Influence Of Phenolic Acids And Flavonols With Different Structures On Their Antioxidant Effects

Phenolic acid and flavonol compounds have the characteristics of wide distribution,many kinds,low toxicity and strong antioxidant activity.They can be used as prevention,intervention and treatment of chronic diseases,and improve the level of human health.The bioactivities of phenolic acids and flavones are closely related to their molecular structures.The phenolic acids and flavones with different molecular structures have different antioxidant activities.In this study,phenolic acids and flavonols were selected as the object of study.The antioxidant activities of phenolic acids and flavones were measured under three commonly used antioxidation assays(DPPH,ABTS and FRAP)in vitro.The mathematical assays of the structure parameters(o-hydroxyl,m-hydroxyl,p-hydroxy,catechol,m-methoxy,p-methoxy,steric resistance,the type of phenolic acid)and antioxidant activity of phenolic acid were established by multiple linear regression analysis.The mathematical assay between the structure parameters(p-hydroxyl base,m-hydroxyl group,methoxy group,glycoside structure)and antioxidant activity of flavonols was established,and the effects of different structural parameters of phenolic acids and flavonols on their antioxidant activity were evaluated respectively.And the contribution of different structures of phenolic acids and flavonols to antioxidation activity.Then,there may be synergetic,antagonistic or additive antioxidant effects between polyphenols in food system,which cannot be evaluated by the cumulative antioxidant activity of a single polyphenol compound in the sample.Therefore,on the basis of exploring the effect of the structure of phenolic acids and flavonols on the antioxidation activity,the influence of the structure of phenolic acid and flavonol on the antioxidation effect of the binary composite system was further studied.The effects of the structural characteristics of phenolic acids and flavonols on the antioxidant effects(synergy,antagonism and addition)of their binary combinations were systematically analyzed.The main findings are as follows:1.11 phenolic acids with representative structure were selected and their antioxidant activities in DPPH,ABTS and FRAP assays were determined.Eight different structures(o-hydroxyl group,m-hydroxyl group)of phenolic acid were established by multiple linear regression method.The relationship between antioxidation activity and p-hydroxy,catechol,meta-methoxy,para-methoxy,steric resistance,phenolic acid.The fitting degree between the experimental values and the predicted values was good(0.960?R~2?0.861),and the effects of different structures of phenolic acids on the antioxidation activity were clarified.In the DPPH and ABTS antioxidation assays,the oxidation resistance of phenolic acids with different structures was studied.In the assay of FRAP,the effect of o-hydroxyl group on the antioxidant activity of phenolic acid was the greatest,while the effect of meta-hydroxyl group on the antioxidant activity of phenolic acid was the greatest.2.Seven flavones with representative structures were selected and their antioxidant activities in DPPH,ABTS and FRAP assays were determined.Four different structural characteristics(p-hydroxyl group,m-hydroxyl group)were established by multiple linear regression method.The relationship between methoxy and glycoside structure and antioxidant activity.The fitting degree between the experimental values obtained and the predicted values is good(0.987?R~2?0.858).The effects of different structures on the antioxidant activity of flavonol were elucidated.In DPPH and FRAP assays,the main factors affecting the antioxidant activity of flavonol were m-hydroxyl structure and positively correlated with antioxidant activity.In the ABTS assay,the antioxidation activity of flavonol was positively correlated with that of metahydroxy group.The antioxidant activity of flavonol was mainly influenced by the metahydroxy structure and methoxy structure,and was negatively correlated with the antioxidant activity of flavonol.3.A binary combination of 19 phenolic acids and 7 flavonols with relatively good antioxidant activity was used to establish three antioxidation methods in vitro:FRAP,DPPH and ABTS free radical scavenging method.The antioxidant activity of the combination of phenolic acid and flavonol was determined.The relationship between the structure of phenolic acid and flavonol and the antioxidant effect(synergy,antagonism and addition)of binary composite system was studied by using the difference between experimental value and theoretical value and the rate of difference value.The results showed that the structure of phenolic acid and flavonol had a significant effect on the antioxidant effect of the binary combination.In the FRAP antioxidation assay,the cinnamic acid type or the phenolic acid with resorcinol structure showed synergistic effect.The structure of methoxy group on B ring of flavonol can enhance the synergistic effect of binary combination,while the steric structure of phenolic acid or flavonol weakens the synergetic effect of binary combination.The more the number of methoxy groups on the phenollic acid ring,the more significant the antagonistic effect was in the binary combination(p<0.05).In the antioxidation assay of DPPH,the synergetic effect of phenolic acid binary combination of p-hydroxy structure is stronger than that of para-position and stronger than that of ortho-site,and the blocking structure of phenolic acid connection site leads to the decrease of the synergistic effect of binary combination.In the anti-oxidation assay of ABTS,the structure of methoxy group on the B ring of flavonol decreased the synergistic effect of its binary combination,and the number of phenolic hydroxyl groups in phenolic acids increased from two to three,and the antagonistic effect of the binary combination on antioxidant activity was enhanced.This study provides theoretical reference for further understanding of the anti-oxidation mechanism of phenolic acids and flavones,and clarifies the contribution of phenolic acid and flavonol structures to antioxidant activity in different antioxidant assays.The rule of antioxidant effect between phenolic acids and flavonol compounds is clear,which provides theoretical guidance for the design,screening and development of efficient food antioxidants.