ANTIFOULING POLYHYDROXYSTEROLS ISOLATED FROM A PALAUAN OCTOCORAL OF SINULARIA SP

In our continuing search for effective antifoulants from marine invert ebrates which can be used as substitutes for effective but highly toxi c agents such as organotin compounds, we found that the lipophilic fra ction from the extract of a Palauan octocoral of Sinularia sp. inhibit ed settlement of the blue mussel Mytilus edulis. Bioassay-guided isola tion afforded five polyhydroxylated sterols with or without a monoacet yl functional group such as 6 beta-acetoxy-24-methylenecholestane-3 be ta,5 alpha-diol. The inhibitory activity of one of these compounds aga inst the settlement of the blue mussel was found to be 34% of that of CuSO4, a standard antifouling agent. The activity of all five compound s was approximately 2 to 5 times stronger than that of cholesterol, be ta-cholestanol and beta-sitosterol, suggesting the importance of the h ydroxyl and/or acetoxyl groups for antifouling activity.