristic two lone-pairs involved into binding of two geminal L-Cu(I) fragments at Cu-Cu distances in the range 2.55 – 2.67 Å. In order to enhance conformational rigidity within the characteristic Cu-C-Cu triangle, two types of chelating side arms were symmetrically attached to each phosphorus atom: two 2-pyridyl functions in ligand CDP(Py)2 (1) and its dinuclear copper complexes 2-9 and 11, as well as two diphenylphosphinomethylene functions in ligand CDP(CH2PPh2)2 (13) and its di- and mononuclear complexes 14-18. Neutral complexes were typically obtained via reaction of 1 with Cu(I) species CuCl, CuI, and CuSPh or via salt elimination reaction of [(CuCl)2(CDP(Py)2] (2) with sodium carbazolate. Cationic Cu(I) complexes were prepared upon treating 1 with two equivalents of [Cu(NCMe)4]PF6, followed by the addition of either two equivalent of an aryl phosphine (PPh3, P(C6H4OMe)3) or one equivalent of a bisphosphine ligands DPEPhos, XantPhos or dppf. For the first time carbodiphosphorane CDP(CH2PPh2)2 (13) could be isolated upon treating its precursor [CH(dppm)2]Cl (12) with NaNH2 in liquid NH3. A protonated and a deprotonated derivative of ligand 13 were prepared and their coordination was compared to neutral CDP ligand 13. NMR analysis and DFT calculations reveal, that the most stable tautomer of 13 does not show a CDP (or carbone) structure in its uncoordinated base form. For most of the prepared complexes, photoluminescence upon irradiation with UV light at room temperature was observed. Quantum yields (PL) were determined to 36% for dicationic [(CuPPh3)2(CDP(Py)2)](PF6)2 (4) and to 60% for neutral [(CuSPh)2(CDP(CH2PPh2)2] (16).
REVIEW | doi:10.20944/preprints202007.0489.v1
Subject: Chemistry, Inorganic & Nuclear Chemistry Keywords: High pressure X-ray crystallography; high pressure magnetometry; high pressure absorption spectroscopy; high pressure EPR; molecule-based magnets; single-molecule magnets; single-ion magnets
Online: 21 July 2020 (12:48:58 CEST)
The cornerstone of molecular magnetism is a detailed understanding of the relationship between structure and magnetic behaviour, i.e. the development of magneto-structural correlations. Traditionally, the synthetic chemist approaches this challenge by making multiple compounds that share a similar magnetic core but differ in peripheral ligation. Changes in the ligand framework induce changes in the bond angles and distances around the metal ions which are manifested in changes to magnetic susceptibility and magnetisation data. This approach requires the synthesis of series of different ligands and assumes that the chemical/electronic nature of the ligands and their coordination to the metal, the nature and number of counter ions and how they are positioned in the crystal lattice, and the molecular and crystallographic symmetry have no effect on the measured magnetic properties. In short, the assumption is that everything outwith the magnetic core is innocent, which is a huge oversimplification. The ideal scenario would be to have the same complex available in multiple structural conformations, and this is something that can be achieved through the application of external hydrostatic pressure, correlating structural changes observed through high pressure single crystal X-ray crystallography with changes observed in high pressure magnetometry, in tandem with high pressure inelastic neutron scattering (INS), high pressure electron paramagnetic resonance (EPR) spectroscopy and high pressure absorption/emission/Raman spectroscopy. In this review, which summarises our work in this area over the last 15 years, we show that the application of pressure to molecule-based magnets can (reversibly): (1) lead to changes in bond angles, distances and Jahn-Teller orientations; (2) break and form bonds; (3) induce polymerisation/depolymerisation; (4) enforce multiple phase transitions; (5) instigate piezochromism; (6) change the magnitude and sign of pairwise exchange interactions and magnetic anisotropy and (7) lead to significant increases in magnetic ordering temperatures.
ARTICLE | doi:10.20944/preprints202007.0487.v1
Subject: Chemistry, Inorganic & Nuclear Chemistry Keywords: CeO2-NPs; Musa sapientum; A549; MTT assay UV protection
Online: 21 July 2020 (12:44:32 CEST)
In recent years, the nanoparticles applications have been well recognized in various fields. It is known that nanoparticles as an active ingredient in sunscreens are widely used. Zinc oxide and titanium oxide nanoparticles are common nanoparticles utilized in sunscreens. In this study, we aimed to suggest new nanoparticles for this purpose. Cerium oxide nanoparticles (CeO2-NPs) were synthesized by using Musa sapientum fruit peel extract. Synthesized nanoparticles were identified through Raman, Powder X-ray Diffraction (PXRD), Fourier Transform Infrared spectroscopy (FT-IR), Field Energy Scanning Electron Microscopy (FESEM) and Energy-Dispersive Spectroscopy (EDX). The results showed that size of synthesized nanoparticles are in range 4-13 nm. The cytotoxic activity of synthesized nanoparticles on lung (A549) cancer cell line was performed through MTT assay. The results showed that synthesized nanoparticles are non-toxicity against A549 cell line to below 500 μg/mL of nanoparticles concentration. The Sun protection factor (SPF) was estimated ~ 40 for synthesized CeO2-NPs. So, synthesized nanoparticles can be a good option for use in the cosmetics industry.
Mon, 20 July 2020
Subject: Chemistry, Medicinal Chemistry Keywords: 3,4-dimethoxy-β-nitrostyrene derivatives; antimicrobial agent; PTP1B; molecular docking
Online: 20 July 2020 (11:31:48 CEST)
A derivative series of 3,4-dimethoxy-β-nitrostyrene were synthesized and identified including new compound 6. The effect of antimicrobial activity of 3,4-alkyloxy modification of β-nitrostyrene was investigated. A molecular docking was also performed to obtain information about their interactions with Protein Tyrosine Phosphatase 1B (PTP1B). PTP1B containing cysteine 215 and arginine 221 as essential active residues plays a key role in signaling pathways that regulate various cell functions of microorganisms, which also act as negative regulator in signaling pathways of insulin that are involved in type 2 diabetes and other metabolic diseases. Compound 5 and 6 were the most potent as fragment of PTP1B inhibitor based on molecular docking, but compound 5 was more effective against Candida albicans. These compounds interact with serine 216 and arginine 221 residues. However, further research is needed to investigate their potential medicinal use.
REVIEW | doi:10.20944/preprints202007.0459.v1
Subject: Chemistry, Electrochemistry Keywords: current-potential curve; multi-enzymatic cascades; multi-analyte detection; mass-transfer-controlled amperometric response; potentiometric coulometry
Online: 20 July 2020 (08:16:47 CEST)
Bioelectrocatalysis provides the intrinsic catalytic-functions of redox enzymes to non-specific electrode reactions and is the most important and basic concept for biosensors. This review starts by describing fundamental characteristics of bioelectrocatalytic reactions in mediated and direct electron transfer types from a theoretical viewpoint and summarizes amperometric biosensors based on multi-enzymatic cascades and for multi-analyte detection. The review also introduces prospective aspects of two new concepts of biosensors: mass-transfer-controlled (pseudo)steady-state amperometry at microelectrodes with enhanced enzymatic activity without calibration curves and potentiometric coulometry at enzyme/mediator-immobilized biosensors for absolute determination.
Sun, 19 July 2020
ARTICLE | doi:10.20944/preprints202007.0424.v1
Subject: Chemistry, Medicinal Chemistry Keywords: 4-Phenylbutyric acid; Colon-targeted drug delivery; Colitis; Prodrug; ER stress; Chemical chaperone
Online: 19 July 2020 (19:15:20 CEST)
An elevated level of endoplasmic reticulum (ER) stress is considered an aggravating factor for inflammatory bowel disease (IBD). To develop an ER stress attenuator that is effective against colitis, 4-phenylbutyric acid (4-PBA), a chemical chaperone that alleviates ER stress, was conjugated with acidic amino acids to yield a 4-PBA-glutamic acid conjugate (PBA-GA) and a 4-PBA-aspartic acid conjugate (PBA-AA). The PBA derivatives were converted to 4-PBA in the cecal contents, where the conversion was greater with PBA-GA. After oral administration of PBA-GA (oral PBA-GA), millimolar levels of PBA were accumulated in the cecum, whereas 4-PBA was not detected in the blood, indicating the targeting of PBA-GA to the large intestine. At concentrations in the cecum achievable by oral PBA-GA, 4-PBA effectively attenuated ER stress in human colon epithelial cells. In 2,4-dinitrobenzenesulfonic acid-induced colitis in rats, oral PBA-GA alleviated the damage and inflammation in the colon. Moreover, oral PBA-GA substantially reduced the elevated levels of ER stress marker proteins in the inflamed colon. Moreover, PBA-GA was as effective as the currently used anti-IBD drug, sulfasalazine. In conclusion, PBA-GA is a colon-targeted prodrug of 4-PBA and is effective against rat colitis probably through the attenuation of ER stress in the inflamed colon.
Fri, 17 July 2020
Subject: Chemistry, Physical Chemistry Keywords: polymer solution; critical micellization concentration; Zeta Potential
Online: 17 July 2020 (15:29:49 CEST)
The interaction of solution of poly (diallyldimethylammonium) chloride, PDADMAc and sodium dodecylsulfate, SDS has been studied using conductometric, densimeter and zeta potential methods. the critical micellization concentration (cmc) was determinated with conductance results and increased with the addition of PDADMAc comparing with solutions containing pure SDS. Further the degree of dissociation, and thermodynamic parameters viz. free energy of micellization, and entropy of micellization, has been evaluated. there results demonstrated that surfactant/polymer complex is governed by both electrostatic and hydrophobic interactions. The apparent molar volume, Vϕ and adiabatic compressibility, Kϕ;s have been determined for the SDS solution from density and speed sound data. the negative charge of the SDS solutions with polymer shows that these complexes probably do not contain surfactant in the form of micelles.
TECHNICAL NOTE | doi:10.20944/preprints202007.0391.v1
Online: 17 July 2020 (15:25:55 CEST)
In this scientific research, thermally stable nickel nanoparticles were synthesized and characterized. Nickel nanoparticles were synthesized using phenol –formaldehyde by chemical method followed by calcination. The polymer metal complex was confirmed by FTIR and NMR. The spherical morphology of nickel nanoparticles confirmed by SEM. The crystallographic structure is confirmed by XRD and size of cobalt nanoparticles is 24.0 nm. The TGA analysis was performed over a range of 29-600OC. The TGA thermograph predicts mass decomposition of 11%, for nickel phenol-formaldehyde nanocomposite. The decomposition rate of composites is very low 2% weight loss per 100OC increment in temperature.
Subject: Chemistry, Analytical Chemistry Keywords: mixed oxide-LDHs; manganese; wastewater; adsorption kinetics
Online: 17 July 2020 (09:14:45 CEST)
In this study, Mg-Al and Mg-Al-Ni - layered double hydroxides (LDHs) were successfully synthesized for efficient removal of Mn2+ from synthetically wastewater. LDH adsorbents (Mg-Al and Mg-Ni-Al) were prepared by co-precipitation method. The formation of the layered double hydroxide, the adsorption of manganese on both LDH (Mg-Al and Mg-Ni-Al) were observed by XRD, SEM and EDX analysis. The various parameters such as the effect of shaking time, initial Mn2+ concentration, temperature were controlled and optimized to removal of Mn2+ from synthetic wastewater. The kinetics and adsorption isotherms for Mn2+ removal from wastewater were studied in batch mode. At temperatures of 10 °C and 20 °C the adsorption equilibrium was reached after 24 h. Adsorption isotherms of Mn2+ are well fitted by Langmuir and Freundlich isotherm equation. The adsorption capacity of Mn2+ from synthetic wastewater of 80.607 mg/kg was obtained for (Mg-Al-Ni)-LDH. It is found that the adsorption kinetics is best described by the pseudo-second order model. These results prove that LDHs can be considered as a potential material for adsorption of Mn2+ from wastewater.
Thu, 16 July 2020
ARTICLE | doi:10.20944/preprints202007.0350.v1
Subject: Chemistry, Medicinal Chemistry Keywords: 3,4-DHPEA-EA; C2C12 myocytes; olive oil; antioxidant; skeletal muscle
Online: 16 July 2020 (12:56:25 CEST)
Oleuropein, glycosylated secoiridoid present in olive leaves is known to be an important antioxidant phenolic compound. We studied the antioxidant effect of low doses of oleuropein aglycone (3,4-DHPEA-EA) and oleuropein aglycone peracetylated (3,4-DHPEA-EA(P)) in murine C2C12 myocytes treated with hydrogen peroxide (H2O2). Both compounds were used at a concentration of 10 μM and were able to inhibit cell death induced by the H2O2 treatment, with 3,4-DHPEA-EA(P) being more. Under our experimental conditions, H2O2 efficiently induced the phosphorylated-active form of JNK and of its downstream target c-Jun. We demonstrated, by Western blot analysis, that 3,4-DHPEA-EA(P) was efficient in inhibiting the phospho-active form of JNK. This data suggests that the growth arrest and cell death of C2C12 proceeds via the JNK/c-Jun pathway. Moreover, we demonstrated that 3,4-DHPEA-EA(P) affects the myogenesis of C2C12 cells; because MyoD mRNA levels and the differentiation process are restored with 3,4-DHPEA-EA(P) after treatment. Overall, the results indicate that 3,4-DHPEA-EA(P) prevents ROS-mediated degenerative process in a genomic and epigenomic manner by functioning as an efficient antioxidant.
Wed, 15 July 2020
ARTICLE | doi:10.20944/preprints202007.0332.v1
Subject: Chemistry, General & Theoretical Chemistry Keywords: Car-Parrinello molecular dynamics; ab-initio molecular dynamics; sum-frequency generation spectroscopy; maximally localized Wannier orbitals
Online: 15 July 2020 (10:25:31 CEST)
In the present work, we provide an electronic structure based method for the “on-the-fly” deter- mination of vibrational sum frequency generation (v-SFG) spectra. The predictive power of this scheme is demonstrated at the air-water interface. While the instantaneous fluctuations in dipole moment are obtained using the maximally localized Wannier functions, the fluctuations in polar- izability are approximated to be proportional to the second moment of Wannier functions. The spectrum henceforth obtained captures the signatures of hydrogen bond stretching, bending, as well as low-frequency librational modes.
Tue, 14 July 2020
ARTICLE | doi:10.20944/preprints202007.0298.v1
Subject: Chemistry, Electrochemistry Keywords: Carbon nanotube; Functionalization; Heteroatoms; Electrochemically active surface; Oxygen reduction reaction; Corrosion stability; Alkaline media
Online: 14 July 2020 (11:16:31 CEST)
The influence of the type and amount of oxygen (O), nitrogen (N), and/or phosphorus (P) heteroatoms on the surface of carbon nanotube (CNT) on stability and catalytic activity in the oxygen reduction reaction (ORR) was investigated in alkaline media. It is shown that the functionalization of CNT leads to the growth of the electrochemically active surface and to an increase in the activity in ORR. At the same time, a decrease in stability is observed after the functionalization of CNT under accelerated corrosion testing in an alkaline media. These results are most significant on CNT after functionalization in HNO3 due to the formation of a large number of structural defects. However, the subsequent doping by N and / or P atoms provides a further activity increase and enhances the corrosion stability of CNT. Thus, as shown by the studies of characteristic parameters (SEAS, E1/2, corrosion stability), CNT doped with N and NP are a promising catalytic system that can be recommended for use as fuel cell cathodes. An important condition for effective doping is the synthesis of carboxyl and carbonyl oxygen containing group on the surface of CNT.
Sat, 11 July 2020
ARTICLE | doi:10.20944/preprints202007.0236.v1
Subject: Chemistry, Other Keywords: trace metals; mine drainage remediation; zinc; red media; biochar
Online: 11 July 2020 (09:36:40 CEST)
The river Teign in Devon has come under scrutiny for failing to meet Environmental Quality Standards for ecotoxic metals due to past mining operations. A disused mine known as Bridford Barytes mine, has been found to contribute a significant source of Zn, Cd and Pb to the river. Recently, studies have been focused on the remediation of such mine sites using low-cost treatment methods to help reduce metal loads to the river downstream. Red mud is a waste product from the aluminium industry, the utilization of this resource has proven an attractive low-cost treatment method for adsorbing toxic metals. Adsorption kinetics and capacity experiments reveal metal removal efficiencies of up to 70% within the first 2 hours when red mud is applied in pelletized form. Biochar is another effective adsorbent with the potential to remove >90% Zn using agricultural feedstock. Compliance of the Teign has been investigated by analysing dissolved metal concentrations and bioavailable fractions of Zn to assess if levels are of environmental concern. By applying a Real-World Application Model, this study reveals that compressed pellets and agricultural biochar offer an effective, low-cost option to reducing metal concentrations and thus improving the quality of the river Teign.
ARTICLE | doi:10.20944/preprints202007.0234.v1
Subject: Chemistry, Applied Chemistry Keywords: cannabis; THC; CBD; microwave assisted extraction; continuous flow
Online: 11 July 2020 (09:04:17 CEST)
Cannabis is a flowering plant that has long been used for medicinal, therapeutic, and recreational purposes. Cannabis contains more than 500 different compounds, including a unique class of terpeno-phenolic compounds known as cannabinoids; Δ9-tetrahydrocannabinol (THC) and cannabidiol (CBD) are the most prevalent cannabinoids and have been associated with the therapeutic and medicinal properties of the cannabis plant. In this paper, continuous flow microwave assisted extraction (MAE) is presented and compared with other methods for commercial cannabis extraction. The practical issues of each extraction method are discussed. The main advantages of MAE are: continuous-flow method which allows for higher volumes of biomass to be processed in less time than existing extraction methods, improved extraction efficiency leading to increased final product yields, improved extract consistency and quality because the process does not require stopping and restarting material flows, and ease of scale-up to industrial scale without the use of pressurised batch vessels. Moreover, due to the flexibility of changing the operation conditions, MAE eliminates additional steps required in most extraction methods, such as biomass decarboxylation, winterisation, which typically adds at least a half day to the extraction process. Another factor that sets MAE apart is the ability to achieve high extraction efficiency even at the industrial scale. Whereas the typical recovery of active compounds using supercritical CO¬2 remains around 70-80%, via MAE up to 95% of the active compounds from cannabis biomass can be recovered at the industrial scale.
REVIEW | doi:10.20944/preprints202007.0222.v1
Subject: Chemistry, Medicinal Chemistry Keywords: ROS; oxidative stress; catalytic antioxidants; superoxide dismutase; catalase; peroxidase; manganese; salen-type ligands; animal studies
Online: 11 July 2020 (03:30:41 CEST)
Manganosalen complexes are coordination compounds that possess a chelating salen-type ligand, a class of bis-Schiff bases obtained by condensation of salicylaldehyde and a diamine. They may act as catalytic antioxidants mimicking both the structure and the reactivity of the native antioxidant enzymes active site. Thus, manganosalen complexes have shown to exhibit superoxide dismutase, catalase, and glutathione peroxidase activities, and they could potentially facilitate the scavenging of excess ROS, thereby restoring the redox balance in the damaged cells and organs. Initial catalytic studies compared the potency of these compounds as antioxidants in terms of rate constants of the chemical reactivity against ROS, giving catalytic values approaching and even exceeding that of the native antioxidative enzymes. Although most of these catalytic studies lack of biological relevance, subsequent in vitro studies have confirmed the efficiency of many manganosalen complexes in oxidative stress models. These synthetic catalytic scavengers, cheaper than natural antioxidants, have accordingly attracted intensive attention for the therapy of ROS-mediated injuries. The aim of this review is to focus on in vivo studies performed on manganosalen complexes and their activity on the treatment of several pathological disorders associated with oxidative damage. This disorders, ranging from the prevention of fetal malformations to the extension of lifespan, include neurodegenerative, inflammatory and cardiovascular diseases, tissue injury, and other damages related to liver, kidney or lungs.
ARTICLE | doi:10.20944/preprints202007.0221.v1
Subject: Chemistry, Food Chemistry Keywords: hCA IX and XII; dual inhibitors; molecular modeling studies; in vitro assays
Online: 11 July 2020 (02:30:03 CEST)
The tumour-associated isoenzymes, hCA IX and hCA XII catalyze the hydration of carbon dioxide to bicarbonate and protons. These isoforms are highly overexpressed in many types of cancer, where they contribute for the acidification of the tumor environment promoting the tumor cell invasion and metastasis. In this work, in order to identify novel dual hCA IX and XII inhibitors, virtual screening techniques and biological assays were combined. A structure based virtual screening towards hCA IX and XII was performed using a database of approximately 26000 natural compounds. The best shared hits were submitted to a thermodynamic analysis and 3 promising best hits were identified and evaluated in terms of their hCA IX and XII inhibitor activity. In vitro biological assays are in line with the theoretical studies and revealed that Syringin, Lithospermic acid, and (-)- Dehydrodiconiferyl alcohol behave as good hCA IX and hCA XII dual inhibitors.
Mon, 6 July 2020
ARTICLE | doi:10.20944/preprints202007.0096.v1
Subject: Chemistry, Organic Chemistry Keywords: heterogeneous catalysis; montmorillonite; benzimidazoles
Online: 6 July 2020 (04:17:20 CEST)
The use of alternative synthetic methods, in the face of traditional processes that do not conform to the principles of Green Chemistry, represent a problem in the pharmaceutical industry. The procedures for the synthesis of benzimidazole derivatives have become a focus in synthetic organic chemistry, as they are building blocks of strong interest for the synthesis of compounds with pharmacological activity. Various benzimidazole derivatives have found very strong application in medicine and their synthesis is reported in the literature. A simple and environmental Montmorillonite K10 (MK10) catalyzed method for the synthesis of benzimidazole derivatives has been developed. The use of MK10 as heterogeneous catalysis provides various advantages in terms of yields, in the work up procedure of the reaction, selectivity and the possible recycle of catalyst without waste formation. The reactions were carried out in solvent free condition and in short reaction time using an inexpensive and environmentally friendly heterogeneous catalysis and it has been shown that the reaction process is applicable in the industrial field.
Sun, 5 July 2020
ARTICLE | doi:10.20944/preprints202007.0076.v1
Subject: Chemistry, Food Chemistry Keywords: coffee; cold brew; nitro cold brew; roasting; extraction; hygiene; risk assessment; product quality
Online: 5 July 2020 (14:53:27 CEST)
Cold brew coffee has emerged as a new trend during the last decade. However, “cold brew” is an extraction style of ground roasted coffee with water at less than body temperature (typically 8°C or room temperature) rather than a beverage per se. Cold brew extraction poses several challenges including the need of specific optimization depending on the multivariate influences of coffee variety and processing, roast degree, grinding, dosage, water composition, turbulence, brew system (drip, immersion etc.), time and temperature. While cold brew is typically characterized by a floral sweetness, over-extraction may lead to abundant acidity and bitterness. To avoid this, an extraction degree of 70% was suggested using rather shorter times (i.e. 2 h at 15°C with 80 g/L coffee with optimized medium roast profiles). Due to the lack of sterilizing temperatures during preparation, cold brew is special in the coffee sector because hygiene and food safety aspects pose specific challenges for food industry. To avoid microbiological contamination and spoilage, cold brew should be as freshly prepared as possible and shelf-life should be minimized.
Fri, 3 July 2020
ARTICLE | doi:10.20944/preprints202007.0031.v1
Subject: Chemistry, Electrochemistry Keywords: spin dependent electrochemistry; water splitting; nickel; chirality; OER
Online: 3 July 2020 (09:09:56 CEST)
Results are presented concerning the influence on the water splitting process of enantiopure tartaric acid present in bulk solution. Stainless steel and electrodeposited nickel are used as working electrode (WE) surface. The latter is obtained by electrodeposition on the two poles of a magnet. The influence and role played by the chiral compound in solution has been assessed by comparing the current values, in cyclic voltammetry (CV) experiments, recorded in the potential range at which oxygen evolution reaction (OER) occurs. In the case of tartaric acid and nickel WE a spin polarization of about 4 % is found. The use of the chiral environment (bulk solution) and ferromagnetic chiral Ni electrode allows for observing the OER at a more favourable potential: about 50 mV (i.e. a cathodic, less positive, shift of the potential at which the oxygen evolution is observed).
Tue, 30 June 2020
ARTICLE | doi:10.20944/preprints202006.0358.v1
Subject: Chemistry, Medicinal Chemistry Keywords: Enzyme inhibition; Secondary Metabolites; In-silico Analysis; Molecular docking; Drug candidates
Online: 30 June 2020 (08:11:28 CEST)
Metabolic enzymes are often targeted for drug development programs of metabolic diseases such as diabetes and its complications. Many secondary metabolites isolated from natural products have shown therapeutic action against these enzymes. However, some commercially available synthetic drugs have shown unfriendly impacts with various side effects. Thus, this research has focused on a comprehensive study of secondary metabolites showing better inhibitory activities towards metabolic enzymes such as α-amylase, α-glucosidase, aldose reductase, and lipase. Further receptor-based virtual screening was performed against the various secondary metabolites database designed in-silico. Using Gold combined with subsequent post-docking analyses, the score was obtained as methyl xestospongic ester (Gold score 65.83), 2,″4″-O-diacetylquercitrin (Gold score 65.15), kaempferol-3-O-neohesperidoside (Gold score 53.37) and isosalvianolic acid C methyl ester (Gold score 53.44) for lipase, aldol reductase, α-amylase, and α-glucosidase, respectively. Besides, vitexin and isovitexin for α-amylase; N-trans-Caffeoyl-tyramin for α-glucosidase; purpurolide F and schaftoside for lipase; acteoside and orientin for aldose reductase could be potential drugs for respective enzymes based on in-silico analyses, supported by experimental IC50 values reported. They could bind to the competitive sites of the various targets of metabolic enzymes, and finally, toxicity analysis using ProTox-II was also performed.
Sun, 28 June 2020
ARTICLE | doi:10.20944/preprints202006.0342.v1
Subject: Chemistry, Analytical Chemistry Keywords: Heavy metal; Platinum electrode; Ion beam sputtering deposition; Nanoparticle; IBSD; Ion detection
Online: 28 June 2020 (19:31:19 CEST)
An electrochemical sensing platinum nanoparticle in the tantalum electrode is provided by means of an Ion Beam Sputtering Deposition (IBSD). The electrode was made with a Pt solution, sputtered simultaneously with hydrochloric acid corrosion on tantalum substrate. In the study of heavy metal ions, for example, the platinum nanoparticle electrodes as prepared were used Square wavelength voltammetry (OSWV) Hg2+, Cu2+ and Ag2+. The porous electrodes were observed in a broader range by the Pt nanostructure electrode for heavy metal ions. Furthermore, the susceptibility to detection has been shown to be saturated as the thickness of the layer electrode exceeded 50 nm. For Hg2+ 0,003-1 M, for Cu2+ 0,005-3 M and for Ag2+ the linear detection scale is 0,009-4 M. There has also been good reusability and repeatability. In addition, a scan electron microscope (SEM) used to study platinum electrode forming process and nanostructure. This electrode will have interesting applications in sensing systems.
ARTICLE | doi:10.20944/preprints202006.0326.v1
Subject: Chemistry, Medicinal Chemistry Keywords: 2019-nCoV; 3CLpro protein; Cat's Claw; Uncaria tomentosa; Molecular Modeling
Online: 28 June 2020 (09:05:54 CEST)
COVID-19 is a novel severe acute respiratory syndrome coronavirus. Presently, there is no effective treatment for COVID-19. As part of the worldwide efforts to find efficient therapies and preventions, it has been reported the crystalline structure of the SARS-CoV-2 main protease Mpro (also called 3CLpro) bound to a synthetic inhibitor which represents a major druggable target. The druggability of Mpro could be used for discovering drugs to treat coronavirus disease 2019. It was carried out a multi-level computational study to evaluate the potential anti-viral properties of the components of the medicinal herb Uncaria tomentosa (Cat´s claw) focusing on the inhibition of Mpro. The in-silico approach starts with protein-ligand docking of 26 Cat’s claw key components followed by ligand pathway calculations, molecular dynamics simulations and MM-GBSA calculation of the free energy of binding for the best docked candidates. The structural bioinformatics approaches led to the identification of three bioactive compounds of Uncaria tomentosa (Speciophylline, Cadambine and Proanthocyanidin B2) with potential therapeutic effects by strong interaction with 3CLpro. Additionally, in silico drug-likeness indices for these components were calculated and show good predicted therapeutic profiles of these phytochemicals. Our findings suggest the potential effectiveness of Cat's claw as complementary and/or alternative medicine for COVID-19 treatment.
Sun, 14 June 2020
ARTICLE | doi:10.20944/preprints202006.0179.v1
Subject: Chemistry, Analytical Chemistry Keywords: Heavy metal; Platinum electrode; Ion beam sputtering deposition; Nanoparticle; IBSD; Ion detection
Online: 14 June 2020 (14:46:10 CEST)
Today, contamination from heavy metals in the atmosphere is a global concern. Efficient detection techniques are therefore necessary if heavy metal exposure levels in different media are to be determined. The voltammetry method for in situ detection of heavy metal ions is a very sensitive electrochemical method. This thesis explores emerging developments in electrode alteration, materials production and experimental optimization. An electrochemical sensing platinum nanoparticle in the tantalum electrode is provided by means of an Ion Beam Sputtering Deposition (IBSD). The electrode was made with a Pt solution, sputtered simultaneously with hydrochloric acid corrosion on tantalum substrate. In the study of heavy metal ions, for example, the platinum nanoparticle electrodes as prepared were used Square wavelength voltammetry (OSWV) Hg2+, Cu2+ and Ag2+. The porous electrodes were observed in a broader range by the Pt nanostructure electrode for heavy metal ions. Furthermore, the susceptibility to detection has been shown to be saturated as the thickness of the layer electrode exceeded 50 nm. For Hg2+ 0,003-1 M, for Cu2+ 0,005-3 M and for Ag2+ the linear detection scale is 0,009-4 M. There has also been good reusability and repeatability. In addition, a scan electron microscope (SEM) used to study platinum electrode forming process and nanostructure. This electrode will have interesting applications in sensing systems.
ARTICLE | doi:10.20944/preprints202006.0177.v1
Subject: Chemistry, Analytical Chemistry Keywords: Hydrochlorothiazide; Differential pulse voltammograms; Cyclic Voltammetry; Molybdenum; Modified electrode
Online: 14 June 2020 (14:40:00 CEST)
Molybdenum oxides is well-known electro-catalysts in fuel cells systems, they are usually used as anodic materials for the oxidation of low molecular weight alcohols. The utilization of Mo as catalysts in the pharmaceutical analysis is not common yet. In this study, bare glassy carbon electrodes were modified by the oxides by means of electrochemical deposition and the modified electrodes were used as catalysts for the electrochemical oxidation of hydrochlorothiazide (HCT). Well-resolved anodic peaks were reported for the analyzed pharmaceuticals when the Mo/GCE was utilized for the analysis of HCT. Analytical performance of the modified electrodes was evaluated based on the following statistical parameters; linearity ranges, correlation coefficients, limits of detection and quantitation, and recovery values. The prepared electrodes were used for the determination of the active ingredients in their pharmaceutical formulations and the reported activity was correlated to influence of the utilized pH on both structures of the used electrodes and the detected analytes.
Sun, 7 June 2020
ARTICLE | doi:10.20944/preprints202006.0108.v1
Subject: Chemistry, Organic Chemistry Keywords: Chlorella vulgaris; biodiesel; phytoremediation; molecular networking; pigments
Online: 7 June 2020 (16:36:23 CEST)
The commercial cultivation of microalgae began in the 1960s and Chlorella was one of the first target organisms. The species has long been considered a potential source of renewable energy, an alternative for phytoremediation, and more recently, as a growth and immune stimulant. However, Chlorella vulgaris, which is one of the most studied microalga, has never been comprehensively profiled chemically. In the present study, comprehensive profiling of the Chlorella vulgaris metabolome grown under normal culture conditions was carried out, employing tandem LC-MS/MS to profile the ethanolic extract and GC-MS for fatty acid analysis. The fatty acid profile of C. vulgaris was shown to be rich in omega-6, -7, -9, and -13 fatty acids, with omega-6 being the highest, representing more than sixty percent (>60%) of the total fatty acids. This is a clear indication that this species of Chlorella could serve as a good source of nutrition when incorporated in diets. The profile also showed that the main fatty acid composition was that of C16-C18 (>92%), suggesting that it might be a potential candidate for biodiesel production. LC-MS/MS analysis revealed carotenoid constituents comprising violaxanthin, neoxanthin, lutein, β-carotene, vulgaxanthin I, astaxanthin, and antheraxanthin, along with other pigments such as the chlorophylls. In addition to these, amino acids, vitamins, and simple sugars were also profiled, and through mass spectrometry-based molecular networking, 48 phospholipids were putatively identified.
Thu, 4 June 2020
ARTICLE | doi:10.20944/preprints202006.0023.v1
Subject: Chemistry, Analytical Chemistry Keywords: Nymphaea lotus L.; stamen; ultrasound-assisted extraction; macroporous resin (MPR) purification; in vitro; in cellulo; antioxidant; flavonoids
Online: 4 June 2020 (03:59:58 CEST)
Nymphaea lotus L. is the medicinal plant that has long been used as food, cosmetic and traditional medicines in Africa and Asia since the ancient time. Its flavonoids and other interesting phytochemical compounds from rhizome, leaf, and the whole flowers have been reported in the previous published researches. However, stamens, which are essential for reproductive functions, may also represent new alternative sources of potential antioxidant flavonoids as investigated in this study. The innovative green chemistry method i.e. ultrasound-assisted extraction (USAE) as well as macroporous resin (MPR) purification procedure were employed in this current research. The optimal ultrasound-assisted extraction condition is 90 % (v/v) aqEtOH with 34.65 khz ultrasonic frequency and 46 minutes of extraction time. Comparing with heat reflux extraction (HRE) conventional method, the significant gain of 1.35 total flavonoids content was obtained using optimized USAE conditions, jumping to 2.80 when this USAE associated with MPR purification. Not only in vitro cell free antioxidant activity of N. lotus stamen extracts, but also in cellulo antioxidant investigation using yeast model showed the same trend to indicate that the best antioxidant flavonoid can be found in USAE coupled with MPR purification. Moreover, the key antioxidant genes expression in yeast model such as SIR2 and SOD2 were also expressed at the highest level in yeast cell treated with the extract from USAE together with MPR purification. Consequently, it can be seen that the USAE combined with MPR purification can help to enhance the flavonoids antioxidant potential of the stamens extract from this medicinal species.
Sun, 31 May 2020
Subject: Chemistry, Food Chemistry Keywords: Nutrition system; Carbon footprint; Energy metabolism; Anthropometric; Biomedical treatment
Online: 31 May 2020 (21:01:47 CEST)
To reduce the risk factors for mortality, the paper has focused on the assessment of the socioeconomic, clinical, physical, biophysiological, and biochemical characteristics of Down's syndrome which can be affected by the type of nutrition system, toxicity, and ecological footprint. Patients were males with trisomy 21 diagnosed by karyotype test and assessed by clinical examinations. Samples were collected from different biofluids. The physicochemical analyses of the biomatrix samples were performed and these properties had compared to findings of healthy males and age-matched controls. Duraphat application was proved effective for their oral treatment and saliva was the optimum biomarker for detecting malnutrition. Patients were hypersensitive to Cu while the Mn content in blood and hair was considered an expression to the degree of epileptic condition and chronic seizure development. The ecological footprint was 5.6 gha and carbon footprint was recognised in food poverty habits. These can be reduced by eating more plant-based proteins and fibre-rich foods with low saturated fats and sodium. The findings provide an up-to-date reference for expected developmental outcomes in children with DS in terms of biophysicochemistry. The genetically sensitive intervention is affected by heredity factor and sensitivity to toxics. Down's syndrome is encouraged to live green-hipster life.
ARTICLE | doi:10.20944/preprints202005.0511.v1
Subject: Chemistry, Applied Chemistry Keywords: quantum cascade laser; remote detection; partial least squares; high explosives; artificial intelligence; machine learning
Online: 31 May 2020 (20:57:47 CEST)
A tunable quantum cascade laser (QCL) spectrometer was used to develop methods for detecting and quantifying high explosives (HE) in soil based on multivariate analysis (MVA) and artificial intelligence (AI). For quantification, mixes of 2,4-dinitrotoluene (2,4-DNT) with concentrations from 0% to 20% w/w were investigated using three types of soils: bentonite, synthetic soil, and natural soil. A Partial least squares regression model was generated for predicting 2,4-DNT concentrations. To increase its selectivity, the model was trained and evaluated using additional analytes as interferences, including other HEs such as PETN, RDX, and TNT and non-explosives such as benzoic acid and ibuprofen. For detection, mixes of different explosives in soils were used to implement two AI strategies. In the first strategy, the spectra of the samples were compared with those of soils recorded in a database to identify the most similar soils based on QCL spectroscopy. Next, a Classical Least Squares preprocessing (Pre-CLS) was applied to soils spectra selected from the database. The parameter obtained based on the sum of the weights of Pre-CLS was then used to generate a simple binary discrimination model for distinguishing between contaminated and uncontaminated soils, achieving an accuracy of 0.877. In the second AI strategy, the same parameter was added to a principal component matrix obtained from spectral data of samples and used to generate multi-classification models based on different machine learning algorithms. A Random Forest model worked best with 0.997 accuracy and allowing to distinguish between soils contaminated with DNT, TNT, or RDX and uncontaminated soils.
ARTICLE | doi:10.20944/preprints202005.0496.v1
Subject: Chemistry, Applied Chemistry Keywords: bioorthogonal chemistry; fluorescence; glycosylation; metabolic incorporation; GFP; beta-catenin
Online: 31 May 2020 (19:37:26 CEST)
Monitoring glycosylation changes within cells upon response to stimuli remains challenging because of the complexity of this large family of post-translational modifications (PTMs). We have developed an original tool enabling labeling and visualization of the cell cycle key-regulator b-catenin in its O-GlcNAcylated form based on intramolecular Förster resonance energy transfer (FRET) technology in cells. We opted for a bioorthogonal chemical reporter strategy based on the dual-labeling of b-catenin with a green fluorescent protein (GFP) for protein sequence combined with a chemically-clicked imaging probe for PTM resulting in a fast and easy to monitor qualitative FRET assay. We validated this technology by imaging the O-GlcNAcylation status of b-catenin in HeLa cells. Moreover, the changes in O-GlcNAcylation of b-catenin were varied by perturbing global cellular O-GlcNAc levels with inhibitors of O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA). Finally, we provided a flowchart demonstrating how this technology is transposable to any kind of glycosylation.
Sun, 24 May 2020
ARTICLE | doi:10.20944/preprints202005.0402.v1
Subject: Chemistry, Analytical Chemistry Keywords: electrical conductivity; volcanic tuff; cyclic voltammetry; conductivity nanoparticle; platinum electrode
Online: 24 May 2020 (19:17:53 CEST)
This paper has experimentally measured volcanic tufa electrical conductance. The calculations are carried out in accordance with the potential of cyclic voltammetry in a constant state. The cyclic voltammograms nanoelectrode platinum prepared electrochemically were examined in the range -0.2 to 1.2 V vs. AgCl [Cl-]:1.0 M in the presence and absence of volcanic tuff in the aqueous solution of 1.0 M HCl. The cyclic voltammetry studies show that the Nano platinum film suffers degradation when the potential exceeds +0.85 V, and below this potential, it is quite stable. The redox reaction of the electrode is reversible. The nanoparticle platinum synthesized at low temperature and high acid concentration exhibits higher electronic conductivities. It has been observed that, relative to area under the peak aggregate tests, the use of volcanic concrete was showing a large increase in electrical conductivity. It was shown that with cyclic voltammetry, three well-defined anode peak could be achieved at a power of 0.0, 0.4 and 0.6 V versus Ag/AgCl.
Sat, 23 May 2020
BRIEF REPORT | doi:10.20944/preprints202005.0355.v1
Subject: Chemistry, Chemical Engineering Keywords: microplastics; analysis; waste treatment; food; diet
Online: 23 May 2020 (04:58:22 CEST)
This preprint is focused in the presence of plastics and microplastics in food. We will discuss how many we eat, and how they arrive to the food, and why. We will treat many other things, such as the waste treatment in Europe and in Spain, with updated data; how much plastic waste is generated; what are microplastics and how they are analyzed, I will tell about the experience we have at the University of Alicante (UA); how they can be removed and we will estimate how many we eat over the course of a year.
Mon, 18 May 2020
ARTICLE | doi:10.20944/preprints202005.0302.v1
Subject: Chemistry, Applied Chemistry Keywords: lanthanum; multiwalled carbon nanotubes; adsorption; recovery
Online: 18 May 2020 (12:35:28 CEST)
The behaviour of oxidized and non-oxidized multiwalled carbon nanotubes in the adsorption of lanthanum(III) from aqueous solutions is described. Metal uptake is studied as a function of several variables such as the stirring speed of the system, pH of the aqueous solution and metal and nanomaterial concentrations. The experimental results are fitted to various kinetics and isotherm models, being the rate law fitted to the film diffusion and particle diffusion models, when the non-oxidized and the oxidized nanomaterials are used to remove lanthanum from the solution, respectively. Sulphuric acid solutions seem to be appropriate to recover the metal from La-loaded nanomaterials.
Thu, 7 May 2020
Online: 7 May 2020 (13:48:05 CEST)
Today, the entire globe is struggling to deal with the greatest pandemic of the century, COVID-19. With no clinically approved treatments available, we are left with no options other than following the preventive measures issued by the World Health Organization (WHO). Among many others, hand washing with soap and water has been emphasized the most because it is cost-effective and easily accessible to the general public. Various studies have reported that soaps offer unique chemical properties that can disinfect the virus as a whole. However, there is still ambiguity in the general public about whether soaps can really shield us from this highly contagious disease. In an attempt to help eliminate the ambiguity, we analyzed the mechanisms underlying the efficacy of soap and its prospect for preventing the spread of COVID-19. In this paper, we provide an overview of the history and characteristics of SARS-CoV-2 (COVID-19), the detailed mechanisms of the deactivation of viruses by soaps, and the potential effectiveness of soap in eliminating coronaviruses including SARS-CoV-2.
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