Hydrocarbon chain distribution of ether phospholipids of the ascidian Halocynthia roretzi and the sea urchin Strongylocentrotus intermedius.

The contents and compositions of the 1-O-alk-1'-enyl-2-acyl, 1-O-alkyl-2-acyl, and 1,2-diacyl glycerophospholipids in the muscle and viscera of the ascidian Halocynthia roretzi, and of the gonad of the sea urchin Strongylocentrotus intermedius, which are eaten to some extent in Alaska and in Asia, were analyzed by gas-liquid chromatography. 1-O-Alk-1'-enyl-2-acyl glycerophospholipids were found in all of the samples, accounting for 64.4-69.0% of the ethanolamine glycerophospholipid (EPL). By contrast, the levels of the 1-O-Alk-1'-enyl-2-acyl choline glycerophospholipids (CPL) were low (3.1-5.7%). CPL was rich in the 1-O-alkyl-2-acyl subclass amounting to 12.5-23.9% in the ascidian sample. The level of CPL in the sea urchin gonad was extremely high, amounting to 46.1%. The most prominent alkyl chains in the sn-1 position of CPL from the ascidian muscle were 16:0 (44.6%), 18:1 (26.5%), and 18:0 (10.7%), and of CPL from the sea urchin gonad were 18:0 (36.2%), 16:0 (33.0%), and 18:1 (17.8%). Unusually high levels of odd-numbered alkyl chains, e.g., 19:0 and anteiso 17:0, were detected in the CPL of all samples. The prominent alkenyl chains of EPL were 18:0 (69.4%), 16:0 (10.0%), and 18:1 (8.54%) (not counting the vinyl double bond) for the sea urchin gonad. Relatively high levels of 20:1 alkenyl chains were also present. The glycerol sn-2 positions contained high proportions of polyunsaturated fatty acids. Thus, 20:5n-3 (43.6%) and 22:6n-3 (20.1%) were most abundant in the alkylacyl CPL from the ascidian muscle and 20:5n-3 (54.9%) and 20:4n-6 (30.1%) in alkylacyl CPL from the sea urchin gonad. Despite a possible interconversion of the alkyl and alkenyl chains of each class of the ether phospholipids, they showed few features in common.