Dendrobium officinale polysaccharides alleviated DSS-induced ulcerative colitis in mice through remolding gut microbiota to regulate purine metabolism

• DOP is effective in relieving symptoms of UC in mice. • DOP improved intestinal mucosal barrier function and reduced inflammation. • DOP improved the structure of gut microbiota in UC mice. • DOP mainly affects metabolic pathways such as purine metabolism to improve UC. Dendrobium officinale (DO) has no side effects and has been used for centuries to treat gastrointestinal diseases in China. Polysaccharides are the primary components of DO (referred to as DOP). In this study, leaf polysaccharides (DOPY) and stem polysaccharides (DOPJ) were extracted to investigate the protective effect on dextran sodium sulfate (DSS)-induced ulcerative colitis (UC) in mice and explore its mechanisms of action through analyzing the intestinal microbiota and metabolites in cecum contents. The results showed that DOP reduced the disease activity index (DAI), improved colonic pathology, and protected the integrity of the intestinal barrier (Occludin and Muc2) in UC mice. 16S rRNA sequencing suggested that DOP increased the abundance of beneficial bacteria ( Turicibacter and Romboutsia ) and reduced the abundance of harmful bacteria ( Escherichia-Shigella and Parvibacter ). Metabolomic analysis revealed that DOP regulated purine metabolism in the intestine, thereby maintaining intestinal mucosal immune homeostasis. These findings suggested that DOP exerted promising protection against DSS-induced ulcerative mice through remolding gut microbiota to regulate purine metabolism.