Occurrence of ceramide digalactoside as the main glycosphingolipid in the marine sponge Halichondria japonica.

The main glycosphingolipid of the sponge Halichondria japonica was isolated and its structure was determined to be ceramide digalactoside, Galα1 → 4Galβ2 →1 Cer, using FAB/MS, IR, 1H-NMR and chemical methods such as permethylation analysis and degradation techniques. The ceramide moiety was composed mainly of 4-hydroxy-iso-octadecasphinganine and 2-hydroxy-docosanoic acid. Interestingly, the branched long-chain bases were comprised of 70% total long-chain bases and 17.5% 4-hydroxy-anteiso-nonadecasphinganine. Ceramide monohexoside, consisting of galactosyl ceramide (81%) and glucosyl ceramide (19%), was also isolated as a minor component. The composition of the ceramide moiety was nearly the same as that of ceramide digalactoside.