Abstract
Antioxidative activities of various dipeptides on linoleic acid were investigated. Nine dipeptides consisting of L-alanine as N-terminal amino acid showed more effective antioxidative activities than those of amino acid mixtures which constitute dipeptides. Especially, Ala-His, Ala-Met, Ala-Ty and Ala-Try prolonged the induction periods to two times longer than those of corres- ponding amino acids.
Among 17 dipeptides consisted of L-tyrosine, L-histidine and L-methionine as N-terminal amino acid, although L-histidine in dipeptides showed less antioxidative activities as compared to those of corresponding amino mixtures, L-tyrosine and L-methionine in dipeptides showed more antioxidative activities than those of amino acid mixtures with exception of Met-Pro and Met-Met.
Antioxidative activity of dipeptide varied with the position of amino acid in peptide. That is, dipeptides consisting of L-tryptophan and L-tyrosine as N-terminal amino acid showed more inhibitive activities on oxidation of linoleic acid than those of dipeptides consisting of respective amino acids as C-terminal. On the contrary, L-methionine and L-histidine in dipeptide as C-terminal amino acid showed stronger antioxidative activities.
Synergistic effect was recognized in combination of dipeptide with d-tocopherol and that effect was similar to that of amino acid.
