Molecular characterization of a highly heterogeneous mixture of glucosylceramides from a deep-water Mediterranean scleractinian coral Dendrophyllia cornigera

We report here on the structural characterization of a highly heterogeneous mixture of glucosylceramides (GlcCers) isolated from a deep-water Mediterr anian dendrophylliid coral, Dendrophyllia cornigera, The neutral glycosphin golipid (GSL) components of the coral were separated into three HPLC fracti ons which were structurally characterized by nuclear magnetic resonance (NM R) and mass spectrometry (MS), NMR analysis revealed a beta -glucosylpyrano se, a methyl branched conjugated sphingadienine and alpha -hydroxy fatty ac id moieties characteristic for the species. Molecular mass distributions of the HPLC fractions were monitored using single-stage MS. At least 17 diffe rent GlcCer constituents with variable long-chain base and fatty acid resid ues were observed based on the molecular ion peaks in the liquid secondary ion (LSI) survey spectra, Structures of the individual components were reve aled by product ion spectra of the alkali-cationized molecules ([M + Cat]()), which resulted in two characteristic fragment ions, F-F and F-S. Tandem MS of the same fragment ions formed in the ion source showed that FF carri es the hydoxy fatty acid, while Fs carries the long-chain sphingoid base, t hus providing complementary structural information for the characterization of ceramide composition. Based on the tandem mass spectra of the molecular ions [M + Na](+), 26 different GlcCers of the coral were identified. The c eramide moiety showed heterogeneity in both the sphingoid portion (d18:2, d 19:2, d20:2 and d20:3) and the alpha -hydroxy fatty acid chain (h19-h24, ei ther saturated or unsaturated), forming an extremely heterogeneous mixture, The method is generally applicable to the characterization of structurally heterogeneous GlcCer mixtures. Copyright (C) 2000 John Wiley & Sons, Ltd.