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 H 2 O 2 , 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.