Abstract: On the basis of protein content, amino acid composition and molecular weight distribution of corn oligopeptides (COP), the antioxidant activity of COP in vitro was evaluated by determining the abilities to scavenge DPPH, hydroxyl and superoxide anion free radicals as well as reducing power. Results indicated that the content of total protein was 89.28%, of which acid soluble proteins accounted for 94.31%; amino acid composition was unique and COP was rich in amino acids such as leucine, proline and alanine with strong antioxidant activity. The major molecular weight of COP was less than 1000 (93.05%), and small peptides with a molecular weight range of 132－576 were dominant. The median inhibitory concentrations (IC50 values) of COP for scavenging DPPH, hydroxyl and superoxide anion free radicals on the basis of scavenging rate were 1.9, 5.4 mg/mL and 14.9 mg/mL, respectively. The reducing power of COP at a concentration of 5.0 mg/mL was similar to that of ascorbic acid at 0.02 mg/mL. The antioxidant activity of COP exhibited a dose-dependent relationship.

Key words: corn, oligopeptide, molecular weight distribution, amino acid composition, antioxidant activity