Aspergillamides A and B:: Modified cytotoxic tripeptides produced by a marine fungus of the genus Aspergillus.

Two isomeric linear peptides, aspergillamides A and B (1, 2), were isolated from the mycelium of a cultured marine fungus of the genus Aspergillus. The producing strain (designated CNC-120), was obtained from a saline lake sediment sample collected from Acklins Island. the Bahamas. The structures of the new peptides were elucidated using comprehensive 2D NMR methods. At 25 degrees C, in both acetone and dimethylsulfoxide, aspergillamide A exists as a 1:1 mixture of trans- and cis-amide rotational isomers (1a and 1b). Under identical conditions, aspergillamide B is predominantly in the cis-amide form. The absolute stereochemistries of the amino acids in aspergillamide A were assigned as L by hydrolysis and comparison with commercial standards. Aspergillamide A showed modest irt virro cytotoxicity [IC50 = 16 mu g/ml] toward the human colon carcinoma cell line HCT-116. (C) 1998 Elsevier Science Ltd. All rights reserved.