Characterization of Ganglioside GM4 Lactones Isolated from the Whale Brain

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Abstract
Two novel ganglioside lactones were isolated from the brain of Bryde's whale (Balaenoptera edeni) and scharacterized. These gangliosides migrated above GM4 and were designated M4-1 and M4-2 in the order of location from the bottom of the TLC plate. These gangliosides were converted to GM4 by mild alkali treatment. Although M4-1 and M4-2 contained 1 mol each of N-acetylneuraminic acid and galactose, they behaved as neutral lipids on ion-exchange chromatography. Inner ester linkages were found in these gangliosides by secondary ion mass spectrometry and infrared spectroscopy. Two dimensional J-correlated proton NMR spectra revealed that an inner ester linkage was formed in M4-1 between the sialic acid carboxyl group and the C-4 hydroxyl group of the galactosyl residue and another inner ester linkage was formed in M4-2 between the sialic acid carboxyl group and the C-2 hydroxyl group of galactose.