Structure,biological Activity And Preservation Of Plant Polyphenols

Plant polyphenols(plant tannins)are the secondary metabolites produced by plants to resist changes in the external environment and damage from pests.They are the maximum substances in plants except cellulose,hemicellulose and lignin.In recent years,plant polyphenols have been widely used in cosmetics,health care products,food and other fields.Therefore,the development and efficient application of plant polyphenol have become a research hotspot.Mangrove plants are named for their high content of plant polyphenols.In this study,R.stylosa,B.sexangula and S.apetala were selected due to their high content of total phenol(TP)and extractable condensed tannin(ECT).The value of TP extract from their leaves were respectively 288.23±2.41,325.90±1.37,408.13±2.35 mg/g(DW)when the value of ECT were respectively 173.80±6.12,268.58±5.60,244.75±3.68 mg/g(DW).We used RP-HPLC and 13C NMR to detect the structure of these polyphenols.We found that R.stylosa and S.apetala leaves' polyphenols are composed of C/EC,GC/EGC,AF/EAF while B.sexangula only have C/EC and GC/EGC.Then DPPH,ABTS,FRAP and potassium ferricyanide were used to determine their total antioxidant capacity.The results shows that these three polyphenols all have high antioxidant capacity.Then the antibacterial effects of these three polyphenols have been studied with Escherichia Coil,Salmonella typhimurium,P.Aeruginosa and Staphyloccocus aureus.In the result,all of the three polyphenols showed obvious inhibitory effect on the four bacteria,especially B.sexangula and S.apetala.Finally we have studied the antityrosinase activity and inhibitory mechanism of the three polyphenols.The result showed that the three polyphenols have strong inhibition of tyrosinase diphenylase.The value of IC50 in R.stylosa,B.sexangula and S.apetala leaves' polyphenols were respectively 0.623,0.310and 2.042 ?g/ml.As for inhibitory mechanism and nhibitory,three polyphenols are mixed type inhibitors and reversible of the enzyme.A large number of longan pericarp and seeds were wasted in the process of industrial production although it was reported that they contains high levels of polyphenols.In this study,we extracted polyphenols from leftovers of longan and did some research for their biological activities.Firstly,the value of TP from longan pericarp and seeds were respectively 39.58±3.54,69.53±1.99 mg/g(DW)when the value of ECT were 19.25±6.71,44.59±12.05 mg/g(DW)respectively Secondly,the result of DPPH and FRAP showed that the antioxidant activity of polyphenols in longan pericarp and seeds can reach more than 60%of that in fresh samples,which had good application value.The following experiment proved that polyphenols in longan pericarp and seeds could significantly inhibit the growth and reproduction of Escherichia Coil,Salmonella typhimurium,P.Aeruginosa and Staphyloccocus aureus.MIC values of longan pericarp polyphenols against all four bacteria were 3 mg/ml,MIC values of longan seeds polyphenols against Salmonella typhimurium were 3 mg/ml,and MIC values of other three bacteria were all 1.5 mg/ml.On the basis of the above research,we applied polyphenols from leftovers of logon for fresh-cut lotus root.When the concentration of polyphenols in longan pericarp and longan seeds were 2 mg/ml and 1 mg/ml respectively,compared with double distilled water,the polyphenols could inhibit browning,reduce CO2 respirtory rate and inhibit bacterial reproduction to extend the shelf life of fresh-cut lotus root effectively.In summary,the structure and biological activities of polyphenols in the leaves of R.stylosa,B.sexangula and S.apetala had been studied.This could provides some foundations and directions for the development of new plant polyphenols.We also get some theoretical basis for the efficient utilization of plant polyphenol resources with the study of leftovers of longan which had good antioxidant activity,antibactrial activity and could keep the fresh-cut lotus root edible obviously.