9-chloro-5,9-dienoic and other fatty acids from marine sponge <i>Penares</i> sp.

Abstract

The fatty acids and their ethyl esters from an extract of a sponge Penares sp. (South China Sea) were fractionated by high-performance liquid chromatography and analyzed by gas chromatography-mass spectrometry using pyrrolidine, 4,4-dimethyloxazoline, dimethyl disulfide, and hydrogenated derivatives. In some cases, 1Н and 13С NMR spectroscopy was applied for the structural analysis of fatty acids. 71 С12–С28 acids, including 12 new compounds, were found. The new compounds were shown to be (5Z,9Z)-9-chloro-24-methy-5,9-pentacosadienoic, (5Z,9Z)-9-chloro-25-methyl-5,9-hexacosadienoic, (5Z,9Z)-9-chloro-24-methyl-5,9-hexacosadienoic, (5Z,9Z)-9-chloro-25-methyl-5,9-heptacosadienoic, 6-chloro-20-methyl-4-heneicosenoic, 6-chloro-19-methyl-4-heneicosenoic, 6-chloro-20-methyl-4-docosenoic, cis-17,18-methylene-tetracosanoic, 16,21-dimethyldocosanoic, 18,23-dimethyltetracosanoic, 16,18,22-trimethyltricosanoic, and 18,20,24-trimethylpentacosanoic acids. It was shown that the characteristic features of the fatty acid mixture were a high level of constituents with monomethylated chains (over 50%) and the nearly total substitution of common demospongic acids for their chloro-derivatives, previously unknown (5Z,9Z)-9-chloro-5,9-dienoic acids. The presence of analogous structural fragments in the fatty acids from Penares sp. and in some biologically active secondary metabolites from Penares sponges was discussed. The results of this work may be used for the structural, comparative and biosynthetic studies of marine lipids.