Ceramide Dihexosides from the Spermatozoa of the Starfish, Asterias amurensis, Consist of Gentiobiosyl-, Cellobiosyl-, and Lactosylceramide

Abstract

Ceramide dihexoside was obtained from the spermatozoa of the starfish, Asterias amuren-sis. Gas-liquid chromatography of the methanolysate to determine the sugar composition of the lipid demonstrated an unequal ratio of glucose and galactose, implying that two or more glycolipids are present. They were separated by thin-layer chromatography on a borate-impregnated plate into two bands. From the results of metbylation analysis and chromic acid oxidation, one was determined to be lactosylceramide, while the other was suggested to be a mixture of two diglucosylceramides: gentiobiosylceramide (Glcβ1-6Glcβ1-1Cer) and cellobiosylceramide (G1cβ1-4G1cβ1-1Cer). The molar ratio of gentiobiosyl-, cello-biosyl-, and lactosylceramide was estimated to be 0.7 : 0.3 : 1.0. Ceramide dihexosides obtained from another batch of the spermatozoa, collected at the same place in a different year, consisted almost exclusively of gentiobiosylceramide as confirmed by proton-nuclear magnetic resonance spectroscopy and fast-atom bombardment mass-spectrometry. The fatty acid compositions of these glycolipids were similar and the main acids were 14h:0, 15h:0, 16h:0, 18h:0, and 24h:1 (constituting more than 80% of the total acids). The long-chain base compositions were qualitatively similar and the major constituents were commonly d18: 2, d18:3, d19: 3, d22: 2, and t22:1. Lactosylceramide was rich in t22:1, while diglucosylceramides were rich in d22:2.