Study On Decolorization Process And Biological Activity Of Rehmannia Glutinosa Polysaccharide

Rehmannia glutinosa polysaccharide（RGP）is an important active ingredient in natural Rehmannia glutinosa has the functions of enhancing immune function,anti-oxidation,anti-tumor,regulating blood sugar and blood lipids,etc.It was applied widly in the field of food,medicine and health care products.In this study,single-factor experiment design and response surface optimization were used to optimize the decolorization process of RGP.The structure of RGP was characterized by Fourier transform infrared spectroscopy（FTIR）and nuclear magnetic resonance（NMR）after separation and purification.LPS-induced piglet intestinal epithelial cells（IPEC-J2）and immune stress models in mice were constructed to evaluate the biological activity of RGP.Below are key research results:1.Single factor experiment design and response surface methology were used to optimize the decolorization process of RGP with AB-8 macroporous resin.The optimal decolorization parameters were as follows:temperature 50℃,8.4%macroporous resin,decolorization time 64 min,and p H 5.0.The RGP-1-A was abtained,the overall score was65.29%,molecular weight was 18964 Da,the total sugar content was 88.24%,the uronic acid content was 19.02%,and the sulfate group content was 11.83%.2.Single factor experiment design and response surface methology were used to optimize the decolorization process of RGP with H₂O₂.The optimal decolorization parameters were as follows:temperature 51℃,decolorizationtime 2 h,p H 8.6,and 9.5%H₂O₂.The RGP-2-A was prepared with molecular weight of 3305 Da,91.54%total sugar,1.1%uronic acid,and 8.56%sulfate group.3.Fourier transform infrared spectroscopy and other methods were used to analyze the physical and chemical properties and structure characterization of the two RGPs.The results showed that RGPs had polysaccharide characteristic groups,and both contained glucose,galactose,arabinose,galacturonic acid and rhamnose,but the ratio of monosaccharides was different.X-ray diffraction results showed that both RGPs were amorphous.Scanning electron microscope results showed that RGP-1-A was in the shape of irregular large curly flakes,while RGP-2-A was in the shape of fine flakes.4.The in vitro antioxidant test of RGPs was carried out by DPPH,ABTS and hydroxyl radical methods.The results showed that the scavenging abilities of RGPs on DPPH,ABTS and hydroxyl radicals were dose response,and RGP-1-A had better effect than RGP-2-A on DPPH,ABTS and hydroxyl radical scavenging abilities at the same content.The IPEC-J2cell inflammation model induced by LPS was used to investigate the anti-inflammatory effect and mechanism of RGPs.The results showed that:compared with the model group,RGPs could activate downstream genes（HO-1 and NOQ1）,promote the production of intracellular antioxidant enzymes（SOD）and inhibite pro-inflammatory factors（TNF-α,IL-1βand IL-6）and lipid peroxide（MDA）production by regulating the Nrf2/keap1antioxidant pathway and the TLR4/NF-κB inflammatory pathway,then improved the abilities of cells anti-oxidation and anti-inflammation.In addition,RGPs significantly increased the m RNA expression abundance of barrier function-related genes（Occludin,MUC-2,Claudin-1,and ZO-1）,and strengthened the intestinal barrier function.5.LPS-induced liver injury model was used to explore the effect and mechanism of RGPs on liver injury of mice.The results showed that compared with the model group,RGPs regulate the TLR4/My D88/NF-κB signaling pathway in the liver,reduce the gene expression of pro-inflammatory factors（TNF-α,IL-1β,IL-6,caspase-1）in vivo and increase the anti-inflammatory factors（IL-10）gene expression,reduce the content of AST,ALT,ALP enzyme activity and TBIL in mice,reduce the content of lipid peroxidation（MDA）and catalase（CAT）in mice,and increase antioxidant enzymes（SOD）content,thereby improving the degree of liver inflammation in mice.