Abstract: In this experiment, HEK293 cells were induced by H2O2 to establish a cell model of oxidative damage, and the optimal H2O2 concentration and treatment time were determined. The effects of five antioxidant peptides (AFK, IEQI, FPFF, LPVPQ and RELEEL) derived from yak milk casein on the survival rate, malondialdehyde (MDA) content, antioxidant enzyme activities, reduced glutathione and oxidized glutathione contents of the damaged cells were studied, and the mechanism of action of the antioxidant peptides was explored to provide a theoretical basis for their development and application in high value-added biological products and functional foods. The results showed that these antioxidant peptides had different scavenging effects on different radical species, but they all showed a dose-effect relationship. After being treated with a final concentration of 400 μmol/L H2O2 for 12 h, the inhibitory rate of HEK293 cells was (46.21 ± 0.40)%. Cytotoxicity test showed that the five antioxidant peptides had no toxic or side effects on HEK-293 cells, and did not promote cell proliferation either. These antioxidant peptides could significantly reduce the contents of malondialdehyde (except LPVPQ) and oxidized glutathione in HEK293 cells damaged by oxidation, and enhance the activity of antioxidant enzymes. RELEEL at a concentration of 200 μg/mL significantly reduced MDA content to (0.062 ± 0.000) nmol/104 cells and increased glutathione content to (61.17 ± 2.48) μg/106 cells while maintaining high GSH/GSSG ratio of 64.93 ± 0.95. The antioxidant peptide LPVPQ at 200 μg/mL significantly reduced the content of oxidized glutathione to (0.74 ± 0.26) μg/106 cells and increased the activity of superoxide dismutase (SOD) to (1.17 ± 0.02) U/104 cells; the antioxidant peptide AFK at 200 μg/mL significantly enhanced catalase (CAT) activity to (0.60 ± 0.09) U/104 cells. These results indicate that the antioxidant peptides derived from yak milk casein have positive effects on cells damaged by oxidation, which can provide a reference for further development of relevant products.

Key words: yak milk casein; antioxidant peptides; HEK293 cells; oxidative damage; protective effect