Acyl α-L-Rhamnopyranosides, a Novel Family of Secondary Metabolites fromStreptomyces sp.: Isolation and Biosynthesis

Total Synthesis of Clostrienose

This paper considers the total synthesis of a cellular differentiation regulator of Clostridium acetobutylicum, clostrienose, which is a unique fatty-acid glycosyl ester consisting of clostrienoic acid, (3R,5E,8E,10E)-3-hydroxy-tetradeca-5,8,10-trienoic acid and α-d-galactofuranosyl-(1 → 2)-α-l-rhamnose. The key features of our synthesis include stereoselective construction of a skipped-triene system in clostrienoic acid and its esterification with a disaccharide residue. The partially protected clostrienoic acid employed for the coupling also served for the preparation of l-rhamnosyl clostrienoate, thus leading to confirmation of the proposed structure unambiguously.

Cytotoxic constituents from Isotrema tadungense

In our search for cytotoxic constituents from Vietnamese plants, the methanolic extract of Isotrema tadungense was found to exhibit significant cytotoxic effect. Subsequent phytochemical investigation of ethyl acetate fractions of this plant led to isolation of 11 compounds including one new arylbenzofuran rhamnoside namely aristolochiaside (1), two aristololactams (2 and 3), three lignanamides (4-6) and five phenolic amides (7-11). Their structures were elucidated by 1 D and 2 D NMR and HR-QTOF-MS experiments. Among the isolated compounds, aristolochiaside (1), aristolactam AIIIa (2) and N-trans-sinapoyltyramine (10) exhibited strong and selective cytotoxicity on the HeLa human cancer cell line with IC₅₀ values of 7.59 ± 1.03, 8.51 ± 1.73 and 9.77 ± 1.25 μM, respectively.[Formula: see text].

Phallusialides A-E, Pyrrole-Derived Alkaloids Discovered from a Marine-Derived Micromonospora sp. Bacterium Using MS-Based Metabolomics Approaches

Integrating MS-based metabolomics approaches, LC-MS-PCA and molecular networking enabled the targeted isolation of five new pyrrole-derived alkaloids, phallusialides A-E (1-5), from a marine-derived Micromonospora sp. bacterium. The structures of 1-5 were elucidated by analysis of their HRMS, MS/MS, and NMR spectroscopic data. The absolute configuration of phallusialide A (1) was determined on the basis of comparisons of experimental and theoretically calculated ECD spectra. Compounds 1 and 2 exhibited antibacterial activity against methicillin resistant S. aureus (MRSA) and E. coli, with MIC values of 32 and 64 μg/mL, respectively, whereas 3-5 showed no antibacterial activity even at 256 μg/mL, yielding important SAR insights for this class of compounds.

New Bromopyrrole Alkaloids from the Marine Sponges Axinella Damicornis and Stylissa Flabelliformis

Investigation of the tropical sponges Axinella damicornis and Stylissa flabelliformis, family Axinillidae, afforded five new bromopyrrole alkaloids (1–5) and thirteen known compounds (6–18). Semi synthesis of 5 was carried out in order to confirm its structure. The structures of the isolated compounds were elucidated using 1D- and 2D-NMR spectroscopy and mass spectrometry. The cytotoxicity, antimicrobial and protein-kinase inhibition activities were tested for the isolated compounds.

Complete Genome Sequence of Streptomyces sp. TN58, a Producer of Acyl Alpha-l-Rhamnopyranosides

Streptomyces sp. TN58, isolated from a Tunisian soil sample, produces several natural products, including acyl alpha-l-rhamnopyranosides. It possesses a 7.6-Mb linear chromosome. This is, to our knowledge, the first genome sequence of a microorganism known to produce acyl alpha-l-rhamnopyranosides, and it will be helpful to study the biosynthesis of these specialized metabolites.

A comprehensive review of glycosylated bacterial natural products

A systematic analysis of all naturally-occurring glycosylated bacterial secondary metabolites reported in the scientific literature up through early 2013 is presented. This comprehensive analysis of 15 940 bacterial natural products revealed 3426 glycosides containing 344 distinct appended carbohydrates and highlights a range of unique opportunities for future biosynthetic study and glycodiversification efforts.

Replication of biosynthetic reactions enables efficient synthesis of A-factor, a γ-butyrolactone autoinducer from Streptomyces griseus

We report a concise synthesis of A-factor, the prototypical γ-butyrolactone signalling compound of Streptomyces bacteria. In analogy to enzymatic reactions in A-factor biosynthesis, our synthesis features a tandem esterification-Knoevenagel condensation yielding a 2-acyl butenolide and a surprising, chemoselective conjugate reduction of this α,β-unsaturated carbonyl compound using sodium cyanoborohydride.

A butenolide intermediate in methylenomycin furan biosynthesis is implied by incorporation of stereospecifically 13C-labelled glycerols

The label from [3-(13)C]-L-glycerol is incorporated into the hydroxymethyl group of methylenomycin furans suggesting a butenolide intermediate in their biosynthesis.

Five naturally bioactive molecules including two rhamnopyranoside derivatives isolated from the Streptomyces sp. strain TN58

Extraction of 25 L fermentation broth of the newly isolated Streptomyces sp. strain TN58 and various separation and purification steps led to the isolation of five bioactive metabolites, namely brevianamide F (C1), reported from a streptomycete for the first time, N(beta)-acetyltryptamine (C2), thiazolidomycin (C3), and two rhamnopyranosides (C4 and C5). These two rhamnopyranosides were produced directly, without precursor addition. The chemical structure of these five active compounds was established on the basis of (1)H, (13)C/APT and 2D NMR spectra, ESI and EI-MS data, and by comparison with data from the literature. According to the biological studies, we show in this work that the compounds C1, C2, C4 and C5 possess antimicrobial activities.

2-Alkyl-4-hydroxymethylfuran-3-carboxylic acids, antibiotic production inducers discovered by Streptomyces coelicolor genome mining

All of the genetic elements necessary for the production of the antibiotic methylenomycin (Mm) and its regulation are contained within the 22-kb mmy-mmf gene cluster, which is located on the 356-kb linear plasmid SCP1 of Streptomyces coelicolor A3(2). A putative operon of 3 genes within this gene cluster, mmfLHP, was proposed to direct the biosynthesis of an A-factor-like signaling molecule, which could play a role in the regulation of Mm biosynthesis. The mmfLHP operon was expressed under the control of its native promoter in S. coelicolor M512, a host lacking the SCP1 plasmid, and the ability to produce prodiginine and actinorhodin antibiotics. Comparative metabolic profiling led to the identification and structure elucidation of a family of 5 new 2-alkyl-4-hydroxymethylfuran-3-carboxylic acids (AHFCAs), collectively termed Mm furans (MMFs), as the products of the mmfLHP genes. MMFs specifically induce the production of the Mm antibiotics in S. coelicolor. Comparative genomics analyses and searches of the natural product chemistry literature indicated that other streptomycetes may produce AHFCAs, suggesting that they could form a general class of antibiotic biosynthesis inducers in Streptomyces species, with analogous functions to the better known gamma-butyrolactone regulatory molecules.

Plasticity in gilvocarcin-type C-glycoside pathways: discovery and antitumoral evaluation of polycarcin V from Streptomyces polyformus

Gilvocarcin-type polyketide glycosides represent some of the most powerful antitumor therapeutics. Bioactivity-guided fractionation of a culture extract of Streptomyces polyformus sp. nov. (YIM 33176) yielded the known gilvocarcin V (2) and a novel related compound, polycarcin V (1). Structure elucidation by NMR and chemical derivatization revealed that the congener (1) features a C-glycosidically linked alpha-L-rhamnopyranosyl moiety in lieu of the D-fucofuranose. The concomitant production of two distinct furanosyl and pyranosyl C-glycosides that share the same aglycone is unprecedented in bacteria. A conversion of both isoforms via a quinone methide intermediate can be ruled out, thus pointing to two individual C-glycosylation pathways. Cytotoxicity profiling of polycarcin V in a panel of 37 tumor cell lines indicated significant antitumoral activity with a pronounced selectivity for non-small-cell lung cancer, breast cancer and melanoma cells. As the antiproliferative fingerprint is identical to that of actinomycin D, the known DNA interaction of gilvocarcins was established as a general principle of antitumorigenic activity.