Sphingolipids of Euhadra hickonis. III. Ceramides of the Viscera.

Abstract

Structural studies on two ceramides (ceramide-I and ceramide- II) isolated from viscera of Euhadra hickonis, a Pulmonate, were carried out using fast atom bombardment mass spectrometry (FAB/MS), gas chromatography (GC), gas chromatography-mass spectrometry (GC-MS) and usual chemical methods. The major fatty acids of ceramide-I were hexadecanoic (19.6%) and 2-hydroxyhexadecanoic acids (14.3%), and that of ceramide- II was 2-hydroxyhexadecanoic acid (39.5%). The major long-chain bases of ceramide- I were 2-amino-16-methyl-4-octadecene-1, 3-diol (39.8%) and 2-amino-4- octadecene-1, 3-diol(19.6%), and that of ceramide-II was 2-amino-16-methyl-octadecane-1, 3, 4-triol (47.2%). The structures of the major molecular species of ceramide-I were found to be N-hexadecanoyl-2-amino-16-methyl-4-octadecene-1, 3-diol and N-2-hydroxyhexadecanoyl-2-amino-16-methyl-4-octadecene-1, 3-diol, and that of ceramide- II was N-2-hydroxyhexadecanoy1-2-amino-16-methyl-octade-ane-1, 3, 4-triol.The most remarkable feature of the long-chain bases of ceramides in viscera of E. hickonis was the large amount of branched long-chain bases. To determine the pathway for the synthesis of sphingolipids in E. hickonis, the molecular species of ceramide-I and - II were compared with those of the ceramide moieties of ceramide monohexosides and sphingophosphonolipids.