Damicoside from Axinella damicornis:: The influence of a glycosylated galactose 4-OH group on the immunostimulatory activity of α-galactoglycosphingolipids

alpha-Galactoglycosphingolipids (alpha-GaIGSLs) are unique immunostimulatory glycosphingolipids from marine sponges. Analysis of the glycosphingolipid composition of the marine sponge Axinella damicornis revealed the presence of a new (alpha-GaIGSL, damicoside (3a), which is the first alpha-GalGSL with a glycosylated galactose 4-OH group. Structure elucidation of damicoside was performed using spectroscopic and chemical methods. When tested in a spleen cell proliferation assay, 3a exhibited a stimulatory activity comparable to that of agelasphin (2), showing that a free galactose 4-OH group is not essential for the immunostimulatory activity of alpha-GaIGSLs and providing a further step toward the complete understanding of their structure -activity relationship.