Purification and identification of antioxidant peptides from the skin protein hydrolysate of two marine fishes, horse mackerel (Magalaspis cordyla) and croaker (Otolithes ruber)

In the current study, two peptides with antioxidant properties were purified from skin protein hydrolysates of horse mackerel (Magalaspis cordyla) and croaker (Otolithes ruber) by consecutive chromatographic fractionations including ion exchange chromatography and gel filtration chromatography. By electron spray ionization double mass spectrometry (ESI-MS/MS), the sequence of the peptide from the skin protein hydrolysate of horse mackerel was identified to be Asn-His-Arg-Tyr-Asp-Arg (856 Da) and that of croaker to be Gly-Asn-Arg-Gly-Phe-Ala-Cys-Arg-His-Ala (1101.5 Da). The antioxidant activity of these peptides was tested by electron spin resonance (ESR) spectrometry using 1-diphenyl-2-picryl hydrazyl (DPPH center dot) and hydroxyl (OH center dot) radical scavenging assays. Both peptides exhibited higher activity against polyunsaturated fatty acid (PUFA) peroxidation than the natural antioxidant alpha-tocopherol. These results suggest that the two peptides isolated from the skin protein hydrolysates of horse mackerel and croaker are potent antioxidants and may be effectively used as food additives and as pharmaceutical agents.