Pectic polysaccharides from Polygonum cuspidatum: structural characterization and protective effects against DSS-induced colitis.

The dried rhizomes and roots of Polygonum cuspidatum (PC) is a frequently used traditional Chinese medicine with the potential for treating gastrointestinal diseases. However, it is still uncertain whether the macromolecular polysaccharides, especially those of non-glucan types, play an important role in preventing intestinal inflammatory disease. In this study, an acidic polysaccharide (PCP-I) with a molecular weight of 134.45 kDa was isolated from PC, consisting of GalA, Gal, Ara, Rha, Glc and GlcA in a molar ratio of 50.4:25.8:14.0:5.9:3.4:0.5. It was characterized as a pectic-type polysaccharide with homogalacturonan (HG, 44.5%) chains and a rhamnogalacturonan I (RG-I, 51.6% with branching degree of 6.75) region, with a HG/RG-I ratio of 0.86 and was lightly methyl-esterified. Side chains attached to RG-I could be mainly type II arabinogalactans, followed by arabinan and type I arabinogalactans with an approximate ratio of 5:2:1. PCP-I was shown to relieve the symptoms of experimental colitis induced by dextran sodium sulfate, with inhibition of colonic inflammation and potential restoration of barrier function, possibly through the inhibition of TLR4/MyD88/NF-κB on the transcriptional level. The promising effects could be due to the restoration of gut microbiota composition, as two potential probiotic genera Alistipes and Akkermansia were promoted. Overall, these findings revealed that the PCP-I, a pectic polysaccharide in PC, could be a key contributor to its function of preventing colitis, and possesses the potential of being a preventive agent deserving further investigation for intestinal inflammatory disease.