Isolation,Identification And Antioxidant Activity Research Of Kiwifruit Polyphenols

Kiwifruit polyphenols are complex and diverse,and there are certain difficulties in separation and purification.Thus,there are few reports on the isolation,identification and functional activity of kiwifruit polyphenolic monomer compounds.In order to further clarify the kiwifruit polyphenols and their physiological functions,and promote the rational and effective utilization of kiwifruit polyphenols,the correlation between antioxidant activity and total phenolic content of kiwifruit was discussed firstly in this study;secondly,the polyphenolic compounds in kiwifruit were separated and prepared by high-speed countercurrent chromatography coupled with preparative liquid chromatography,and the antioxidant activity of the polyphenolic monomer compounds was investigated.The main findings are as follows:(1)At 135 days after maturity(mature),the highest total phenolic content in the peel was 67.82 mgGAE/g of Miliang No.1,and the highest total phenolic content of the fruit(edible part)was 9.16 mgGAE/g of Hongyang,although the total phenolic content in Hongyang peel was lower than that of Miliang No.1 and Jinyan,but the total phenolic content of the whole fruit was equivalent to the total phenolic content of Miliang No.1 fruit,and higher than that of Jinyan;the strongest antioxidant activity of the peel was Miliang No.l,and the strongest antioxidant activity of the fruit(edible part)was Hongyang.Through the correlation between antioxidant activity and total phenolic content,there was a significant correlation respectively between the reducing power of Hongyang fruit(edible part),Jinyan fruit(edible part),Miliang No.l fruit(edible part),Jinyan peel and the total phenolic content,the correlation coefficients were 0.933,0.914,0.909 and 0.903 respectively;The ABTS+-clearing ability of Hongyang peel and Miliang No.1 peel has significant correlation respectively with its total phenolic content,the correlation coefficients were 0.900 and 0.896 respectively;There was a significant correlation between the DPPH·clearing ability and total phenolic content of the Hongyang peel,and the correlation coefficient was 0.887.In contrast,the correlation between antioxidant activity and total phenolic content of Hongyang kiwifruit is the best.Hongyang fruit has good antioxidant activity and high total phenolic content,indicating that the amount of polyphenolic compounds with antioxidant activity in Hongyang kiwifruit is high.(2)During the separation and purification of polyphenolic compounds in kiwijfruit,it was found that there were many types of polyphenolic compounds in kiwifruit,but many of them are contained in very low levels.Seven compounds were isolated from kiwifruit by high-speed countercurrent chromatography and preparative liquid chromatography.They were Neochlorogenic acid,Caffeic acid 3-O-glucoside,2-O-caffeoylthreonic acid,Epicatechin,Procyanidin C1,Malaxinic acid,Quercitrin.In addition,a compound may be presumed to be a B-type proanthocyanidin dimer.Among them,2-O-caffeoylthreonic acid and Malaxinic acid were first discovered in kiwifuit.(3)Quantitative measurement of the antioxidant activity of the prepared polyphenol monomer compound revealed that the antioxidant activity of the polyphenol monomer compound has obvious strength and weakness.The scavenging capacity of DPPH·and ABTS+.is Procyanidin C1>Epicatechin>Caffeic acid 3-O-glucoside>Mal-axinic acid;The reducing power is Procyanidin C1>Epicatechin,while Caffeic acid 3-O-glucoside and Malaxinic acid showed almost no reducing power.Among them,Procyanidin C1 and Epicatechin have strong antioxidant activity and can be used as the good source of natural antioxidants.