Fatty acids in echinoidea: Unusualcis‐5‐olefinic acids as distinctive lipid components in sea urchins

Open tubular gas liquid chromatographic (GLC) analyses of fatty acids from total lipids of 12 species of Echinoidea collected at several locations along the Pacific coast of Japan showed the same unusual cis ‐5‐olefinic acids in all species, i.e., cis ‐5‐octadecenoic acid (5–18∶1), cis ‐5‐eicosenoic acid (5–20∶1), all‐ cis ‐5,11‐ and 5,13‐eicosadienoic acids (5,11‐ and 5,13–20∶2), all cis ‐5,11,14‐eicosatrienoic acid (5,11,14–20∶3) and all‐ cis ‐5,11,14,17‐eicosatetraenoic acid (5,11,14,17–20∶4). The structural analysis of partially purified 5,11,14,17–20∶4 was undertaken by reductive ozonolysis with GLC and gas chromatographic‐mass spectrometric analyses of the products. 13 C‐Nuclear magnetic resonance analyses of the totals and fractions of fatty acid methyl esters from the sea urchin lipids did not show any occurrence of fatty acids having an isolated olefinic bond in the 2, 3 or 4 positions. The 5‐olefinic acids were concentrated on the polar lipids rather than neutral lipids. The branched and odd chain fatty acid contents of mud‐feeding sea urchins were found to be relatively greater proportions of total fatty acids than in algae feeders.