Analysis Of Antioxidant Mechanism Of Teas Based On Multivariate Analysis

In this study,the multivariate analysis was used to explore the correlation between the antioxidant activity of tea and the difference of active substances,and to analyze the mechanism of antioxidant activity of tea based on the systematic analysis of the differences in the antioxidant activities of six major types of tea and the types of active substances.The main research contents were as follows:1.Different types of tea were evaluated by six different antioxidant experiments(DPPH free radical scavenging ability,FRAP total antioxidant capacity,ABTS free radical scavenging ability,total reducing ability,cell antioxidant capacity and detection active oxygen in cell by flow cytometry).The results of chemical experiments in vitro and cellular antioxidant experiments in vivo showed that the antioxidant capacity of tea was weakened according to green tea,yellow tea and white tea,oolong tea,black tea and black tea.It was meaning that the antioxidant capacity of tea decreased with the degree of fermentation.The results also showed that the antioxidant capacity of green tea was stronger than that of black tea by about 9 times.Because of the differences in the origin,variety and tenderness of fresh leaf and the processing of tea,There was a difference among different types of tea and the same type of tea.There was a significant difference in antioxidant capacity among different types of tea.2.Six types of tea(green tea,oolong tea,white tea,yellow tea,black tea and black tea)were extracted and prepared by alcohol extraction.UPLC-Q-TOF was used to detect tea samples and identified active compounds in different types of tea.There were 65 bioactivity compounds obtained: 4 alkaloids and amino acids,11 catechins,10 catechin polymers,4 catechin oxides,12 phenolic acids and 24 flavonoids.Comparing the types and contents of the compounds in different types of tea,the types and contents of the compounds in green tea were the highest,and the types and contents of the compounds in black tea and black tea were all reduced.With varying degrees of oxidation,the physiologically active substances in the tea leaves were reduced or even not detected by the oxidation process.3.By comparing the differences in zinc and selenium contents among the six types of tea,there was a small difference in zinc content among green tea,white tea,yellow tea,black tea and black tea.But the content of zinc in oolong tea was lower than that of the other five types of tea.The difference of selenium content in six types of tea was small,while the difference in selenium content in the same type of tea is significant.Pearson correlation analysis was used to explain the relationship between the content of zinc and selenium in teas.The results showed that there was a significantly negatively correlated between zinc and selenium contents in tea.4.Correlation analysis showed that there was a significant positive correlation between antioxidant indices.There was a significant positive correlation between total phenols and total flavonoids content and antioxidant capacity of tea.The principal component analysis and cluster analysis showed that there were significant differences among different types of tea except for white tea and the similarity among the same types of tea was very high.According to least squares regression method and path analysis,theanine,theophylline,EGC,EGCG,(-)-epiafzelechin gallate,procyanidin dimer,4-galloylquinic acid,5-caffeoyloylquinic acid,3-galloylquinic acid,GCG,ECG,CG,5-galloylquinic acid,dihydrokaempferol had a significant effect on the antioxidant capacity of tea.The alkaloid content was positively correlated with the zinc content in tea,while quercetin-3-O-galactosyl rutin was significantly positively correlated with selenium content.