Structural Characterization,Antioxidant Activity And Inhibition Of Nonenzyme Glycosylation By Maleic Anhydride Modified Tea Polyphenols

In this paper,tea polyphenols(TP)was modifies with maleic anhydride as modifier under the optimized conditions.The structure of maleic anhydride modified tea polyphenols(MA-TP)prepared under the optimal conditions was characterized.Three chemical methods were used to comprehensively evaluate the antioxidant capacity of MA-TP,and the simulation system of Fru-Lys and vinegar non-enzymatic glycation were established to explore the inhibitory effect of the prepared MA-TP on non-enzymatic glycation reaction,so as to elucidate the theoretical and experimental basis for the application of MA-TP in food processing.The main results of this study are as follows:(1)The preparation of MA-TP.The effects of the ratio of raw materials,reaction temperature and reaction time on the esterification rate of TP were investigated by single factor experiment and orthogonal experiment,and the structure of MA-TP prepared under the optimal conditions was characterized.The results showed that the highest esterification rate of TP was 21.17?0.02% at the ratio of 1:4,reaction temperature 50? and reaction time 6 h.The absorption peaks of C=O,C-O-C and C=C in MA-TP spectra were obviously enhanced.The NMR spectra of MA-TP shows the hydrogen proton peak disappeared and new proton peak and C peak appeared.The contents of C and H in MA-TP were found in good agreement with the theoretical values of C and H contents calculated based on the mono-substituted products of TP with the errors less than 0.2%.At the same time,the thermal stability analysis shows that MA-TP has stronger thermal stability and is not easy to thermal decomposition.(2)Three chemical methods,including DPPH,ABTS and FRAP were used to comprehensively determine the antioxidant activity of MA-TP;In the Fru-Lys non-enzymatic glycosylation simulation system,amino guanidine(AG)was used as a positive control,GO,MGO,3-DG,5-hydroxymethyl furfural,pentosidine and fluorescent AGEs of each group of the sample solutions were detected.The results show that in the concentration range of 20?100 ?g/m L,the scavenging ability of MA-TP against DPPH,ABTS free radicals and the reducing ability of iron ions were found lower than that of TP(p<0.05),while MA-TP show higher anti-glycation ability than TP and AG;M MA-TP can significantly inhibit the production of products in each stage of the reaction system(p<0.05),indicating that MA-TP has a good inhibitory effect on non-enzymatic glycosylation reaction(3)Non-enzymatic glycosylation reaction systems were simulated with six vinegars:white vinegar,rice vinegar,balsamic vinegar,mature vinegar,apple cider vinegar and grapefruit vinegar,and Vc was used as the positive control.The changes of reducing sugar,soluble protein,color rate and non-enzymatic glycosylation product fluorescent AGEs,three dicarbonyl compounds and 5-HMF content of different kinds of vinegar during heating reaction were detected.For grapefruit vinegar,the correlation of 5-HMF content changes with dicarbonyl compounds,reducing sugar and soluble protein was analyzed.The results showed that the contents of phenol,reducing sugar and protein in the reaction groups of TP,MA-TP and Vc in the vinegar simulation system decreased slowly,and the changes of the basic components in the MA-TP group were the least.,The color rate of vinegar and non-enzymatic glycosylation products were found to be inhibited and MA-TP show the strongest effect.In addition,TP and MA-TP were also found to inhibit the turbidity of vinegar in the heating reaction of grapefruit vinegar.The formation of 5-HMF was found significantly related to the change of dicarbonyl compounds,and 3-DG may be an intermediate product of 5-HMF formation in vinegar.