Tropolactones A-D, four new meroterpenoids from a marine-derived fungus of the genus Aspergillus

Four cytotoxic meroterpenoids, tropolactones A–D, were isolated from the whole broth extract of a marine-derived fungus of the genus Aspergillus. The structures of the meroterpenoids were established through a variety of two-dimensional NMR techniques. The absolute configuration of tropolactone A was determined using the modified Mosher method. Tropolactones A–C contain an interesting substituted 2,4,6-cycloheptatriene (tropone) ring, which presumably arises through an oxidative ring expansion from tropolactone D. Tropolactones A, B and C showed in vitro cytotoxicity against human colon carcinoma (HCT-116) with IC50 values of 13.2, 10.9 and 13.9 μg/mL.We appreciate the financial support provided by the NIH, National Cancer Institute under grant CA44848. M. Cueto acknowledges a postdoctoral fellowship from the Ministerio de Educacion of Spain