ANTI-FATIGUE AND ANTIOXIDATIVE ACTIVITIES OF PEPTIDES ISOLATED FROM MILK PROTEINS

Abstract

Milk proteins were hydrolyzed with chymotrypsin and trypsin. Effects of hydrolysis conditions were studied through L9 (34) orthogonal experiment, and optimization hydrolysis conditions (substrate concentration, 25% (w/v); hydrolysis temperature, 45C; hydrolysis pH, 8.0; hydrolysis time, 2 h) were obtained. Six peptide fractions were separated from hydrolyzates by ultra-filtration and sephadex G-15 gel filtration chromatography. Anti-fatigue activity (swimming endurance tests) of each fraction was determined. Fraction 3 (F3) possessed longest swimming time. The anti-fatigue activity of the F3 peptide was evaluated. Loaded swimming time, serum blood urea nitrogen (SBUN), blood lactic acid and hepatic glycogen of mice were determined. F3 peptide can significantly increase the loaded swimming time and hepatic glycogen of mice, and decrease SBUN and blood lactic acid after swimming of mice. The antioxidant activity of the F3 peptide was also evaluated. F3 peptide had capacity to scavenge hydroxyl radical and superoxide anion radical. PRACTICAL APPLICATIONS Milk protein has been widely used as a material for peptides production by enzymatic hydrolysis. However, few anti-fatigue peptides from milk protein were reported. This work was found that the peptides hydrolyzed from milk protein had both anti-fatigue and antioxidant activities. It is to be expected that milk protein-derived anti-fatigue and antioxidant activity peptides would have no undesirable side-effects. As a consequence, the milk protein hydrolyzates with anti-fatigue and antioxidant activity could be applied in functional foods or beverages designed for persons suffering from diseases caused by fatigue, reactive oxygen species (ROS) and free radicals.