Chemical characterization of milk oligosaccharides of the eastern quoll (Dasyurus viverrinus)

Structural characterizations of marsupial milk oligosaccharides have been performed in four species to date: the tammar wallaby (Macropus eugenii), the red kangaroo (Macropus rufus), the koala (Phascolarctos cinereus) and the common brushtail possum (Trichosurus vulpecula). To clarify the homology and heterogeneity of milk oligosaccharides among marsupials, the oligosaccharides in the carbohydrate fraction of eastern quoll milk were characterized in this study. Neutral and acidic oligosaccharides were separated and characterized by 1H-nuclear magnetic resonance spectroscopy and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The structures of the neutral oligosaccharides were Gal(β1–3)Gal(β1–4)Glc (3’-galactosyllactose), Gal(β1–3)Gal(β1–3)Gal(β1–4)Glc (3”,3’-digalactosyllactose), Gal(β1–3)[Gal(β1–4)GlcNAc(β1–6)]Gal(β1–4)Glc (lacto-N-novopentaose I), Gal(β1–3)Gal(β1–3)[Gal(β1–4)GlcNAc(β1–6)]Gal(β1–4)Glc (galactosyl lacto-N-novopentaose I), Gal(β1–3)[Gal(β1–4)GlcNAc(β1–6)]Gal(β1–3)Gal(β1–4)Glc (galactosyl lacto-N-novopentaose II), Gal(β1–3)[Gal(β1–3)Gal(β1–4)GlcNAc(β1–6)]Gal(β1–4)Glc (galactosyl lacto-N-novopentaose III) and Gal(β1–3)[Gal(β1–4)GlcNAc(β1–6)]Gal(β1–3)[Gal(β1–4)GlcNAc(β1–6)]Gal(β1–4)Glc (lacto-N-novooctaose). The structures of the acidic oligosaccharides detected are Neu5Ac(α2–3)Gal(β1–4)Glc (3’-sialyllactose), Gal(β1–3)(O-3-sulfate)[Gal(β1–4)GlcNAc(β1–6)]Gal(β1–4)Glc (lacto-N-novopentaose I sulfate a), Gal(β1–3)[Gal(β1–4)(O-3-sulfate)GlcNAc(β1–6)]Gal(β1–4)Glc (lacto-N-novopentaose I sulfate b), Neu5Ac(α2–3)Gal(β1–3)[Gal(β1–4)GlcNAc(β1–6)]Gal(β1–4)Glc (sialyl lacto-N-novopentaose a), Gal(β1–3)[Neu5Ac(α2–3)Gal(β1–4)GlcNAc(β1–6)]Gal(β1–4)Glc (sialyl lacto-N-novopentaose c), Neu5Ac(α2–3) Gal(β1–3)[Gal(β1–4)GlcNAc(β1–6)]Gal(β1–3)[Gal(β1–4)GlcNAc(β1–6)]Gal(β1–4)Glc, and Gal(β1–3)[Gal(β1–4)GlcNAc(β1–6)]Gal(β1–3)[Gal(β1–4)GlcNAc(β1–6)]Gal(β1–4)Glc with an α(2–3) Neu5Ac linked to β(1–4)Gal residue of either branch of Gal(β1–4)GlcNAc(β1–6) units. The most predominant oligosaccharides in the carbohydrate fraction of mid-lactation milk were found to be lacto-N-novopentaose I and lacto-N-novooctaose, i.e., branched oligosaccharides that contain N-acetylglucosamine. The predominance of these branched oligosaccharides, rather than of a series of linear β(1–3) linked galacto oligosaccharides, appears to be the main feature of the eastern quoll milk oligosaccharides that differentiates them from those of the tammar wallaby and the brushtail possum.