The purpose of this study was to determine, for the first time, antioxidant activities of seven peptides (P1-P7) derived from hydrolysis of oat proteins in a cellular model. In the oxygen radical absorbance capacity (ORAC) assay, it was found that P2 had the highest radical scavenging activity (0.67 ± 0.02 µM Trolox equivalent (TE)/µM peptide) followed by P5, P3, P6, P4, P1, and P7 whose activities were between 0.14-0.61 µM TE/µM). In the hepatic HepG2 cells, none of the peptides was cytotoxic at 20-300 µM. In addition to having the highest ORAC value, P2 was also the most protective (29% increase in cell viability) against 2,2'-azobis(2-methylpropionamidine) dihydrochloride -induced oxidative stress. P1, P6, and P7 protected at a lesser extent, with an 8%-21% increase viability of cells. The protection of cells was attributed to several factors including reduced production of intracellular reactive oxygen species, increased cellular glutathione, and increased activities of three main endogenous antioxidant enzymes.
Keywords: HepG2 cells; antioxidant enzymes; cytoprotection; oat peptides.