ARTICLE | doi:10.20944/preprints201807.0549.v1
Subject: Chemistry, Organic Chemistry Keywords: Smenospongia aurea, -pyrone, polypropionate, marine sponges, secondary metabolites, signaling molecules.
Online: 27 July 2018 (17:00:51 CEST)
The organic extract of the Caribbean sponge Smenospongia aurea has been shown to contain an array of novel chlorinated secondary metabolites derived from a mixed PKS-NRPS biogenetic route, such as the smenamides. Here we report the presence of a biogenetically different compound, smenopyrone (1), a polypropionate containing two -pyrone rings. The structure of smenopyrone, including its relative and absolute stereochemistry, was determined by spectroscopic analysis (NMR, MS, ECD) supported by comparison with model compounds from the literature. Pyrone polypropionates are unprecedented in marine sponges, but are commonly found in marine mollusks, where their biosynthesis by symbiotic bacteria has been hypothesized and at least in one case demonstrated. As pyrones have recently been recognized as bacterial signaling molecules, we speculate that smenopyrone could mediate inter-kingdom chemical communication between S. aurea and its symbiotic bacteria.
ARTICLE | doi:10.20944/preprints201805.0443.v1
Subject: Chemistry, Organic Chemistry Keywords: smenamides; marine natural products; peptide/polyketide molecules; synthetic analogues; functional-analogues; antiproliferative activity; MM cell line
Online: 30 May 2018 (09:00:58 CEST)
Smenamides are an intriguing class of peptide/polyketide molecules of marine origin showing antiproliferative activity against lung cancer Calu-1 cells at nanomolar concentrations through a clear pro-apoptotic mechanism. To probe the role of the activity-determining structural features, the 16-epi-analogue of smenamide A and eight simplified analogues in the 16-epi series were prepared using a flexible synthetic route. The synthetic analogues were tested on multiple myeloma (MM) cell lines showing that the configuration at C-16 slightly affects the activity, since the 16-epi-derivative is still active at nanomolar concentrations. Interestingly, it was found that the truncated compound 8, mainly composed of the pyrrolinone terminus, was not active while compound 17, essentially lacking the pyrrolinone moiety, was 1000-fold less active than the intact substance and was the most active among all the synthesized compounds.
ARTICLE | doi:10.20944/preprints201910.0091.v1
Subject: Chemistry, Organic Chemistry Keywords: smenospongia aurea; marine natural products; structure elucidation; anti-tumor lead molecules; smenamides; solid tumor cell lines; conformational analysis
Online: 8 October 2019 (11:08:05 CEST)
Caribbean sponges of the genus Smenospongia are a prolific source of chlorinated secondary metabolites. The use of molecular networking as a powerful dereplication tool revealed the presence in the metabolome of S. aurea of two new members of the smenamide family, namely smenamide F (1) and G (2). The structure of smenamide F (1) and G (2) was determined by spectroscopic analysis (NMR, MS, ECD). The relative and the absolute configuration at C-13, C-15, and C-16 was determined on the basis of the conformational rigidity of a 1,3-disubstituted alkyl chain system (i.e. the C-12/C-18 segment of compound 1). Smenamide F (1) and G (2) were shown to exert a selective moderate antiproliferative activity against cancer cell lines MCF-7 and MDA-MB-231, while being inactive against MG-63.
REVIEW | doi:10.20944/preprints202110.0354.v1
Subject: Chemistry, Organic Chemistry Keywords: Phorbas; marine sponges; marine natural products (MNPs); bioactivity,; cytotoxic metabolites; antimicrobial and anti-inflammatory activities; sesterterpene
Online: 25 October 2021 (13:16:55 CEST)
Porifera, commonly referred to as marine sponges, have stood out as major producers of marine natural products (MNPs). Sponges of the genus Phorbas have attracted much attention along years. They are widespread in all continents, and several structurally unique compounds have been identified from species of this genus. Terpenes, mainly sesterterpenoids, represent the great majority of secondary metabolites isolated from Phorbas species, even though several alkaloids and steroids have also been reported. Many of these compounds have shown a variety of biological activities. Particularly, Phorbas sponges have been demonstrated to be a source of cytotoxic metabolites. In addition, MNPs exhibiting cytostatic, antimicrobial and anti-inflammatory activities, have been isolated and structurally characterized. This work brings an overview of Phorbas secondary metabolites reported since the first study published in 1993 until 2020, and their biological activities.
ARTICLE | doi:10.20944/preprints202102.0397.v1
Subject: Chemistry, Analytical Chemistry Keywords: pyrazolopyrimidinone; hydrazide-hydrazone; antitumor lead compound; cytotoxic activity; antiproliferative activity; molecular docking; epidermal growth factor receptor; G-quadruplex DNA; KRAS; circular dichroism
Online: 17 February 2021 (14:05:44 CET)
Chemotherapy represents the most applied approach to cancer treatment. Owing to the frequent onset of chemoresistance and tumor relapses, there is an urgent need to discover novel and more effective anticancer drugs. In search for therapeutic alternatives to treat the cancer disease, a se-ries of hybrid pyrazolo[3,4-d]pyrimidin-4(5H)-ones tethered with hydrazide-hydrazones, 5a-h, was synthesized from condensation reaction of pyrazolopyrimidinone-hydrazide 4 with a series of arylaldehydes in EtOH, in acid catalysis. In vitro assessment of antiproliferative effects against MCF-7 breast cancer cells, unveiled that 5a, 5e, 5g, and 5h were the most effective compounds of the series and exerted their cytotoxic activity through apoptosis induction and G0/G1 phase cell-cycle arrest. To explore their mechanism at a molecular level, 5a, 5e, 5g, and 5h were evalu-ated for their binding interactions with two well-known anticancer targets, namely the epider-mal growth factor receptor (EGFR) and the G-quadruplex DNA structures. Molecular docking simulations highlighted high binding affinity of 5a, 5e, 5g, and 5h towards EGFR. CD experi-ments suggested 5a as a stabilizer agent of the G-quadruplex from the KRAS oncogene promot-er. In the light of these findings, we propose the pyrazolo-pyrimidinone scaffold bearing a hy-drazide-hydrazone moiety as a lead skeleton for designing novel anticancer compounds.
ARTICLE | doi:10.20944/preprints201912.0184.v1
Subject: Chemistry, Medicinal Chemistry Keywords: sponge; quorum sensing; quorum sensing inhibition; N-acyl homoserine lactone; Sarcotragus spinosulus; 3-Br-N-methyltyramine; 5,6-dibromo-N,N-dimethyltryptamine
Online: 13 December 2019 (12:12:54 CET)
Marine sponges, a well documented prolific source of natural products, harbors numerous microbial communities believed to possess N-acyl homoserine lactones (AHLs) mediated Quorum sensing (QS) as one of the mechanisms of interaction. Bacteria and eukaryotic organisms are known to produce molecules that can interfere with QS signaling, thus affecting microbial genetic regulation and function. In the present study, we established the potential for production of both QS signal molecules as well as QS interfering molecules (QSI) in the same sponge species Sarcotragus spinosulus. A total of eighteen saturated acyl chain AHLs were identified along with six putative unsaturated acyl chain AHLs. Bioassay guided purification led to the isolation of two brominated metabolites with QS-interfering activity. The structures of these compounds were elucidated by comparative spectral analysis of 1HNMR and HR-MS data and was identified as 3-Br-N-methyltyramine (1) and 5,6-dibromo-N,N-dimethyltryptamine (2). The QSI activity of compounds 1 and 2 were evaluated using reporter gene assays for long- and short-chain signals (E. coli pSB1075 and E. coli pSB401) and was confirmed by measuring dose dependent inhibition of proteolytic activity and pyocyanin production in P. aeruginosa PAO1. The obtained results showed the co-existence of QS and QSI in S. spinosulus, a complex network which may mediate the orchestrated function of the microbiome within the sponge holobiont.
ARTICLE | doi:10.20944/preprints201912.0399.v1
Subject: Life Sciences, Microbiology Keywords: natural product; actinobacteria; quorum sensing inhibition (QSI); biosynthetic gene clusters (BGCs); global natural product social networking (GNPS); cyclic dipeptides (2,5-diketopiperazines, DKPs); LC-HRMS
Online: 31 December 2019 (02:59:59 CET)
Streptomyces, being one of the most promising genera due to its ability to synthesize a variety of bioactive secondary metabolites of pharmaceutical interest, here studied in relation to its genomic and metabolomic potential. Coinciding with the increase in sequenced data, mining of bacterial genomes for biosynthetic gene clusters (BGCs) has become a routine component of natural product discovery. Herein, we describe the isolation and characterization of a Streptomyces tendae VITAKN with quorum sensing inhibitory activity (QSI) that was isolated from southern coastal parts of India. The nearly complete genome consists of 8,621,231bp with a GC content of 72.2%. Utilizing the BiG-SCAPE-CORASON platform, a sequence similarity network predicted from this strain was evaluated through sequence similarity analysis with the MIBiG database and existing 3,365 BGCs predicted by antiSMASH analysis of publicly available complete Streptomyces genomes. Crude extract analyzed on LC-HRMS/MS and Global Natural Product Social Molecular Networking (GNPS) online workflow using dereplication resulted in the identification of cyclic dipeptides (2,5-diketopiperazines, DKPs) in the extract, which are known to possess QSI activity. Our results highlight the potential use of genomic mining coupled with LC-HRMS/MS and bionformatic tools (GNPS) as a potent approach for metabolome studies in discovering novel QSI lead compounds. This study also provides the biosynthetic diversity of these BGCs and an assessment of the predicted chemical space yet to be discovered.
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.