ARTICLE | doi:10.20944/preprints201808.0262.v1
Subject: Biology, Entomology Keywords: tomato pest; Tuta absoluta; bioassay; pesticide resistance; LD50; CYP450s
Online: 15 August 2018 (04:24:01 CEST)
In 2016 northern Nigeria experienced a devastating infestation by the tomato leaf miner, leading to soaring in prices of tomato across the country. Unfortunately, information on the bionomics and resistance status of this pest is lacking in northern Nigeria, hampering appropriate control measures. Here, we identified to species level, and using conventional and synergist bioassays characterised pesticides resistance profile of a field population of a tomato leaf miner from northern Nigeria. Highest resistance was obtained with λ-cyhalothrin (Type II pyrethroid) with a low mortality (18.52% at 56hr) and LD50 of 7461.474ppm. Resistance was also established toward propoxur and chlorpyrifos-methyl with average mortalities each of 56% and LD50s of 1023.51ppm and 106.351ppm, respectively. Highest susceptibility was seen with abamectin with mortality of 86% and LD50 of 0.034ppm. Pre-exposure to piperonyl butoxide significantly recovered λ–cyhalothrin susceptibility (mortality = 90% and LD50 = 0.92ppm) implicating the P450 monoxygenases in the resistance. No significant changes in mortalities were obtained on pre-exposure to diethyl maleate and triphenyl-phosphate- inhibitors of glutathione S-transferases and carboxylesterases, respectively. The finding of resistance to these agricultural pesticides will sensitize stakeholders across Nigeria to take action to manage the resistance at an early stage before it gets out of hand.
ARTICLE | doi:10.20944/preprints202109.0193.v1
Subject: Life Sciences, Microbiology Keywords: bioassay; chromatography; folkloric medicine; methicillin-resistant Staphylococcus aureus; Senna alata; spectroscopy
Online: 13 September 2021 (07:21:28 CEST)
Senna alata (Linn) Roxb. plant is widely used to manage various infections in folkloric medicine. Methicillin-resistant Staphylococcus aureus (MRSA) infection continues to be a major global public health problem. This study aims to investigate the bioactive components of S. alata leaves active against MRSA. The leaves of S. alata were sequentially extracted and fractionated using standard methods and screened for activities against MRSA. The diethyl ether active thin layer chromatography (TLC) spot was subjected to infrared (IR) and gas chromatography-mass spectroscopic (GC-MS) studies. The aqueous extract and diethyl ether fraction of S. alata leaves elicited the highest activity against the MRSA. The GC-MS analysis of the fraction produced 15 eluates; only the sub-fraction 13 was effective. The TLC analysis of the sub-fraction 13 revealed three spots; only the second spot produced activity. The GC-MS result of the spot showed six peaks. The spectral results for peak 3 match the data from the IR study suggestive of 9-octadecenoic acid methyl ester. Senna alata leaves possess bioactive compounds closely related to 9-octadecenoic acid methyl ester with potent antibacterial activity against MRSA.
ARTICLE | doi:10.20944/preprints201911.0071.v1
Subject: Chemistry, Medicinal Chemistry Keywords: NMDAR; amantadine; dansyl; fluorescent ligand; energy minima; molecular modelling; fluorescent bioassay
Online: 7 November 2019 (04:17:07 CET)
Excitotoxicity related to the dysfunction of the N-methyl-d-aspartate receptor (NMDAR) has been indicated to play an integral role in the pathophysiology of multiple disease states, including neurodegenerative disorders such as Parkinson’s disease. There is a notable gap in the market for novel NMDAR antagonists, however current methods to analyze potential antagonists rely on indirect measurements of calcium flux and hazardous radioligand binding assays. Recently, a fluorescent NMDAR ligand, N-adamantan-1-yl-dimethylamino-1-naphthalenesulfonic acid, known as AM-DAN was developed by our group. Additional studies on this ligand is necessary to evaluate its potential as a biological tool in NMDAR research. Therefore, this study was aimed at conducting structural analyses, fluorescence experiments, high-accuracy NMDAR molecular modelling and NMDAR phencyclidine (PCP) site competition binding studies using AM-DAN. Results revealed that AM-DAN has appropriate structural properties, significant fluorescent ability in various solvents and is able to bind selectively and compete for the PCP-binding site of the NMDAR. Therefore, AM-DAN holds promise as a novel fluorescent ligand to measure the affinity of prospective drugs binding at the NMDAR PCP-site and may circumvent the use of radioligands.
ARTICLE | doi:10.20944/preprints202102.0390.v1
Subject: Life Sciences, Biochemistry Keywords: Oroxylum indicum; Oroxyquinone; Traditional medicine; Bioassay Guided Fractionation; caspase-independent apoptosis; anti-metastatic
Online: 17 February 2021 (12:55:57 CET)
Leaf crude extract (aqueous) of Oroxylum indicum (L.) Kurz induces genomic DNA fragmentation, comet formation, and inhibition of cell proliferation in prostate cancer cell line, PC3 as assessed by agarose gel electrophoresis, comet assay, and MTT assay respectively. The bioactive compound was purified through bioassay-guided fractionation using preparative HPLC and MTT as-say. The brown and water-soluble compound was characterized using 1H and 13C nuclear magnetic resonance (NMR), fourier transform infrared (FT-IR) and electrospray ionization (ESI) mass spectrometry, and the compound was iden-tified as a glycosylated hydroquinone derivative, 2-[p-(2-Carboxyhydrazino)phenoxy]-6-(hydroxymethyl) tetrahy-dro-2H-pyran-3,4,5-triol (molecular formula, C13H18N2O8; molecular mass = 330). The identified phytocompound has not been reported earlier elsewhere. Therefore, the common name of the novel anticancer phytocompound isolated from oroxylum indicum in this current study is named as oroxyquinone. The half-maximal inhibitory concentration (IC50) of oroxyquinone on PC3 cells was 19.44 µg/ml (95% CI = 17.97 to 21.04). Oroxyquinone induced cell cycle arrest at S phases and inhibition of cell migration on PC3 as assessed by flow cytome-try and wound healing assay respectively. On investigating the molecular mechanism of inducing apoptosis, the results indicated that the oroxyquinone induced apoptosis through the p38 pathway and cell cycle arrest, however, not through caspase-3 and PARP pathways. The present study identifies a novel an-ticancer molecule and provides scientific evidence supporting the therapeutic potency of OI for ethnomedicinal uses.
ARTICLE | doi:10.20944/preprints202009.0094.v1
Subject: Medicine & Pharmacology, Pharmacology & Toxicology Keywords: Terminalia bentzoë; Mascarene endemic; cytotoxicity; antioxidant; cell cycle arrest; phenolics; bioassay-guided fractionation
Online: 4 September 2020 (10:28:57 CEST)
Tropical forests constitute prolific sanctuary of unique floral diversity and potential medicinal sources, however, many of them remains unexplored. Herein, seven Mascarene endemic plants leaves were extracted and evaluated for their in vitro antioxidant properties and antiproliferative effects on a panel of cancer cell lines using MTT and clonogenic cell survival assay. Flow cytometry and comet assay were used to investigate the cell cycle and DNA damaging effects, respectively. Bioassay guided-fractionation coupled with LC-Mass spectrometry (MS), gas chromatography-MS, and nuclear magnetic resonance spectroscopy analysis were used to identify the bioactive compounds. Among the seven plants tested, Terminalia bentzoë was comparatively the most potent antioxidant extract with significantly (p < 0.05) higher cytotoxic activities. T. bentzoë extract further selectively suppressed the growth of human hepatocellular carcinoma cells and significantly halted the cell cycle progression in G0/G1 phase, decreased the cells replicative potential and induced significant DNA damage. Ten phenolic compounds including punicalagin and ellagic acid were identified and likely contributed to the extract potent antioxidant and cytotoxic activities. These results established a promising basis for further in-depth investigations on the potential use of T. bentzoë as supportive therapy in cancer management.
ARTICLE | doi:10.20944/preprints201806.0136.v1
Subject: Chemistry, Organic Chemistry Keywords: Diplodia quercivora; oak; epi-epoformin; cyclohexeneoxide; etiolated wheat coleoptile bioassay; phytotoxicity; allelopathy; SAR
Online: 8 June 2018 (13:15:11 CEST)
(+)-epi-Epoformin (1), is a fungal cyclohexene epoxide isolated together with diplopimarane and sphaeropsidins A and C, a nor-ent-pimarane and two pimaranes, from the culture filtrates of Diplodia quercivora, a fungal pathogen for cork oak in Sardinia, Italy. Compound 1 possesses a plethora of biological activities including: antifungal, zootoxic and phytotoxic activity. The last activity and the peculiar structural feature of 1 suggested to carry out a structure activity relationship study, preparing eight key hemisynthetic derivatives and their phytotoxicity was assayed. The complete spectroscopic characterization and the activity in the etiolated wheat coleoptile bioassay of all the compounds is reported. Most of the compounds inhibited growth and some of them had comparable or higher activity than the natural product and the reference herbicide Logran. As regards the structure-activity relationship, the carbonyl proved to be essential for their activity of 1, as well as the conjugated double bond, while the epoxide could be altered with no significant loss.