ANTIOXIDATIVE PROPERTIES OF HISTIDINE-CONTAINING PEPTIDES DESIGNED FROM PEPTIDE-FRAGMENTS FOUND IN THE DIGESTS OF A SOYBEAN PROTEIN

The properties of 22 synthetic peptides containing histidine, which we re designed on the basis of the antioxidative peptide (Leu-Leu-Pro-His -His) derived from proteolytic digests of a soybean protein, were exam ined with regard to their antioxidative activity against the peroxidat ion of linoleic acid and the scavenging effects on active oxygen and f ree radical species. The antioxidative activities of these peptides in an emulsion oxidation system using 2,2'-azobis(2-amidinopropane) dihy drochloride as a radical initiator correlated well within an aqueous s ystem. Although the histidine-containing peptides had a quenching acti vity on singlet oxygen, they did not show antioxidative activity in an 2,2'-azobis(2,4-dimethylvaleronitrile)-induced oxidation system or sc avenging effects on 1,1-diphenyl-2-picrylhydrazyl radical and superoxi de. The metal-ion chelating activities and the hydrophobicities of the se peptides showed no direct correlation with their antioxidative acti vities. Leu-Leu-Pro-His-His was modified with a hydroxyl radical in an aqueous ethanol system during the peroxidation of linoleic acid.