Novel antioxidant peptides from sheep plasma protein hydrolysates: Purification, identification and cytoprotective effects against H2O2‐induced oxidative stress

Abstract This study sought to purify and identify antioxidant peptides from sheep ( Ovis aries ) plasma protein hydrolysates and assess their protective impacts on H 2 O 2 ‐induced Caco‐2 cells. The purification process involved reversed high‐performance liquid chromatography, anion‐exchange chromatography, and Sephadex G‐25. Three peptides, namely Trp‐Glu‐Glu‐Pro‐Ala‐Met (WEEPAM), Ser‐Leu‐His‐Phe‐Met‐Glu (SLHFME), and His‐Cys‐Thr‐Thr‐Phe‐Met‐Ile, with molecular weights of 761.84, 762.87, and 852.03 Da, respectively, were identified by liquid chromatography with tandem mass spectrometry. Among the three antioxidant peptides, superoxide radical (O 2 − ) radical scavenging capacity of WEEPAM and SLHFME was not significantly different from glutathione (GSH) ( p > 0.05), while their 1,1‐diphenyl‐2‐picrylhydrazyl radical scavenging capacity was greater than GSH ( p < 0.05). WEEPAM revealed increased antioxidant activity after pepsin and trypsin hydrolysis under an in vitro digestion model. In addition, WEEPAM inhibited oxidative damage in Caco‐2 cells by significantly reducing reactive oxygen species accumulation, early apoptosis, malondialdehyde formation, and increasing intracellular superoxide dismutase, glutathione peroxidase, and catalase activities.