Preparation and anti-oxidative effects of corn peptides

Corn peptides(CP) were prepared from zein via proteolysis by means of a type of alkaline protease, Alcalase. at 50 degreesC and pH 8.0. The anti-oxidative activity of the hydrolysate was examined. It was found that the anti-oxidative activity reached the maximum at the fourth hour of the hydrolysis and then decreased. The effect of the enzyme dosage on the solubility of corn protein, the dependence of hydrolysis time on the degree of the hydrolysis (DH) and molecular weight distribution were examined respectively. 30% DH was controlled on the basis of anti-oxidative activity. The hydrolysate was fractionated on a Sephadex G-15 column. The anti-oxidative activities were examined for all the fractions. The main fraction for anti-oxidative activity was collected and, characterized by the methods of amino acid analysis, the measurement of average chain length and etc.. The main M-W. distribution of the main fraction was 300-600 Daltons. The anti-oxidative properties of the small peptides in vitro were studied. It was found that they could inhibit the auto-oxidation of pyrogallol and the oxidation of hemoglobin. The hemolysis degree of erythrocyte caused by hydroxyl free radicals was decreased greatly, indicating a protective effect of the anti-oxidative peptides on the cell membrane damage of erythrocyte.