Structural characterization and gut modulatory activity of an arabinogalactan-rich polysaccharide from Chimonanthus salicifolius in DSS-challenged mice.

Structural diversity is a major determinant of the biological properties of plant polysaccharides, yet purified polysaccharides from Chimonanthus salicifolius leaves remain insufficiently characterized. In this study, CSP-2 A, an arabinogalactan-rich polysaccharide fraction, was purified from C. salicifolius leaves and characterized to examine its structural features and gut-associated biological responses. CSP-2 A had a weight-average molecular weight of 105 kDa and was predominantly composed of arabinose and galactose. Monosaccharide composition, methylation analysis, FTIR, and multidimensional NMR spectroscopy supported a tentative AG-II-like structural model characterized by a Gal-rich framework with multiple substituted Galp residues and terminal Araf, Arap, and Glcp residues. CSP-2 A showed concentration-dependent DPPH and ABTS radical-scavenging activities, promoted the growth of Lacticaseibacillus paracasei under the tested conditions, and showed low hemolytic activity and low irritation potential in hemolysis and HET-CAM assays. In DSS-challenged mice, CSP-2 A attenuated colon shortening and histological injury, preserved goblet cells, and reduced colonic IL-6, IL-1β, and TNF-α mRNA expression. CSP-2 A treatment was also associated with changes in gut microbial composition and partial recovery of fecal SCFAs, including a significant increase in butyrate. Untargeted metabolomics revealed broader changes in fecal metabolic profiles, with KEGG pathway analysis highlighting pathways related to tryptophan metabolism and bile secretion. Correlation analysis further revealed coordinated associations among microbial taxa, SCFAs, fecal metabolites, and inflammatory indices. These findings expand current knowledge of C. salicifolius polysaccharides by characterizing a purified arabinogalactan-rich fraction and linking this structurally characterized material with coordinated intestinal, microbial, and metabolic responses under DSS challenge.