Identification and characterization of tilapia antioxidant peptides that protect AAPH-induced HepG2 cell oxidative stress

Nine novel peptides from tilapia hydrolysate were isolated and identified to be EKL, EKP, HKPA, ELSC, ALSC, ASLCH, SLCH, LPGYF, and LEVPGY. In addition, six fragments from in silico gastrointestinal digestion of the identified peptides, including EK, KPA, SC, CH, PGY, and EVPGY, were synthesized. The most effective parent and digested peptides showing ABTS·+ scavenging capacity were LPGYF and SC, respectively. All C- and Y-containing peptides were more effective than ascorbic acid (AsA). In contrast, K-containing peptides exhibited less antioxidant activity. All 15 peptides showed potent intracellular reactive oxygen species scavengers in the AAPH-induced HepG2 cell oxidative stress model. In addition, the digested peptides SC, CH, and PGY up-regulated the expression of CAT and SOD1 in HepG2 cells. The peptide PGY was the most effective cellular antioxidant. Thus, tilapia peptides could be potent nutraceutical products to reduce cellular oxidative stress.