Antioxidant Effect of Egg Yolk Peptides against Tert-butyl Hydroperoxide Induced Oxidative Stress in Caco-2 Colon Cancer Cells

Oxidative stress can damage lipids, proteins and DNA. The effect of hydrolysed, purified defatted egg yolk protein by-product (fraction EYGF-23) on oxidative stress in Caco-2 colon cancer epithelial cells was investigated for the first time. Caco-2 cells exposed to toxic 3 mM tert-butyl hydroperoxide (t-BHP) for 2 hours were protected when pretreated with 1.0 mg/ml EYGF-23 for 24 hours. The peptides inhibited intracellular reactive oxygen species (ROS) (60.0%) and malondialdehyde (MDA) (24.2 µg/ml) production, compared to cells treated with only t-BHP (75.3% and 32.2 µg/ml respectively). EYGF-23 inhibited caspase 3/7 activity in stressed cells, thereby protecting cells from induced caspase-dependent apoptosis. Further, total glutathione level and superoxide dismutase activity were significantly elevated to 0.29 µM and 55.10% respectively, in cells pretreated with EYGF-23, compared to t-BHP treatment alone (0.10 µM and 44.22 % respectively). Peptides WYGPD, TMFPSA and WIHNENQGF and hydrophobic amino acids tyrosine (Y) and tryptophan (W) contributed to cellular antioxidant activity against oxidative stress in colon epithelial cells and may have nutraceutical applications.