Fatty Acids from a Glass Sponge Aulosaccus sp. Occurrence of New Cyclopropane-Containing and Methyl-Branched Acids

In order to identify new structures, the free fatty acids from an extract of a glass sponge Aulosaccus sp. (from the north-west Pacific) belonging to one of the least chemically investigated classes (Hexactinellida), were fractionated by RP-HPLC and analyzed by NMR spectroscopy and GC–MS of their pyrrolidine derivatives, methyl(ethyl) esters and their dimethyl disulfide adducts. One hundred and twenty-three C12–C31 acids (including nine new compounds) were detected, one hundred and ten of these compounds have not been found previously in glass sponges. The levels of common methylene-interrupted polyenes, monoenes of the (n–7) family and less common branched-chain components proved to be high. New acids were shown to be 5,13-dimethyl-tetradec-4-enoic, cis-10,11-methylene-heptadecanoic, 10,12-dimethyl-octadecanoic, cis-12,13-methylene-nonadecanoic, (14E)-13-methyl-eicos-14-enoic, 19-methyl-eicos-13-enoic, cis-20,21-methylene-heptacosanoic, 27-methyl-octacos-21-enoic and (22Z)-nonacos-22-enoic. Some important mass spectrometric characteristics of pyrrolidides of homologous cyclopropane fatty acids are reported and discussed.