Isolation of 2-methyl branched unsaturated very long fatty acids from marine sponge Halichondria panicea and identification of them by GC–MS and NMR

Abstract

In order to study the biomarker fatty acids of symbionts in the marine sponge Halichondria panicea, purification and structural identification of two new 2-methyl branched monoenoic very long fatty acids (2-Me-24:1 n-7 and 2-Me-26:1 n-9) were performed for the first time. These acids amounted to 7.1% of total sponge FAs, but our attempts to determine their structures by one-step GC–MS analysis were unsuccessful because of low yields of the correspondent N-acyl pyrrolidide derivatives. Silver-ion thin-layer chromatography isolated enriched fractions of monoenoic fatty acids extracted from the sponge. Further purification of unknown fatty acid methyl esters was carried out by reversed-phase high-performance liquid chromatography. Determination of the chain length, degree and position of unsaturations was achieved by gas chromatography–mass spectrometry on methyl esters and dimethyldisulfide adducts. Structures, position of methyl substitution, and double bonds cis isomery were confirmed by 1 H nuclear magnetic resonance.