Rehmannia glutinosa Polysaccharides: Optimization of the Decolorization Process and Antioxidant and Anti-Inflammatory Effects in LPS-Stimulated Porcine Intestinal Epithelial Cells

Polysaccharide decolorization has a major effect on polysaccharide function. In the present study, the decolorization of Rehmannia glutinosa polysaccharides (RGP) is optimized using two methods-the AB-8 macroporous resin (RGP-1) method and the H2O2 (RGP-2) method. The optimal decolorization parameters for the AB-8 macroporous resin method were as follows: temperature, 50 degrees C; macroporous resin addition, 8.4%; decolorization duration, 64 min; and pH, 5. Under these conditions, the overall score was 65.29 +/- 3.4%. The optimal decolorization conditions for the H2O2 method were as follows: temperature, 51 degrees C; H2O2 addition, 9.5%; decolorization duration, 2 h; and pH, 8.6. Under these conditions, the overall score was 79.29 +/- 4.8%. Two pure polysaccharides (RGP-1-A and RGP-2-A) were isolated from RGP-1 and RGP-2. Subsequently, their antioxidant and anti-inflammatory effects and mechanisms were evaluated. RGP treatment activated the Nrf2/Keap1 pathway and significantly increased the activity of antioxidant enzymes (p < 0.05). It also inhibited the expression of pro-inflammatory factors and suppressed the TLR4/NF-kappa B pathway (p < 0.05). RGP-1-A had a significantly better protective effect than RGP-2-A, likely owing to the sulfate and uronic groups it contains. Together, the findings indicate that RGP can act as a natural agent for the prevention of oxidation and inflammation-related diseases.

Automated summary

In this study, the optimization of the decolorization methods for Rehmannia glutinosa polysaccharides (RGP) was investigated. The AB-8 macroporous resin and H2O2 methods were used. The optimal conditions for the AB-8 macroporous resin method were temperature of 50°C, resin addition of 8.4%, duration of 64 minutes, and pH of 5, with an overall score of 65.29 +/- 3.4%. For the H2O2 method, the optimal conditions were temperature of 51°C, H2O2 addition of 9.5%, duration of 2 hours, and pH of 8.6, with an overall score of 79.29 +/- 4.8%. The isolated polysaccharides, RGP-1-A and RGP-2-A, exhibited antioxidant and anti-inflammatory effects through activation of the Nrf2/Keap1 pathway and suppression of the TLR4/NF-kappa B pathway.