Cytotoxic naphtho-γ-pyrones from the mangrove endophytic fungus Aspergillus tubingensis (GX1-5E)

Four new dimeric naphtho-gamma-pyrones, named rubasperone D (1), rubasperone E (2), rubasperone F (3), and its atropisomer rubasperone G (4), together with four known monomeric naphtho-gamma-pyrones, TMC 256 A1 (5), rubrofusarin B (6), fonsecin (7), and flavasperone (8), were isolated from the mangrove endophytic fungus Aspergillus tubingensis (GX1-5E) cultivated in solid rice medium. Their structures were elucidated by spectroscopic methods, including IR, 1D- and 2D-NMR, and MS. In the in vitro cytotoxicity assays, 5 displayed inhibitory activities against tumor cell lines of MCF-7, MDA-MB-435, Hep3B, Huh7, SNB19, and U87 MG with IC50 values between 19.92 and 47.98 mu m. Compounds 1, 6, and 8 also showed mild cytotoxic activity.