New steryl esters of fatty acids from the mangrove fungus Aspergillus awamori

The polyhydroxylated ergostane-type sterol 9, its derivatives 10-15, and the fatty acid esters 1-8 were isolated from a fungus strain which was collected from mangrove areas at Wenchang, Hainan Province, P. R. China, exhibited potent cytotoxic activity. and was identified as Aspergillus awamori. The structures of 1 - 15 were elucidated by spectroscopic and chemical methods. Among them, the six steryl esters 1-6 of fatty acids were new compounds, i.e., (3 beta,5 alpha,6 alpha,22E)-ergosta-7,22-diene-3,5,6-triol 6-palmitate (1). (3 alpha,5 alpha,6 alpha,22E)-ergosta-7,22-diene-3,5,6-triol 6-stearate (2), (3 beta,5 alpha,6 beta,22E)-ergosta-7,22diene-3.5,6-triol 6-oleate (3), (3 beta,5 alpha,6 alpha,22E)-ergosta-7,22-diene-3,5,6-ti-iol 6-linoleate (4), (3 beta,5 alpha.6 beta.22E)-ergosta-7,22-diene-3,5,6-triol 6-palmitate (5), and (3 beta,5 alpha,6 beta,22E)-ergosta-7,22-diene3.5.6-triol 6-stearate (6). The related known fatty acids stearic acid (=octadecanoic acid) and palmitic acid (- octadecanoic acid) were also obtained. A speculative biogenetic relationship of the metabolites is proposed. The known polyhydroxylated sterols and derivatives showed cytotoxic activities, in agreement with earlier reports. The cytotoxic activities against B16 and SMMC-7721 cell lines of the new steryl esters 1-6 by the MTT method were weak.