A polysaccharide from L. flowers relieves ulcerative colitis by regulating the inflammatory signaling pathway and gut microbiota.

A polysaccharide fraction named ATFP was isolated and purified from L. flowers. Its primary structure and therapeutic effects on mice with acute ulcerative colitis were investigated in the present study. The results showed that the molecular weight of ATFP was determined to be 1.56 × 10 Da without nucleic acids and protein. Moreover, ATFP was a pyranose type acidic polysaccharide containing α and β type glycosidic bonds and consisted of Ara, Gal, Glc, Xyl, GlcA and Glca with molar percentages of 14.55 : 49.46 : 7.28 : 23.23 : 2.49 : 3.01. Microscopic observation revealed that ATFP had a smooth lamellar structure with pores and multiple molecular chains were intertwined. In animal experiments of dextran sodium sulfate-induced acute ulcerative colitis, the results indicated that ATFP significantly improved the symptom of weight loss, decreased the disease activity index and alleviated pathological damage. The anti-inflammatory mechanism of ATFP might be related to the inhibition of the TLR4/MyD88/NF-κB signaling pathway to regulate the level of inflammatory cytokines. In particular, ATFP also played an important role in regulating the structure of gut microbiota, which was specifically reflected in promoting the abundance of short-chain fatty acid producing bacteria. Overall, ATFP showed a significant mitigating effect against ulcerative colitis in mice, and it is expected to prove its value efficiently in the field of functional food.