改性果胶与白藜芦醇的相互作用机制及抗氧化能力

Investigation into Interaction Mechanism and Antioxidant Activity of Resveratrol and Modified Pectin

白藜芦醇是一种具有生物活性的芪类化合物,在紫外光照射或高温加热时其结构会被破坏,从而削弱其生物活性。果胶能够与白藜芦醇发生非共价结合,有利于保护白藜芦醇的生物活性。文中采用酶解–超声耦合方法改造果胶结构,对改性后果胶的分子结构与形貌变化进行了表征,并采用等温滴定量热法探讨了果胶与白藜芦醇的相互作用机制,讨论了果胶-白藜芦醇复合物经紫外光照射或加热后抗氧化能力的变化。结果表明,酶解协同超声处理可有效降低果胶的相对分子质量和酯化度,经45 min酶解后加超声处理的果胶(PE45U)的重均相对分子质量仅为原果胶的2%。由扫描电镜图可以看出,改性果胶表现出更多不规整的“片段化”结构。酶解-超声耦合改性能够暴露出更多果胶分子内的—OH,大幅增加果胶与白藜芦醇之间的结合位点,提升两者之间的亲和性,PE45U与白藜芦醇的结合位点是原果胶与白藜芦醇结合位点数的24倍。改性果胶与白藜芦醇相互作用后能够显著增强白藜芦醇经紫外光照射或加热后的抗氧化能力(P<0.05),这为解决白藜芦醇等芪类功能成分在食品应用中光稳定性和热稳定性差的问题提供了新思路。

Resveratrol(RES)is a kind of stilbene compound with bioactivities and ultraviolet or heating treatment can weaken its bioactivities by destroying its structure.Pectin is able to form non-covalent bonds with RES,which is conducive to the protection of antioxidant activity of RES.In this study,the structure of pectin was modified by the method of enzymolysis combined with ultrasound treatment.The molecular and microscopic structure of modified pectin was characterized,and the interaction mechanism between pectin and RES was discussed by isothermal titration method.At last,the antioxidant activity of RES-pectin complex under ultraviolet or heating treatment was tested.The results show that enzymolysis combined with ultrasound modification method can remarkably reduce the relative molecular mass and degree of methyl esterification(DM)of pectin.The weight-average molecular mass of pectin(PE45U)modificated by 45-min enzymolysis and ultrasound treatment is only 2%of that of unmodified pectin.SEM images show more irregular fragments of pectin structure after the modification.The enzymolysis-ultrasound modification exposes a great number of—OH of pectin,which considerably increases the interaction sites and affinity between RES and pectin.The interaction sites number between PE45U and RES is 24 times that between unmodified pectin and RES.The antioxidant activity of RES is significantly enhanced after interacting with pectin under ultraviolet or heating treatment(P<0.05).This study provides new insights to solve the problem of poor ultraviolet and thermal stability of RES and other stilbene in food industry.