Unusual lipids in the Caribbean sponges Amphimedon viridis and Desmapsamma anchorata.

The phospholipid fatty acid composition of the Caribbean sponge Amphimedon viridis was studied, revealing the presence of the previously unreported substances 5,13-nonadecadienoic acid, 4-nonadecenoic acid, and 15-heneicosenoic acid. In A. viridis the very long-chain 5,9,23-nonacosatrienoic acid and 5,9,23-tricosatrienoic acid predominated in the mixture. The fatty acid composition of the sponge Desmapsamma anchorata was revised and 62 phospholipid fatty acids were characterized. The rare 8,13-octadecadienoic acid and 18-tetracosenoic acid were also characterized in the mixture. The two possible stereochemical isomers of 7-methyl-6-hexadecenoic acid, i.e., 7-methyl-6(Z)-hexadecenoic acid and the 7-methyl-6(E)-hexadecenoic acid were identified in both sponges, but D. anchorata had larger amounts. This is the first time that both stereoisomers have been identified in a sponge. The previously reported 7-methyl-8-hexadecenoic acid was not found in D. anchorata. Unprecedented aldehydes, comprising 15-and 17-docosenal, were also identified in the sponges.