Cytotoxic and Cell Proliferation Activities of Isocoumarin Derivatives Isolated from <i>Phialocephala scopiformis</i> FC-1873

Phialocephala scopiformis (Ascomycota, Helotiales, Mollisiaceae) are fungi known as both saprophytes and endophytes, forming small apothecia (1 - 3 mm in diameter) on decaying wood. In this study, three novel isocoumarin derivatives (+)-phaeosphaerin A (1), (+)-phaeosphaerin B (2), and (S)-6-demethylkigelin (3) were isolated from Phialocephala scopiformis FC-1873 collected in Japan, along with two known isocoumarins, lignicol (4) and 6,8-dihydroxy-3,5-dimethyl-1H-2-benzopyran-1-one (5). The cytotoxicity of 1 and 4 were evaluated against HL-60, PANK-1, HepG2, HT-29, and T98G cell lines, as well as their effects on cell proliferation in the skin keratinocyte cell line HaCaT. These findings highlight the potential of mollisioid fungi as a source of novel bioactive compounds.