Study On The Interaction Mechanism Between Modified Pectin And Resveratrol And Its Bioactivities

Polysaccharides and polyphenols are two important components in food,and they have distinctly different functional properties.The interaction between food components is a key factor that determines the physicochemical properties and nutritional properties of food.The interaction between food components can achieve physicochemical properties and functional properties that cannot be achieved by a single component,providing new ideas for the design of structure of foods.Resveratrol has many physiological activities which are beneficial to human health,such as anti-inflammatory,anti-oxidant,anti-tumor,and anti-cardiovascular diseases.However,the poor light stability and thermal stability of resveratrol restrict its application in food.In order to enhance the bioavailability of resveratrol,the interaction with other substances can be used to improve the stability of resveratrol.This research takes pectin and resveratrol as the objects and studies the interaction of different modified pectins and resveratrol.In this research the interaction mechanism between pectin and resveratrol as well as the effect of the interaction on the antioxidant activity,anti-inflammatory activity and storage stability of resveratrol were explored.The main findings are as follows:(1)Taking pectin as the research object,the effects of three modification methods,including enzymatic treatments,ultrasonic treatments and ultrasound-assisted enzymatic treatments,on its structure and performance were discussed.Enzymatic treatments can significantly reduce the molecular weight(Mw)of pectin molecules,and ultrasonic treatments can effectively reduce the molecular weight and DM of pectin,but the effects of ultrasound and pectinase did not affect the acetyl group in the pectin structure.The enzymatic and ultrasonic treatment can significantly reduce the Mw and DM of pectin,while keeping its DAc constant.NMR results showed that the pectinase and ultrasound did not change the configuration and bonding mode of pectin.SEM images showed more irregular fragments of pectin structure after modification.(2)The interaction mechanism between pectin and resveratrol was explored by using fluorescence quenching kinetics and isothermal titration calorimetry(ITC).By the method of kinetics and thermodynamics,this study explored the effect of different modification methods on pectin-resveratrol interaction.Pectin,enzymatically modified pectin and ultrasound-assisted enzymatically modified pectin have strong fluorescence quenching effect on resveratrol,and the quenching rates are 13.75%,15.74%and 14.74%,respectively.The quenching mechanism of pectin/modified pectins on resveratrol was mainly static quenching caused by the formation of a non-luminescent complex between pectin/modified pectins and resveratrol.At 300 K,the binding constants K_A of the pectin/two modified pectins and resveratrol in descending order were:enzymatic ultrasound-assisted enzymatically modified pectin>enzymatically modified pectin>pectin,indicating the binding strength between ultrasound-assisted enzymatically modified pectin and resveratrol was the strongest.Resveratrol was mainly combined with pectin and two kinds of modified pectins through van der Waals forces or hydrogen bonds.ITC results showed that the interactions between the pectin/two modified pectins and resveratrol were all spontaneous thermal reactions,and the modification can greatly enhance the affinity of pectin and resveratrol.(3)The antioxidant and anti-inflammatory activities of the pectin/modified pectin-resveratrol complexes were evaluated by chemical methods and cell model methods.Using chemical methods to determine the anti-oxidation properties of the compound,it was found that the ability of the three modified pectin-resveratrol complexes to scavenge ABTS⁺,DPPH,superoxide anion and hydroxyl free radicals was significantly stronger than that of the pectin-resveratrol complex(p<0.05).Compared with resveratrol and pectin,the three modified pectin-resveratrol complexes had significantly improved ability to scavenge ABTS⁺·,DPPH·and·O₂^-(p<0.001),while the ability to scavenge·OH^-decreased(p<0.05).The results of MTT assay showed that pectin,three modified pectins,resveratrol and their complexes were non-toxic to RAW 264.7 cells.Different biochemical indicators(including T-AOC,SOD,MDA,CAT,and GSH-Px)of H₂O₂-stimulated RAW 264.7 cells were measured,and the results showed that the pectin/modified pectin-resveratrol complexes can significantly increase the activities of T-AOC,SOD,CAT and GSH-Px in RAW 264.7 cells,and reduce MDA content(p<0.05).Compared with resveratrol,the three modified pectin-resveratrol complexes had stronger inhibitory effects on NO and ROS in RAW 264.7 cells(p<0.05).Meanwhile,the interaction between the three modified pectins and resveratrol can significantly enhance the inhibitory effect of resveratrol on the level of TNF-?,IFN-?and IL-6 m RNA in LPS-induced RAW 264.7cells(p<0.05).The results showed that the interaction between resveratrol and modified pectins can significantly enhance its antioxidant and anti-inflammatory capabilities.(4)The influence of the interaction between different modified pectins and resveratrol on the light/thermal stability of resveratrol was evaluated.Compared with resveratrol and the pectin-resveratrol complex,the interaction of resveratrol and three modified pectins can significantly improve its in vitro antioxidant capacity after heating.Within 2.5 hours of 254 nm ultraviolet light irradiation,the scavenging abilities of the three modified pectin-resveratrol complexes on four free radicals were significantly stronger than that of resveratrol(p<0.05),and the ultrasound-assisted enzymatically modified pectin-resveratrol complexes showed the best stability.After resveratrol was compounded with pectin/modified pectins,they still had a high scavenging ability for four free radicals after being exposed to 365 nm ultraviolet light for2.5 hours,and they were significantly higher than resveratrol(p<0.05).Among them,the three modified pectin-resveratrol complexes were significantly stronger than the pectin-resveratrol complex(p<0.05).The interaction between modified pectins and resveratrol can enhance the antioxidant and anti-inflammatory activities of resveratrol.At the same time,the modified pectins can protect the structure of resveratrol under heating and ultraviolet light conditions,thereby protecting the anti-oxidation ability of resveratrol.This study provided a new idea for the improvement of antioxidant and anti-inflammatory activity and protection of photostability and thermal stability of resveratrol and other stilbene functional ingredients in the application of food ingredients.