Purification and characterization of three antioxidant peptides from protein hydrolysate of grass carp (Ctenopharyngodon idella) skin

• Antioxidant hydrolysate (GPH) from grass carp skin was obtained.
• Three peptides with high antioxidant activities were isolated from GPH.
• The antioxidant peptides had high radical scavenging activity.
• The activities of peptides were due to smaller size and hydrophobic amino acids.

Protein derived from grass carp (Ctenopharyngodon idella) skin was hydrolyzed by using Alcalase to obtain antioxidant peptides. Three antioxidant peptides were isolated from the protein hydrolysate and their amino acid sequences were determined to be Pro-Tyr-Ser-Phe-Lys (640.74 Da), Gly-Phe-Gly-Pro-Glu-Leu (618.89 Da) and Val-Gly-Gly-Arg-Pro (484.56 Da). The three purified peptides exhibited high scavenging activity on DPPH radical (IC50 2.459, 3.634 and 6.063 mM, respectively), hydroxyl radical (IC50 3.563, 2.606 and 4.241 mM, respectively) and ABTS radical (IC50 0.281, 0.530 and 0.960 mM, respectively) in a dose-dependent manner. In addition, all peptides also effectively inhibited the peroxidation in linoleic acid model system. The high activity of purified peptides was attributed to the small sizes and the peculiar amino acid residues within their peptide sequences. Results indicated that the novel peptides isolated from grass carp skin possess potent antioxidant activities and might be used for food preservation and medicinal purposes. However, more detailed studies are required to explore their antioxidant abilities in vivo.