Study Of The Extraction Kinetics Of Polyphenols In White Tea And The Targeted Sulfation And Acylation Of Catechins

White tea is one of the most representative teas in China,and catechin is its main oxidation resistant components.Up to now,the molecular modification methods of catechins mainly focus on three methods:acylation,glycosylation and methylation.But the orientation of sulfation,and the comparative study of different acylation are relatively few.Studies have-shown that metabolic pathways of catechin sulfated exist in the human body,but because of no directional sulfation,the metabolism of the research can not be in-depth.And The acylation can improve the oxidation resistance of tea polyphenols in oil system.This paper systematically analyzes the trend of the 10 active substances of 4 China representative white tea with the temperature and time,synthesises the sulfated catechin and the 5 kinds of acylated catechin by organic synthesis method.The main research contents are as follows:(1)Synthesis of the 3-sulfated(+)-catechin of by designing a reasonable reaction route.(2)Analyses of antioxidant activity of catechin and its modified products were determined by DPPH,ABTS and ORAC radical scavenging test.(3)Syntheses of 5 kinds of EGC acylated products by designing reasonable reaction routes.(4)Analyses of antioxidant activity of tea polyphenol and its EGC acylation products were determined by DPPH radical scavenging test and ?-carotene/linoleic acid system experiment.According to the above data,the variation trend of 10 active substances of four kinds of white tea was integrated with the temperature and time.The experimental datas were fitted with the Peleg kinetic model to get the low MSR(0-2.232)and high R2(0.903?0.999).And the optimized times were calculated by the Peleg's kinetic model.The optimum extraction conditions of total catechins were as follows:Fuding silver needle(43.3 min at 95 ?),Fuding white peony(32.8 min at 85 ?),Zhenghe silver needle(53.8 min at 95 ?),Zhenghe white peony(32.8min at 85 ?).The synthesis of sulfated catechin and its activity were studied,and SO3-pyridine as sulfuric acid reagent and acid-binding agent was optimized(85%yield).In DPPH and ABTS,the activity of 3-sulfate catechin was weaker than that of catechin.But In ORAC,the activity of 3-sulfate catechin was stronger than that of catechin.The syntheses of 5 acylated catechins and their activity were studied.The esterified tea polyphenols at the 3-position of C ring can be obtained by a series of reaction between EGC and decanoyl chloride,Lauroyl chloride,myristyl chloride,palmitoyl chloride or stearyl chloride.The optimum carbon chain in methanol system was 10 carbon,and in P-carotene/linoleic acid system was 14 carbon.It provided a theoretical basis for the synthesis of catechin-oriented modification products and the metabolism mechanism of catechins.