Antioxidant Properties of Whey Protein-Derived Peptides: Radical Scavenging and Cytoprotective Effects

Whey protein hydrolysates (WPH) are rich in peptides with potential antioxidant properties, yet the specific contributions of individual sequences remain underexplored. In this study, we identified eight antioxidant peptides-GYDTQ, GY, VY, DTDYKKY, WYS, WY, LDQW, and YW-from WPH by isolating fractions with high hydrophilic-oxygen radical absorbance capacity (H-ORAC) activity. Among them, GYDTQ was identified as a novel antioxidant peptide. The antioxidant activities of these peptides were further evaluated using 2, 2-diphenyl-1-picrylhydrazyl (DPPH) and 2, 2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging assays. All eight peptides exhibited radical scavenging activity: LDQW showed the highest H-ORAC value (3.79 ± 0.15 μmol Trolox equivalents [TE]/μmol), YW demonstrated the strongest DPPH activity (22.45% ± 1.75%), and WYS exhibited the highest ABTS activity (1.29 ± 0.06 mM TE/mM peptide). Cytoprotective assays using murine C2C12 myoblast cells revealed that DTDYKKY, GYDTQ, LDQW, and WY significantly restored cell viability under hydrogen peroxide-induced oxidative stress, with DTDYKKY showing the greatest effect. Notably, GYDTQ exhibited low radical scavenging activity but high cytoprotective potential, suggesting alternative antioxidant mechanisms. These results indicate that WPH and its constituent peptides represent potential functional foods to prevent the symptoms of oxidative stress and exercise-induced fatigue.