Identification of novel nonmethylene‐interrupted fatty acids, 7<i>E</i>,13<i>E</i>‐20∶2, 7<i>E</i>,13<i>E</i>,17<i>Z</i>‐20∶3, 9<i>E</i>,15<i>E</i>,19<i>Z</i>‐22∶3, and 4<i>Z</i>,9<i>E</i>,15<i>E</i>,19<i>Z</i>‐22∶4, in ophiuroidea (Brittle star) lipids

Abstract

Fatty acids of Ophiuroidea (brittle star) Ophiura sarsi have been investigated by gas-liquid chromatography (GLC). About 2-13% of four unidentified fatty acids were found in total fatty acids from a sample caught at a depth of 1,100 m. Structural analyses were undertaken after partial hydrogenation of their concentrates with hydrazine hydrate and subsequent isolation of the monoenoate products by argentation thin-layer chromatography. The structures of the unidentified fatty acids were determined as 7E,13E-eicosadienoic (20:2), 7E,13E,17Z-eicosatrienoic (20:3), 9E,15E,19Z-docosatrienoic (22:3), and 4Z,9E,15E,19Z-docosatetraenoic (22:4) acids by gas chromatography-mass spectrometry of dimethyl disulfide adducts and GLC of the monoenoates on a polar column. These fatty acids belong to a family of nonmethylene-interrupted (NMI) polyunsaturated fatty acids frequently observed in marine invertebrates and conifer seeds. As far as the authors know, however, these NMI fatty acid types with mixed geometry of ethylenic bonds have not been reported previously.