Panunoids A – D, four new prenylhydroquinone derivatives isolated from the fungus Panus rudis

A chemical constituent study on the fermented rice substrate of basidiomycetous fungus Panus rudis led to the isolation of four previously undescribed prenylhydroquinone derivatives compounds (1-4) and eight known compounds (5-12). Among them, compound 3 featured a rare benzothiazole derivative with hydroxy substituted 3-methyl-1-butenyl substitution on the benzene ring, and the absolute configurations of 7 and 12 were elucidated as unreported ones. Their structures were identified by the interpretation of 1D and 2D NMR spectroscopy, HRESIMS data, X-ray single-crystal diffraction, and comparison of calculated and experimental ECD spectra. The plausible biosynthetic pathways for 1-7 are proposed. Cytotoxicity evaluation was conducted on 1 and 3-12 against two cancer cell lines (A-549 and HepG2). The results demonstrated that 1, 3-6, 8, 9, and 12 exhibited weak cytotoxicity against both two cell lines. Among them, 8 and 12 showed dose-dependent inhibitory effects, and their IC₅₀ values at 72 h were obtained.