Determination of each neutral oligosaccharide in the milk of Japanese women during the course of lactation

Using reverse-phase HPLC after pyridylamination, we quantified the concentrations of major neutral oligosaccharides in the milk of sixteen Japanese women collected at 4, 10, 30 and 100 d postpartum. In colostrum and mature milk (30 d lactation), lacto-N-fucopentaose (LNFP) I was the most abundant oligosaccharide, followed by 2′-fucosyllactose (2′-FL) + lacto-N-difucotetraose (LNDFT), LNFP II + lacto-N-difucohexaose II (LNDFH II), and 3-fucosyllactose (3-FL). Together these accounted for 73 % of the total weight of neutral oligosaccharides in colostrum and mature milk. Changes in concentration occurred during the course of lactation. LNFP I and 2′-FL + LNDFT increased from 4 to 10 d postpartum, and then declined by 100 d. LNFP II + LNDFH II steadily increased during the first 30 d and then declined. In contrast, 3-FL increased steadily throughout the entire 100 d of study. Large differences were observed between our data and previously published data in Italian women, in terms of both the concentration and temporal changes of each oligosaccharide. These differences may be caused by different assay methodology, although racial differences cannot be ruled out.

Species specificity of O-linked carbohydrate chains of the oviducal mucins in amphibians: structural analysis of neutral oligosaccharide alditols released by reductive β-elimination from the egg-jelly coats of Rana clamitans

The extracellular matrix (the so-called jelly coat) surrounding amphibian eggs mainly comprises highly O-glycosylated proteins. These oviducal mucins have an important role in the fertilization process, and their carbohydrate chains are remarkably species-specific. Alkaline reductive treatment of the jelly-coat material of the frog Rana clamitans led to the release of oligosaccharide alditols. The neutral oligosaccharide alditols were fractionated and purified by successive chromatographic techniques. The structures of 27 of them, ranging from three to sixteen monosaccharides, were established by a combination of NMR spectroscopy, methylation analyses and matrix-assisted laser-desorption ionization—time of flight MS. Typically, some of the neutral compounds appeared to possess the core structure: Gal(β1–3)[GlcNAc(β1–6)]Gal(β1–3)[GlcNAc(β1–6)]GalNAc-ol (where GalNAc-ol represents N-acetylgalactosaminitol). Moreover, a novel type of chain termination, characterized by an unusual sequence {Fuc(α1–2)Gal(α1–3)Gal(α1–4)Gal(β1–3/4)} was observed. Indeed, the most complex representative structure of this series was found to be: Fuc(α1–2)Gal(α1–3)Gal(α1–4)Gal(β1–3)[Fuc(α1–2)Gal(α1–3)Gal(α1–4)Gal(β1–4)GlcNAc(β1–6)]Gal(β1–3)[Fuc(α1–2)Gal(α1–3)Gal(α1–4)Gal(β1–4)GlcNAc(β1–6)]GalNAc-ol.

Neutral oligosaccharide content of preterm human milk

Human milk oligosaccharides are known to play a role in protection against certain infectious diseases. Previous reports indicate that the content of human milk oligosaccharides varies widely among individuals at term but such information on preterm milk is lacking. After removal of the fat, protein and most of the lactose from non-pooled human milk samples, a total neutral oligosaccharide fraction was isolated by ion-exchange chromatography followed by gel filtration. A Dionex high-performance anion-exchange chromatography system equipped with a pulsed electrometric detector was then employed to measure the levels of ten neutral oligosaccharides in the individual milk samples. Twenty-three milk samples from thirteen mothers who delivered at a mean gestational age of 29·5 (sd 3·1) weeks were collected between days 0 and 33 of lactation, and compared with three samples of term milk from two mothers. The ranges of the total and individual levels of the ten neutral oligosaccharides in preterm milk were similar to those in term milk. Further, as previously described in term milk, preterm milk exhibited a quantitative individual variation. This variation was independent of the gestational age, day of lactation, and postconceptional age. In conclusion, levels of ten neutral oligosaccharides did not differ between preterm and term human milk.