The Effect Of In Vitro Digestion On Stablity And Biological Activity Of Tea Polyphenols

Tea polyphenols have many bioactivities such as antioxidant,anticarcinogenic.However,the healthy care effects and pharmacological activities of tea polyphenols are questioned due to the poor absorption.The digestive stabilies and bioactivities of tea polyphenols are studied in vitro to evaluate the potential function of tea polyphenols in organisms,objectively and scientificly,and to give a certain theoretical guidance for better taking full advantage of bioactivies of tea polyphenols.The results are as below:1.Changes of contents and major components of tea polyphenols was studied in vitro.Results showed that the contents of tea polyphenols and catechins decreased significantly after simulated digestion.The contents of tea polyphenols were reduced by11.8%and 46.0%after simulating gastric digestion and gastrointestinal digestion,respectively,and the contents of tea catechins were respectively reduced by19.9%and91.8%.EGC increased obviously in gastric phase and GC increased significantly during gastrointestinal phase.Ester-catechins were degraded easier after simulated digestion and tea catechins were more sensitive to intestinal fluids.2.Studies on the antioxidant activities of tea polyphenols were analysed in vitro.Results indicated that the ferric-reducing antioxidant power（FRAP）,DPPH·,ABTS·⁺and·OH radical scavenging abilities were all reduced significantly after simulated digestion.And the antioxidant activities of tea polyphenols were much higher after simulated gastric digestion,but ABTS·⁺radical scavenging abilities of tea polyphenols were much higher after simulated gastrointestinal digestion.3.Influences of tea polyphenols on proliferations of E.coli and L.acidophilus were studied before and after digestion in vitro.Results showed a significant inhibitory effect on E.coli and a good promotable effect on the proliferation of L.acidophilus with concentrations of tea polyphenols.MIC₅₀ was 8.38μg/m L against E.coli of tea polyphenols.Tea polyphenols still showed a strong antibacterial effect against E.coli,but no significant promotion on the growth of L.acidophilus after simulating gastrointestinal digestion in vitro.4.Effects of food matrixes on the contents of tea polyphenols after digestion were discussed in vitro.The presence of milk,gelatinized starch and soybean oil significantly decreased the content of tea polyphenols by 21.7%,15.0%and 3.3%,respitively after simulated gastric digeation,and the content of tea polyphenols was significantly reduced by 7.7%with milk after simulating gastrointestinal digeation,compared with tea polyphenols after digestion in vitro.Others showed no influence on the content of tea polyphenols after simulated digestion.5.Effects of food matrixes on the antioxidant activities of tea polyphenols after digestion were discussed in vitro and were compared following simulated digestion.Results showed that following simulated gastric digestion the total antioxidant capacitiy and DPPH·scavenging ability of tea polyphenols was significantly reduced by the presence of milk and gelatinized starch,respectively while DPPH·scavenging ability of tea polyphenols significantly increased by adding citric acid.Additionally,ABTS·⁺scavenging ability of tea polyphenols was significantly reduced by the presence of milk,gelatinized starch,sugar and citric acid respectively after simulated gastric digestion.Moreover,following simulated gastrointestinal digestion addtion of citric acid siginificantly increased the total antioxidant capacity of tea polyphenols.The presence of soybean oil siginificantly increased DPPH·scavenging ability of tea polyphenols.Additionally,ABTS·⁺scavenging ability of tea polyphenols significantly increased by the presence of milk,gelatinized starch,soybean oil and citric acid,respectively.6.Results of the paper indicate that tea polyphenols is less sensitive to acid solution in the stomach,but vulnerable to weak alkaline solution in the intestinal.And some food matrixes can be a synergistic effects on the antioxidant activities of tea polyphenols.