Research On Characteristics And Activities Of Selenium-Enriched Green Tea With Different Particle Sizes

As the advantage and application of superfine comminution technology were recognized in food processing increasingly,and Se-enriched green tea possessed antioxidant and antitumor activities,in this thesis,green tea was used as selenium carrier to prepare Se-enriched green tea according to invention patent(ZL03112724.X):a kind of production regulator and direction about Se-enriched tea leaves,and then the Se-enriched green tea and regular green tea were comminuted into superfine green tea with different particle sizes by physical method.The acute toxicity was evaluated by animal experiment. Furthermore,the size effect of superfine green tea on characteristics and biological activities were investigated via TEM morphological observation,composition determination,experiments(in vitro) of adsorption of cholesterol,antioxidation and antitumor.The main results were as follows:The superfine green teas including micro-regular green tea(mRGT),micro Se-enriched green tea(mSeGT) with median size of 3.52μm and nano-regular green tea (nRGT),nano Se-enriched green tea(nSeGT) with median size of 220 nm were prepared by ball mill method that repeated twice.TEM morphological observation indicated the green tea particles were in small fractions irregularly.The tea polyphenol(TPP),amino acid and vitamin C contents of Se-enriched green tea were significantly higher than that of regular green tea.The dissolution of ingredients could be accelerated with the decrease in particle size,meanwhile,the oxidation for some labile components such as vitamin C and TPP could be accelerated.Acute toxicity test revealed that the LD₅₀ values of all the superfine green teas were more than 21.5 g/kg·bw,indicating that they were no risk of toxicity.The adsorption activities of cholesterol of superfine green teas were significantly increasing when particle size reduced from 3.52μm to 220 nm,and nSeGT exhibited the strongest adsorption capacity among all treatments.The antioxidant activity of superfine green teas was evaluated by DPPH radical scavenging and linoleic acid peroxidation inhibition methods.The antioxidant activity of superfine Se-enriched green tea was higher than regular green tea in same particle size.The DPPH radical scavenging rates of nRGT and nSeGT(67.87±0.88%and 69.49±0.54%, respectively) were significantly greater than that of mRGT and mSeGT,but the inhibition of linoleic acid peroxidation for superfine green teas of 220 nm was lower,even the nRGT exhibited prooxidation.The antitumor activity of superfine green teas was evaluated by antiproliferation assay on HepG2,A549 and MGC803 cells.The results indicated that enrichment of selenium endowed superfine green teas with higher antitumor activities on HepG2 and A549 cells but not on MGC803 cells.The inhibitory rates on HepG2,A549 and MGC803 cells achieved 77.35±5.45%,80.76±0.67%and 87.54±1.34%for nRGT,and 82.51±4.41%, 88.09±2.19%and 74.48±3.11%for nSeGT at the dose of 100μg mL^-1,which were all significantly higher compared to that of mRGT and mSeGT,and to 5-Fu.