Abstract: In this study, the antioxidant activity of polypeptides with different molecular weights from wheat germ was investigated. Ultrafiltration and nanofiltration were used to sub-classification and purification of wheat germ peptides prepared by composite enzymatic hydrolysis. Meanwhile, oxidative damage mouse models were established and 170 mice were randomly divided into 17 groups (normal control group, model control group, wheat germ polypeptide groups with different molecular weights and different concentrations. Except the normal control group, all the mice were injected with D-galactoseat a dosage of 600 mg/(kg?d) to establish oxidative damage model. The mice in polypeptides groups were administered with polypeptides with five molecular weights at low, medium and high doses. Forty days later, the mice were sacrificed and exsanguinated from eyeballs, and superoxide dismutase (SOD) activity, glutathione peroxidase (GSH-Px) activity, malondialdehyde (MDA), and total antioxidant capacity (T-AOC) in serum and liver were determined to explore antioxidant activity of wheat germ peptides. The results showed that wheat germ peptides could improve the activities of SOD and GSH-Px as well as T-AOC in serum and liver, and reduce MDA level in serum and liver, suggesting good antioxidant activity. In addition, increasing the peptide concentration could also improve the antioxidant activity. Moreover, wheat germ peptides with molecular weight of 2000 D revealed better antioxidant activity.

Key words: wheat germ polypeptide, antioxidant activity, ultrafiltration, nanofiltration, segments, oxidative damage model