Study On Antioxidant And Hypoglycemic Effects Of Tea Polysaccharides

Tea polysaccharides were another important functional component that was found following tea polyphenol, which possessed high antioxidant and hyperglycemic activities. The characteristics and biochemical activities of tea polysaccharidess had variety diversity. In the present study, tea varieties with high and low polysaccharides activity which preliminarily screened in our prophase study were collected and polysaccharides were extracted. Then, tea polysaccharides activity screening was verified and two polysaccharides that labeled as T01-TPS with high antioxidant activity and T09-TPS with low antioxidant activity respectively were screened. In order to investigate the antioxidant activity difference of TPS in vitro and in vivo and the association of antioxidant and hypoglycemic activity as well as its possible mechanism, activity difference of T01-TPS and T09-TPS was evaluated and compared by methods of free radical scavenging in vitro, anti-lipid peroxidation in vitro and antioxidant and hypoglycemic effect animal experiment, so as to provide evidence for the elucidation of structure-activity relationship of TPS, the breeding of variety with high polysaccharides activity, and the exploitation of functional TPS products. Main achievements were summarized below.1 Verification of TPS activity screening of different tea varietiesThirteen tea varieties with high and low polysaccharides activity which preliminarily screened in our prophase study were collected and polysaccharides were extracted. Scavenging activity of TPS to hydroxyl radical and superoxide anion free radical were determined. The results showed that the scavenging activity of different tea varieties to·OH and O2-·had significant differences and the scavenging activity of all the tea varieties to·OH and O2-·exhibited consistence to some extent. Tea varieties which had higher scavenging activity to·OH also showed stronger ability to scavenge O2-·, and the converse was true as well. Based on the two free radical scavenging activity experiments, TOl was selected as variety with high polysaccharides activity and T09 as variety with low polysaccharides activity. 2 Study on antioxidant effect of T01-TPS and T09-TPS(1) The scavenging activity of T01-TPS and T09-TPS to·OH, O2-·and DPPH were measured by the method of deoxyribose, xanthine oxidase and spectrophotometry. Results demonstrated that both T01-TPS and T09-TPS had good free radical scavenging activity. The 50% inhibition concentration (IC50) of T01-TPS and T09-TPS to·OH was 1.14 mg/mL and 2.47 mg/mL; IC50 of T01-TPS and T09-TPS to O2-·was 0.68 mg/mL and 2.94 mg/mL; IC50 of TO 1-TPS and T09-TPS to DPPH was 0.18 mg/mL and 0.09 mg/mL.(2) Effect of T01-TPS and T09-TPS on lipid-peroxidation in vitro was studied. The results showed that both T01-TPS and T09-TPS could effectively inhibit oxidative hemolysis of erythrocyte induced by H2O2, MDA formation induced by thiobarbituric acid in mice liver and the swelling of mice liver mitochondria, T01-TPS performed better effect on lipid-peroxidation than T09-TPS.(3) Hepatoprotective and antioxidant activity of T01-TPS and T09-TPS were studied using CCl4-induced acute liver injury model. The results showed that both T01-TPS and T09-TPS could remarkably suppress the increase of the activities of ALT and AST and increase albumin content in serum, and could significantly decrease MDA and NO level, while increase SOD, CAT and GSH-Px activity evidently in liver from liver-injured mice induced by CCl4. The results of liver pathological observation also suggested that T01-TPS and T09-TPS could improve the damage of CCl4 to liver in different degree. Both the hepatoprotective and antioxidant effect of T01-TPS were better than T09-TPS. It was reasonable to suggest that TPS had remarkable protective on CCl4-induced acute liver injury and the mechanisms of protection might related to that TPS increased anti-oxidation activities.The results above indicated that T01-TPS showed better antioxidant effect than T09-TPS both in vitro and in vivo, which was possibly contributed to the difference of their structural characteristics.3 Study on hypoglycemic effect of T01-TPS and T09-TPSEffects of T01-TPS and T09-TPS on alloxan-induced diabetes mice were studied. Mouse models of diabetes were constructed by administering alloxan to mice through intraperitoneal injection. T01-TPS and T09-TPS at different dose was given to the diabetes mice by intragastric administration for 14 d, fasting blood glucose before and after treatment, body weight and the weight of immune organs were determined, at the same time, the glucose tolerance test were carried out. The results showed that both TOl-TPS and T09-TPS decreased the blood glucose level significantly in alloxan-induced mice, and showed dose-effect relation to a certain extent. The glucose tolerance test showed that T01-TPS and T09-TPS decreased the area under the curve of blood glucose significantly, which indicated that they increased the glucose tolerance in alloxan-induced mice. Furthermore, T01-TPS and T09-TPS could improve the index of thymus and spleen. It could be concluded that T01-TPS and T09-TPS had not only remarkable hypoglycemic effect but also immune-enhancing activity for diabetic mice induced by alloxan, and the effects of T01-TPS was better.