Preparation And Antioxidation Mechanism Of Stilibene Glycoside From Polygonum Multiflorum Thunb

Polygonum multiflorum Thunb(PM) is an earthnut plant and is typically traditional anti-aging herb in China. A lot of research has been carried out on the main functional compound-stilbene glycoside (SG) from PM in recent years. SG serves several functions, such as: antioxidant activity and free radical scavenging, anti-tumour effect, cholesterin reduction, atherosclerosis inhibition, liver protecting, vasodilation, prevention of aging dementia, improve memory etc. Antioxidant activity is the major functionality of SG. In this dissertation, the crystal of SG was separated from PM harvested in Guizhou province, and its antioxidant activity and the mechanism were studied. Also, the isolation and purification of SG from PM was conducted.The extraction and isolation of SG from PM were optimized. SG was extracted by water from PM. The optimal conditions were:50℃, 1:15 solid /liquid ratio and for 40min. Secondly, Chitosan was used to clarify crude extract of PM, and the best parameters were: chitosan addition quantity 0.3mg/mL, pH 4.5, and 20℃. Finally, macroporous adsorbent resin separation SG was carried out. On comparing the adsorption and desorption performance of 15 kinds of macroporous adsorbent resin by static adsorption test, 5 kinds of resin were picked out. Through static experiments on Freundlich and Langmuir adsorption isotherm, HPD-100 macroporous adsorbent resin was selected for it excellent performance. Afterward, the effect of concentration, pH, eluted solution and speed of infusion of HPD-100 resin were studied with dynamic adsorption test. The result showed that impurities were removed by using 20% EtOH, then SG was eluted with 40% EtOH, Thence the final product was obtained with a purity of 84.47%, and yield ratio of 75.12%. Column chromatography of polycaprolactam was used to separate EtOH extracts of PM,and then an acicular crystal was obtained by solvent evaporation. The purity of stilbene glycoside was 99.49% by HPLC analysis. The structure of crystals was determined by NMR and X-ray diffraction analysis. The physical property of crystals was also tested on DSC and TGA. The result showed that there was no polymorphism and only one acicular crystal of SG was observed. The melting point of SG was 151.33℃.Antioxidant activitity of SG, the fraction of resin (RF-SG) and ethanol extracts of PM (C-SG) were investigated. The antioxidant properties of extracts of PM were evaluated using different antioxidation tests, including reducing power, inhibition to lipid oxidation (ferric-thiocyanate), DPPH radical scavenging, superoxide anion radical scavenging, hydroxyl radical scavenging, hydrogen peroxide scavenging, and metal chelating activity, Butylated hydroxytoluene (BHT) and Vc were used as references. At the same time, the various antioxidant activities were compared with that of resveratrol (RE: a kind of structure analog).