Structural Characteristics of Rehmannia glutinosa Polysaccharides Treated Using Different Decolorization Processes and Their Antioxidant Effects in Intestinal Epithelial Cells.

Polysaccharide decolorization is a key determinant of polysaccharide structure. In this study, two purified Rehmannia glutinosa polysaccharides, RGP-1-A and RGP-2-A, were obtained after decolorization using the AB-8 macroporous resin and H2O2, respectively. RGP-1-A (molecular weight (Mw) = 18,964 Da) and RGP-2-A (Mw = 3305 Da) were acidic and neutral heteropolysaccharides, respectively, and were both polycrystalline in structure. FTIR analysis revealed that RGP-1-A was a sulfate polysaccharide, while RGP-2-A had no sulfate group. Experiments on IPEC-1 cells showed that RGPs alleviated oxidative stress by regulating the Nrf2/Keap1 pathway. These findings were confirmed by the upregulation of Nrf2, NQO1, and HO-1; the subsequent increase in the levels of antioxidant indicators (SOD, LDH, CAT, and MDA); and the restoration of mitochondrial membrane potential. Overall, the antioxidant capacity of RGP-1-A was significantly higher than that of RGP-2-A. These results suggest that RGPs may be a potential natural antioxidant and could be developed into functional foods.

Structural Characteristics of Inulin and Microcrystalline Cellulose and Their Effect on Ameliorating Colitis and Altering Colonic Microbiota in Dextran Sodium Sulfate-Induced Colitic Mice.

Several studies have reported that dietary fibers (DFs) from plants may exert beneficial effects on inflammatory bowel disease. In the present study, we investigated the structural differences of soluble DF (inulin) and insoluble DF (microcrystalline cellulose, MCC) and their effects on the intestinal barrier integrity, gut microbiota community, and inflammation response in mice with dextran sodium sulfate (DSS)-induced colitis. Mice were fed for 21 days with diets containing inulin or MCC (2.5 g/kg body weight), and colitis was induced by administration of DSS (4% w/v) in drinking water during the last 8 days of experimentation. The results showed that inulin and MCC differ in morphology and structure. MCC exhibited a smaller particle size, a larger specific surface area, and higher thermal stability than inulin. In addition, both inulin and MCC restored various physical signs (body weight, colon weight and length, disease activity index score, and infiltration of inflammatory cells), gut barrier function (as evidenced by the increased expression of claudin-3, claudin-7, ZO-2, occludin, JAM-2, and MUC-3 and the decreased activity of myeloperoxidase activity), downregulation of mRNA expression of proinflammatory cytokines (caspase-1, NLPR3, TLR4, TNF-α, and IL-1ß), and modulation of colon microbiota community. Taken together, the present study demonstrates that DFs differ in morphology and structure and ameliorate DSS-induced colitis in mice by blocking proinflammatory cytokines, reinforcing gut barrier integrity, and modulating gut microbiota. Therefore, DFs, especially inulin, are promising dietary supplements to alleviate intestinal inflammation.