Polyketides from Neohelicosporium griseum: structure assignment and bioactivity investigation

In the pursuit of discovering new active metabolites from helicosporous hyphomycetes, rice fermentation products of Neohelicosporium griseum were examined. Eight compounds were isolated from this saprophytic fungus, namely vertixanthone (1), diaportheone A (2), 1,3,6,8-tetrahydroxyanthraquinone (3), lecanoric acid (4), decarboxycitrinone (5), 6,8-dihydroxy-4-hydroxymethyl-3,5-dimethyl-isochromen-1-one (6), decarboxyhydroxycitrinone (7), and ergosterin (8). The 1D and 2D NMR characteristics of compound 1 in DMSO-d₆ were detailed for the first time. Antimicrobial testing indicated that compounds 1–4 exhibited moderate activity against Pseudomonas aeruginosa, with compound 3 also showing weak activity against Staphylococcus aureus. In-vitro cytotoxicity assays revealed that compounds 1, 3, and 4 displayed cytotoxic activity against HELA cell lines, with respective IC₅₀ values of 30.8, 13.7, and 14.1 µM. Compounds 1, 3, and 4 also showed significant cytotoxicity against A549 cell lines, with respective IC₅₀ values of 24.7, 7.4, and 10.3 µM.