Preparation, identification, and activity evaluation of ten antioxidant peptides from protein hydrolysate of swim bladders of miiuy croaker (Miichthys miiuy)

Alcalase was screened out for hydrolyzing the swim bladder proteins of miiuy croaker (Miichthys miiuy) from five proteases using hydroxyl radical scavenging assay, and its optimal hydrolysis conditions were be determined as time 3.5 h, temperature 55 °C, pH 9.5, solid-liquid ratio 1:5, and enzyme dose 2.5%. Ten new antioxidant peptides were isolated from SMAH using ultrafiltration and consecutive chromatography, and their sequences were identified as FYKWP, FTGMD, GFEPY, YLPYA, FPPYERRQ, GFYAA, FSGLR, FPYLRH, VPDDD, and GIEWA. FPYLRH and GIEWA exhibited strong scavenging activities on hydroxyl radical (EC50 0.68 mg/mL and 0.71 mg/mL for FPYLRH and GIEWA, respectively), DPPH radical (EC50 0.51 mg/mL and 0.78 mg/mL for FPYLRH and GIEWA, respectively), and superoxide anion radical (EC50 0.34 mg/mL and 0.30 mg/mL for FPYLRH and GIEWA, respectively). In addition, FPYLRH and GIEWA could be effectively against lipid peroxidation in the β-carotene linoleic acid and in the linoleic acid emulsion system.