Bioactive Polyketide-Terpenoid Hybrids from a Soil-Derived Fungus Bipolaris zeicola

Nathmorinones A and B, two naphthyl cyclothiomorphone from Amycolatopsis sp. YINM00005

Atypical actinomycetes have long been esteemed as a precious microbial resource, renowned for their capability to produce an extensive array of bioactive natural products. Two polycyclic naphthyl cyclothiomorphone, nathmorinones A (1) and B (2), were isolated from Amycolatopsis sp. YINM00005 associated with Peperomia dindygulensis Miq. Their structures, featuring a tricyclic framework with a naphthalene ring and a thiomorphine scaffold, were elucidated through extensive analysis of NMR spectra, HRESIMS data, and further confirmed by single-crystal X-ray diffraction experiments. Compound 2 exhibited moderate cytotoxic activities against SMMC-7721 and SW480 with IC50 values of 13.65 ± 0.30 and 17.82 ± 0.30 μM, respectively. Hypothetical biosynthetic pathways for 1 and 2 were proposed.

Maydisens, Sesterterpenoids with Anti-MDR Activity from Bipolaris maydis

Fourteen previously undescribed sesterterpenoids (1-14) were isolated from Bipolaris maydis. Their structures with absolute configurations were elucidated by NMR, HRESIMS, DP4+ calculations, ECD calculations, single-crystal X-ray diffraction analyses, and the modified Mosher's method. Compounds 1-5 possess an uncommon 5/11 bicyclic ring system identified from B. maydis for the first time. Compounds 6-14 have a 5/8/5 tricyclic ring system, and these compounds both possess carbonyl groups in ring A. Compound 10 showed significant reversal of paclitaxel resistance in cancer cells.

Recent Updates on the Antimicrobial Compounds from Marine-Derived Penicillium fungi

In this review, 72 compounds isolated from marine-derived Penicillium fungi and their antimicrobial activities are reviewed from 2020 to 2023. According to their structures, these compounds can be divided into terpenoids, polyketides, alkaloids and other structural compounds, among which terpenoids and polyketides are relatively large in number. Some compounds have powerful inhibitory effects against different pathogenic bacteria and fungi. This review aims to provide more useful information and enlightenment for further efficient utilization of Penicillium spp. and their secondary metabolites.

Ten undescribed eremophilane and guaiane sesquiterpenes from Penicillium roqueforti

Nine undescribed eremophilane sesquiterpenes, one undescribed guaiane sesquiterpene, along with ten known analogues were isolated and identified from fungus Penicillium roqueforti, which was separated from the root soil of Hypericum beanii N. Robson collected from the Shennongjia Forestry District, Hubei Province. Their structures were elucidated on the basis of various spectroscopic analyses, mainly including NMR and HRESIMS data, ¹³C NMR calculation with DP4+ probability analyses, ECD calculations, and single-crystal X-ray diffraction experiments. Furthermore, all twenty compounds were evaluated for the in vitro cytotoxic activities against seven human tumor cell lines, and the result suggested that 14-hydroxymethylene-1(10)-ene-epi-guaidiol A exhibited considerable cytotoxic activity against the Farage (IC₅₀ < 10 μM, 48 h), SU-DHL-2, and HL-60 cells. Further mechanism study demonstrated that 14-hydroxymethylene-1(10)-ene-epi-guaidiol A could significantly promote apoptosis by inhibiting tumor cell respiration and decreasing intracellular ROS levels, thereby inducing S-phase blockade in tumor cells.

Identification of meroterpenoids from Bipolaris victoriae S27 and their potential activity against tumor metastasis and inhibition of the NF-κB signaling pathway

Three undescribed meroterpenoids, named bipolacochlioquinones A-C, together with seven known compounds, were isolated from the plant endophytic fungus Bipolaris victoriae S27 derived from the fresh stems of Rubia podantha Diels. Their structures were mainly determined by extensive spectroscopic analysis. The relative configurations of bipolacochlioquinones A-C were assigned using the ROESY spectrum, comparison of their spectral data with that reported in the literatures, and NMR calculations. Moreover, their complete absolute configurations were further established by electronic circular dichroism calculations using density functional theory. Among them, bipolacochlioquinone A is found to represent the first example of previously undescribed 6/6/6/6/6 pentacyclic dioxane-containing cochlioquinones, and bipolacochlioquinone B possesses a rare 6/6/6/6/5 pentacyclic system bearing a tetrahydrofuran ring fused to a polyketide and a sesquiterpenoid subunit. All compounds were evaluated for their inhibitory effects on tumor growth, metastasis, and the NF-κB signaling pathway. Among them, bipolacochlioquinone C and cochlioquinone A show the most potent cytotoxicities and NF-κB inhibitory activities. The effects of bipolacochlioquinone C and cochlioquinone A on the expression of NF-κB-associated proteins were also evaluated using western blotting. These results indicate that bipolacochlioquinone C and cochlioquinone A can inhibit the growth and metastasis of HCT116 and MDA-MB-231 cells by suppressing the NF-κB signaling pathway.

Drimane sesquiterpenoids from a wetland soil-derived fungus Aspergillus calidoustus TJ403-EL05

Soil-derived fungi represent an insufficiently tapped reservoir for discovering new and bioactive natural products (NPs), and despite an ever-increasing number of unknown NPs have been discovered over the past few decades, much of the hidden biosynthetic potential is still in an urgent need to be disclosed. In this research, a chemical investigation was performed on a wetland soil-derived fungus Aspergillus calidoustus TJ403-EL05, leading to the isolation of a total of fourteen drimane sesquiterpenoids (1-14), incorporating three new ones, namely ustusols F-H (1-3). Their structures, comprising absolute configurations, were completely authenticated by widespread spectroscopic data, quantum chemical ¹³C NMR and ECD calculations, and X-ray crystallography experiments. Compound 14 exhibited moderate anti-inflammatory activity by inhibiting the LPS-induced NO release (IC₅₀ = 25.6 μM).

Bipolaquinones A-J, Immunosuppressive Meroterpenoids from a Soil-Derived Bipolaris zeicola

Ten new meroterpenoids, bipolaquinones A-J (1-10), and one known congener, isocochlioquinone F (11), were isolated and identified from the fermented rice cultures of a soil-derived fungus, Bipolaris zeicola. The planar structures of 1-10 were elucidated based on extensive spectroscopic analyses (including HRESIMS and 1D and 2D NMR data), and their absolute configurations were determined by single-crystal X-ray diffraction analyses, comparison of experimental electronic circular dichroism (ECD) data, ECD calculations, and hydrolysis reaction. The immunosuppressive activity assay revealed that compounds 2, 3, and 7-10 showed significant inhibitory activity against concanavalin A (ConA)-induced T lymphocyte proliferation with IC₅₀ values ranging from 4.1 to 9.4 μM, which furnished potential lead molecules for the design and development of new immunosuppressants for treating autoimmune-associated diseases.

Hot off the press

A personal selection of 32 recent papers is presented covering various aspects of current developments in bioorganic chemistry and novel natural products such as chlorahupetone A from Chloranthus henryi var. hupehensis.