Study on Antioxidant Activity of Walnut Polypeptide and Its Molecular Weight,Amino Acid Composition Characteristic

Objective:In order to improve the utilization value of walnut dregs and elucidate the antioxidant activity of walnut peptides and its structure-activity relationship. Methods:DA 201-C macroporous resin and Sephadex G-15 glucan gel were used to isolate and purify the enzymatic hydrolysis of walnut dregs protein by complex protease. The antioxidant activity and amino acid composition of walnut peptides with different hydrophobicities and molecular weights were analyzed and composed. Results:The antioxidant activities of polypeptide fractions I,II and III,which were separated by DA 201-C macroporous resin,increased with the increasing of the eluent hydrophobicity. Four different molecular weight polypeptide components of a,b,c,d were isolated and purified from component III by Sephadex G-15. Component c,which was similar to component III in amino acid composition,had the highest hydroxyl radical scavenging capacity and contained higher glutamate,aspartate,leucine and phenylalanine. Its molecular weight was distributed in 400~700 Da. Conclusion:Walnut polypeptide with better antioxidant activity had a molecular weight of less than 800 Da,it had the characteristics of strong hydrophobicity and relatively high composition contents of glutamic acid,aspartic acid,leucine and phenylalanine.