Characterization of oligosaccharides in milk of bearded seal ( Erignathus barbatus)

Abstract

Carbohydrates were extracted from milk of a bearded seal, Erignathus barbatus (Family Phocidae). Free neutral oligosaccharides were separated by gel filtration, anion-exchange chromatography and preparative thin layer chromatography, while free acidic oligosaccharides were separated by gel filtration and then purified by ion exchange chromatography, gel filtration and high performance liquid chromatography. Oligosaccharide structures were determined by 1H-NMR spectroscopy. The structures of the neutral oligosaccharides were as follows; lactose, 2′-fucosyllactose, lacto- N-fucopentaose IV, difucosyl lacto- N-neohexaose and difucosyl decasaccharide which contained a lacto- N-neohexaose unit as well as an additional Gal(β1-4)GlcNAc(β1-3) unit and two residues of non-reducing Fuc(α1-2). The acidic oligosaccharides were thought to contain an Neu5Ac(α2-6) residue linked to GlcNAc or a sulfate linked to Gal at OH-3. The sialyl oligosaccharides and sulfated oligosaccharides had a lacto- N-neohexaose unit and two non-reducing Fuc(α1-2) residues and some of them had in addition one or two Gal(β1-4)GlcNAc(β1-3) units. The milk oligosaccharides of the bearded seal were compared to those of the harbour seal, which had been studied previously.