Cytotoxic Heptaketides from the Endolichenic Fungus Ulospora bilgramii.

Eleven new metabolites including nine heptaketides, ulosporin A-G (1a-7b), one diphenyl compound, ulophenol (8), and one spirobisnaphthalene, palmarumycin P5 (9), were isolated from the endolichenic fungus Ulospora bilgramii, which inhabits the lichen Umbilicaria sp. The structures of these compounds were elucidated based on comprehensive analysis of their spectroscopic, electronic circular dichroism (ECD), and single-crystal X-ray diffraction data. Ulosporin G (7) inhibited the growth of the human cancer cell lines A549, MCF-7, and KB with IC50 values of 1.3, 1.3, and 3.0 μM, respectively. Additionally, it induced A549 cell apoptosis through G0/G1 cell cycle arrest caused by DNA damage.