Novel geranylhydroquinone derived meroterpenoids from the fungus Clitocybe clavipes and their cytotoxic activity

Phenolic constituents with antibacterial activity from Eleutherine bulbosa

Eleutherine bulbosa (Mill.) Urb. is a medicinal and edible plant with various benefits for humans and animals. In this work, four new phenolic constituents (1-4), along with six known phenolic compounds (5-10) were obtained from the red bulbs of E. bulbosa. Their structures with absolute configurations were characterized by extensive spectroscopic analysis, combined with HR-ESI-MS and quantum mechanical electronic circular dichroism (ECD). Compounds 1 and 2 are novel homologous and heterodimers, respectively, featuring an unusual spiro ring system. All isolated phenolic constituents were tested for their antibacterial effects. The results revealed four phenolic compounds 1-3 and 7 showed moderate antibacterial activity against Bacillus subtilis, Staphylococcus aureus and Escherichia coli with minimum inhibitory concentration (MIC) values ranging from 15.6 to 250.0 μg/mL.

ent-Clavilactone J and Its Quinone Derivative, Meroterpenoids from the Fungus Resupinatus sp

Metabolites 1 and 2, isolated from cultures of the basidiomycete Resupinatus sp. BCC84615, collected in a tropical forest in northeastern Thailand, showed weak antibiotic activity against Bacillus subtilis and Staphylococcus aureus and cytotoxicity against cancer cell lines. Their planar structures were elucidated by high-resolution electrospray ionization mass spectrometry and NMR spectroscopy as clavilactone J, known from the basidiomycete Ampulloclitocybe clavipes, and its new 1,4-benzoquinone derivative. A detailed analysis of the ROESY correlations in 1 confirmed the recent revision of the relative configuration of clavilactone J. However, specific rotation and Cotton effects observed by electronic circular dichroism were contrary to those of the clavilactones; thus, we assigned a rare antipodal absolute configuration.

Four Meroterpenoids with Novel Aminoglycoside Moiety from the Basidiomycete Clitocybe clavipes with Cytotoxic Activity

Four new meroterpenoids, Clavilactone M-P, possessing novel aminoglycoside moiety (1-4) and a 10-membered carbocycle fused with an α,β-epoxy-γ-lactone, were isolated from Clitocybe clavipes, a basidiomycete. Their structures with absolute configurations were determined by extensive analysis of their spectroscopic data, and the ECD method. All the isolated compounds (1-4) were evaluated for their antitumor activity against three human cancer cell lines using the MTT assay. Compound 1 and 2 exhibited a significant suppression of cell viability in the Hela (IC₅₀ = 22.8 and 19.7 μM) cell line.

Brief overview of recently reported misassigned natural products and their in silico revisions enabled by DU8ML, a machine learning-augmented DFT computational NMR method

Mostly covering 2018 to 2022This Highlight article describes a personal selection of recent misassigned structures of natural products and their revision with the aid of DU8ML, a machine learning-augmented DFT computational method for fast and accurate calculations of solution NMR chemical shifts and spin-spin coupling constants.