A low-molecular-weight carbohydrate fraction from Salvia miltiorrhiza mitigates DSS-induced colitis

Plant polysaccharides are functional carbohydrates with diverse structures and close interactions with the gut microbiota. Here, a low-molecular-weight neutral carbohydrate fraction, SMP-1, was isolated from Salvia miltiorrhiza and characterized for molecular weight, monosaccharide composition, linkage features, and selected NMR correlations. SMP-1 showed an apparent molecular weight of approximately 3.3 kDa. Complementary monosaccharide analyses indicated Gal, Glc, and Ara as the main detected sugars, with trace Fru. Methylation analysis mainly described the Galp/Glcp-rich portion and suggested abundant terminal Galp, 6-linked Galp, and 6-linked Glcp residues, whereas Fru-derived linkages were not resolved under the present methylation-GC-MS conditions. NMR analysis supported major Glcp/Galp spin systems and Fruf-containing residues, but a complete repeating-unit structure was not assigned. In a dextran sulfate sodium-induced colitis model, oral SMP-1 alleviated body weight loss, disease activity, colon shortening, and mucosal injury; restored mucus secretion and tight junction integrity; reduced pro-inflammatory cytokines; and suppressed TLR4/NF-κB signaling. SMP-1 also partially restored microbial diversity and reshaped DSS-disrupted gut microbial composition, while antibiotic-mediated microbiota depletion weakened its protective effects. These findings suggest that SMP-1 improves colitis-associated intestinal dysfunction through regulation of gut microbiota, epithelial barrier integrity, and inflammatory responses.