Culpin, a novel hydroquinone antibiotic of fungal origin

Anti-inflammatory acetylenic meroterpenoids from the ascidian-derived fungus Amphichorda felina SYSU-MS7908

A combination strategy of 13C NMR and bioinformatics was established to expedite the discovery of acetylenic meroterpenoids from the ascidian-derived fungus Amphichorda felina SYSU-MS7908. This approach led to the identification of 13 acetylenic meroterpenoids (1-13) and four biogenic analogs (14-17), including five new ones named felinoids A-E (1-4 and 15). Their structures and absolute configurations were elucidated using extensive spectroscopy, ECD quantum chemical calculations, and single-crystal X-ray diffraction analysis. Compound 1 possessed a rare cyclic carbonate in natural acetylenic meroterpenoids. The plausible shikimate-terpenoid biosynthetic pathways of 1-4 were also postulated. Five of these isolates exhibited anti-inflammatory activity by inhibiting NO production in LPS-induced RAW264.7 cells (IC50 = 11.6-19.5 μM). Moreover, oxirapentyn E diacetate showed a dose-dependent inhibition of pro-inflammatory cytokines IL-6 and TNF-α. Structural modification of oxirapentyn B yielded 29 new derivatives, among which seven showed improved activity (IC50 < 3 μM) and higher selectivity index (SI > 22). The structure-activity relationship study indicated that 7, 8-epoxy, and 6-acylation were crucial for the activity. These findings may provide a powerful tool to accelerate the discovery of new fungal acetylenic meroterpenoids for future anti-inflammatory drug development.

Inducing new bioactive metabolites production from coculture of Pestalotiopsis sp. and Penicillium bialowiezense

Coculturing two or more fungi is a useful strategy to awaken the silent genes to produce structurally diverse and bioactive natural products. Through the coculture of Pestalotiopsis sp. and Penicillium bialowiezense, six new isoprenylated chromane derivatives, including two pairs of enantiomeric ones (1a/1b-2a/2b) and two optical pure ones (3-4), two new isoprenylated phenol glucoside derivatives (6-7), as well as eight known structural analogues (5 and 8-14), were obtained. The structures of these new compounds were characterized by NMR spectroscopy, single-crystal X-ray crystallography, and ECD calculation. The Δ^10,11 double bond of pestaloficin D (5) was revised to E-configurated based on the extensive spectroscopic analyses. Compounds 1a/1b and 2a/2b were the first examples of enantiomeric isoprenylated chromane derivatives, which were successfully separated by chiral HPLC. Additionally, all the isolated compounds were evaluated for the in vitro β-glucuronidase (GUS) and butyrylcholinesterase (BChE) inhibitory activities. Compounds 1a and 1b showed significant β-glucuronidase inhibitory potency with IC₅₀ values of 7.6 and 10.3 μM, respectively. Compound 14 exhibited moderate BChE inhibitory activity with an IC₅₀ value of 21.3 μM. In addition, the structure-enzyme inhibitory activity relationship of compounds 1-14 is discussed.

Bismuth compounds in medicinal chemistry

In recent years, the chemical potential of bismuth and bismuth compounds has been actively exploited. Bismuth salts are known for their low toxicity, making them potential valuable reagents for large-scale synthesis, which becomes more obvious when dealing with products such as active pharmaceutical ingredients or synthetic intermediates. Conversely, bismuth compounds have been widely used in medicine. After extensive use in the treatments of syphilis and other bacterial infections before the advent of modern antibiotics, bismuth compounds remain important for the treatment of several gastrointestinal disorders and also exhibit antimicrobial properties and cytotoxic activity, among others. This review updates relevant advances in the past few years, concerning the application of bismuth reagents and catalysts in innovative synthetic processes for the preparation of compounds of medicinal interest, as well as the preparation, biological evaluation and potential medicinal uses of bismuth compounds.

Diarylcyclopentendione metabolite obtained from a Preussia typharum isolate procured using an unconventional cultivation approach

An uncommon 2,5-diarylcyclopentenone compound, preussidone (1), and a new biphenyl compound, 1',5-dimethoxy-3,5'-dimethyl-2,3'-oxybiphenyl-1,2'-diol (4), together with two known biphenyl compounds, 5-methoxy-3,5'-dimethyl-2,3'-oxybiphenyl-1,1',2'-triol (2) and cyperin (3), were obtained from a Preussia typharum isolate that was procured using a panel of unconventional media formulations. The structures of the new compounds were established by NMR and mass spectrometry, while the absolute configuration of 1 was assigned by quantum chemical ECD and VCD calculations. The antimicrobial and DPPH radical scavenging activities of 1-4 were tested. Compounds 2 and 4 exhibited DPPH radical scavenging activities that were comparable to the positive control ascorbic acid.

Endophytic fungi found in association with Smallanthus sonchifolius (Asteraceae) as resourceful producers of cytotoxic bioactive natural products

Smallanthus sonchifolius is a traditional Andean plant which has been cultured mainly in Brazil, Japan and New Zealand due to its medicinal properties. A study of the endophytic fungi associated to the plant was carried out in order to characterize new cytotoxic agents. Thirty two fungal strains were isolated and submitted to cultivation and extraction producing 186 extracts. Of these, 12% displayed moderate to high cytotoxic activities and were considered promising anticancer compound sources. The ethyl acetate fractions of Nigrospora sphaerica and Phoma betae liquid fermentations contained the synergistic compounds 8-hydroxy-6-methoxy-3-methylisocoumarin and (22E,24R)-ergosta-4,6,8(14),22-tetraen-3-one which are potential compounds for drug discovery. Another isolated compound, pimara-7,15-dien-3-beta-ol diterpene is being characterized for the first time through a detailed spectroscopic analysis including GC/MS, homo- and hetero-nuclear correlated NMR experiments (HMQC, HMBC, COSY and NOEdiff) along with its optical rotation.

Biosynthesis and function of polyacetylenes and allied natural products

Polyacetylenic natural products are a substantial class of often unstable compounds containing a unique carbon-carbon triple bond functionality, that are intriguing for their wide variety of biochemical and ecological functions, economic potential, and surprising mode of biosynthesis. Isotopic tracer experiments between 1960 and 1990 demonstrated that the majority of these compounds are derived from fatty acid and polyketide precursors. During the past decade, research into the metabolism of polyacetylenes has swiftly advanced, driven by the cloning of the first genes responsible for polyacetylene biosynthesis in plants, moss, fungi, and actinomycetes and the initial characterization of the gene products. The current state of knowledge of the biochemistry and molecular genetics of polyacetylenic secondary metabolic pathways will be presented together with an up-to-date survey of new terrestrial and marine natural products, their known biological activities, and a discussion of their likely metabolic origins.