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., (3β,5α,6α,22E)-ergosta-7,22-diene-3,5,6-triol 6-palmitate (1), (3β,5α,6α,22E)-ergosta-7,22-diene-3,5,6-triol 6-stearate (2), (3β,5α,6α,22E)-ergosta-7,22-diene-3,5,6-triol 6-oleate (3), (3β,5α,6α,22E)-ergosta-7,22-diene-3,5,6-triol 6-linoleate (4), (3β,5α,6β,22E)-ergosta-7,22-diene-3,5,6-triol 6-palmitate (5), and (3β,5α,6β,22E)-ergosta-7,22-diene-3,5,6-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.