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Domestic and foreign chemical and biological activity of of tea polyphenols its Catechins systematic research on the of catechins oxidation products of a late start. Catechin conversion and formation of the oxidation product of the relationship between chemical structure and biological activity and there was little detailed study reported. The conventional view, oxidation will destroy the biological activity of the catechin oxidation product, but in recent years, research has shown that catechin oxidation product may have greater biological activity than the catechins. For further in-depth study of phenolic oxidation products to the table of the most active catechin epigallocatechin gallate (EGCG) representatives identified vitro oxidation conditions, the oxidation kinetics model, and EGCG the oxidation product of the separation, purification, identification and activity of a series of studies, the main results are as follows: EGCG in vitro determination of optimal oxidation conditions through the single factor experiment and response surface analysis, the effects of reaction temperature, oxidation time, the reaction system, the pH , oxidant EGCG quality than EGCG oxidation reaction liquid anti · OH activity, and inhibition rate indicators · OH EGCG in vitro oxidation conditions: temperature of 25 ° C, oxidation time of 15min, the reaction system pH 7.0 oxidants with EGCG quality than 1.5:1. Under this condition, the maximum the · OH inhibition rate of the oxidation reaction liquid, up to 53.40%, and more than 41.50% of EGCG · OH inhibition rate. I.e. moderately oxidized, the strongest activity of EGCG oxidation reaction liquid. 2 EGCG in vitro oxidation kinetics HPLC / MS analysis showed that mainly there are three kinds of EGCG oxidation reaction liquid oligomers oxide (EOP), and both belong to the of EGCG oxidation of dimer. Kinetic studies show that the second-order kinetics of the reaction mechanism of EGCG oxidation reaction pre-(0-10min) and EOP students. Both reaction rate decreases with increasing temperature and oxidant share of mass ratio increases accelerated; both faster reaction rate under alkaline conditions. From the optimum conditions conducive to the formation of the EOP and maintain its stable opinion, EOP generated: Temperature 25 ° C, pH 7.5, oxidant and the substrate has a mass ratio of 1.5:1, the oxidation time of 15min, with · OH inhibition rate EGCG in vitro determined as an index optimal oxidation conditions are basically the same, indicating that the main active ingredient of the EOP may be provided for the EGCG oxidation reaction liquid anti · OH. 3 EGCG fractionation its active oxidation product by extraction preliminary fractionation EGCG oxidation product fractions FRA extract obtained under neutral conditions. A containing mainly the product 1,2 and EGCG fractions FRA; extract obtained under acidic conditions. B mainly containing product 1,3, almost free of EGCG, wherein the product 1,2,3 are EGCG oxidized dimer. Antioxidant in vitro studies have shown that, Fra. A Fra. B can effectively scavenge superoxide anion, hydroxyl radical, hydrogen peroxide, and inhibition of oxidative DNA damage. Among them, Fra. A in antioxidant activity than EGCG, Fra unoxidized. The antioxidant activity of B slightly lower than EGCG. The antibacterial experiments show that the fraction Fra. A Fra. B have a strong inhibitory effect on bacteria, fungi, yeast significantly inhibited. By comparison, Fra. A Fra. The antibacterial activity of B are slightly lower than the unoxidized EGCG. 4 EGCG monomer preparation and structure of the oxidation product identification to establish the purification of the of EGCG oxidation product of monomers, preparation method, wherein fraction FRA. B by Sephadex LH-20 (40cm × 1.5cm i.d.) column chromatography eluting with 70% methanol was eluted at a flow rate 1mL/min, collecting the eluate of the main peaks available EGCG oxidation product monomer 3, concentrated , freeze-drying as a pale yellow powder; fraction FRA. C after D 101 macroporous resin (20cm × 1.0cm i.d.) desalted, eluted with 80% ethanol (natural flow rate), to collect this section eluent, ethyl acetate after extraction can be directly obtained EGCG oxidation products monomers 1, and concentrated, after freeze-drying as an orange-red powder. UV-VIS, HPLC-ESI-MS and NMR analysis, to infer the product 1 may be dehydrotheasinensin A (m / z 929), the product 3 may be for theacitrin C (m / z 911), both of the EGCG B ring between polymerization dimer formed. 5 EGCG antioxidant activity of the oxidation product of monomer further study the the of EGCG oxidation product monomer dehydrotheasinensin A tbeacitrin C in vitro antioxidant activity. The results show that in the four systems tested, dehydrotheasinensin A, and theacitrin C shows excellent antioxidant activity. Both the ability to scavenge superoxide anion EGCG 1.48-fold and 1.32-fold, respectively, scavenging ability of EGCG 1.41-fold and 1.27-fold, respectively, removal of hydrogen peroxide ability of EGCG 2.04-fold and 1.50-fold, respectively, The ability to inhibit DNA oxidative damage EGCG 2.86-fold and 2.37-fold, respectively, both far superior antioxidant activity and early separation fractions Fra. B.
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