Polysaccharide from steamed Polygonatum sibiricum ameliorates ulcerative colitis by protecting the intestinal mucosal barrier and regulating gut microbiota.

Steamed Polygonatum sibiricum is widely applied in clinical practice for its tonic effect on gastrointestinal tract. A novel polysaccharide named PSSP-EF was extracted from the steamed roots of Polygonatum sibiricum using hot water extraction, ethanol precipitation, and chromatographic purification. PSSP-EF, with a molecular weight of 2.24 × 104 Da, was consisted of mannose, glucosamine hydrochloride, glucose, galactose, xylose, and arabinose in a molar ratio of 10.25: 0.26: 3.56: 80.55: 1.72: 3.66, and its main chain was constituted by→4)-β-D-Galp-(1→4)-β-D-Galp-(1→ and →4)-β-D-Manp-(1→4)-β-D-2ace-Manp-(1→ residues, with branching from β-D-Galp-(1→ residues. PSSP-EF could dramatically relieve clinical symptoms of ulcerative colitis (UC) in mice. Treatment with PSSP-EF significantly alleviated colon inflammation (TNF-α, IL-1β, and IL-6), repaired intestinal mucosal barrier (Occludin, ZO-1, and Claudin-1) and regulated the balance of gut microbiota by increased the levels of Muribaculaeae, while decreasing the levels of Bacteroides, Erysipelatoclostridium, and Romboutsia. Notably, PSSP-EF remarkably increased the levels of acetic, propionic, isobutyric, butyric, valeric, and isovaleric acid in the cecal contents of UC mice. In conclusion, PSSP-EF has a significant therapeutic effect on UC by balancing gut microbiota, protecting intestinal mucosal barrier, and regulating short-chain fatty acid production, and can be developed as a functional food.