Cottoquinazoline A and cotteslosins A and B, metabolites from an Australian marine-derived strain of Aspergillus versicolor

Abstract

An Australian marine-derived isolate of Aspergillus versicolor (MST-MF495) yielded the known fungal metabolites sterigmatocystin, violaceol I, violaceol II, diorcinol, (-)-cyclopenol, and viridicatol, along with a new alkaloid, cottoquinazoline A (1), and two new cyclopentapeptides, cotteslosins A (2) and B (3). Structures for 1-3 and the known compounds were determined by spectroscopic analysis. The absolute configurations of 1-3 were addressed by chemical degradation and application of the C(3) Marfey's method. The use of "cellophane raft" high-nutrient media as a device for up-regulating secondary metabolite diversity in marine-derived fungi is discussed. The antibacterial properties displayed by A. versicolor (MST-MF495) were attributed to the phenols violaceol I, violaceol II, and diorcinol, while cotteslosins 2 and 3 were identified as weak cytotoxic agents.