A new perspective on structural characterisation and immunomodulatory activity of arabinogalactan in Larix kaempferi from Qinling Mountains.

In this study, crude polysaccharide (LAG-C) and homogeneous arabinogalactan (LAG-W) were isolated from Qinling Larix kaempferi of Shaanxi Province. Bioactivity assays showed that LAG-W and LAG-C enhanced the phagocytic ability, NO secretion, acid phosphatase activity, and cytokine production (IL-6, IL-1ß, and TNF-α) of RAW264.7 macrophages. Notably, LAG-W exhibited a significantly stronger immunomodulatory effect than LAG-C. The primary structure of LAG-W was characterised by chemical methods (monosaccharide composition, methylation analysis, and alkali treatment) and spectroscopic techniques (gas chromatography-mass spectrometry, high-performance liquid chromatography-mass spectrometry, and 1D/2D nuclear magnetic resonance). LAG-W was identified as a 22.08 kilodaltons (kDa) neutral polysaccharide composed of arabinose and galactose at a 1:7.5 molar ratio. Its backbone consisted of repeated →3)-ß-Galp-(1→ residues. Side chains, connected at the O-6 position, were mainly composed of T-ß-Galp-(1→ and T-ß-Galp-(1→6)-ß-Galp-(1→ residues. And it also contained small amounts of T-ß-Arap-(1→, T-α-Araf-(1→6)-ß-Galp-(1→6)-ß-Galp-(1→, and T-α-Araf-(1→3)-α-Araf-(1→6)-ß-Galp-(1→ residues. By structurally and functionally characterising L. kaempferi polysaccharides, this study opens the way for the valorisation of this species.

Impact of structurally diverse polysaccharides on colonic mucin O-glycosylation and gut microbiota.

Understanding how dietary polysaccharides affect mucin O-glycosylation and gut microbiota could provide various nutrition-based treatments. Here, the O-glycan profile of the colonic mucosa and gut microbiome were investigated in C57BL/6J mice fed six structurally diverse dietary polysaccharides and a mixture of six fibers. Dietary polysaccharides increased total O-glycans, mainly by stimulating neutral glycans. Highly branched arabinogalactan promoted terminally fucosylated core 1 O-glycans; whereas linear polysaccharides, including pectin, konjac glucomannan, inulin, and the fiber mixture, favored terminally di-fucosylated O-glycans. The last three polysaccharides also lowered the level of sulfated O-glycans and sialylated mono-fucosylated O-glycans. Varied monosaccharide composition in mixed polysaccharides had a synergistic beneficial effect, boosting fucosylated neutral glycans, decreasing acidic glycans, and stimulating microbial richness and diversity. Dietary polysaccharides containing arabinose and sulfate groups enhanced the relative abundances of Akkermansia and Muribaculaceae, respectively. The present comparison reveals the relationship between dietary polysaccharide structure, mucin O-glycan composition, and intestinal microorganisms.