Isolation and characterization of three antioxidant peptides from protein hydrolysate of bluefin leatherjacket (Navodon septentrionalis) heads

• Antioxidant hydrolysate from bluefin leatherjacket head (BHH) was obtained.
• Three peptides with high antioxidant activities were isolated from BHH.
• The sequences of peptides were determined as WEGPK, GPP and GVPLT.
• The antioxidant activities of purified peptides were evaluated by five methods.

Head protein, a by-product of bluefin leatherjacket (Navodon septentrionalis) processing, was hydrolyzed by using papain, and three antioxidant peptides were prepared from the protein hydrolysate (BHH). The three peptides' sequences were determined to be Trp-Glu-Gly-Pro-Lys (WEGPK), Gly-Pro-Pro (GPP), and Gly-Val-Pro-Leu-Thr (GVPLT), with molecular weights of 615.69, 269.33, and 485.59 Da, respectively. Among the three peptides, GPP exhibited the highest scavenging activity on DPPH radicals (EC50 1.927 mg/ml), hydroxyl radicals (EC50 2.358 mg/ml), and ABTS radicals (EC50 2.472 mg/ml), but GVPLT exhibited the strongest scavenging activity on superoxide radicals (EC50 2.881 mg/ml). In addition, WEGPK could effectively inhibit the peroxidation of linoleic acid. The antioxidant activities of WEGPK, GPP, and GVPLT are due to their small molecular sizes and the hydrophobic and/or aromatic amino acid residues in their sequences. This research suggests that isolated peptides are excellent antioxidants and could be effectively applied as food ingredients, food additives and pharmaceuticals.