Antioxidant properties of fractions isolated from blue shark (Prionace glauca) skin gelatin hydrolysates

Antioxidative fractions were isolated from hydrolyzed blue shark skin gelatin with Protamex, and the DPPH and hydroxyl radical scavenging abilities were investigated. The IC50 values of hydrolysates to scavenge DPPH and hydroxyl radical signals were 13.30 and 4.30 mg/mL, respectively. Three fractions (I, II, III) were obtained after separated by Sephadex G-15 gel filtration. The IC50 values of fraction III to scavenge DPPH and hydroxyl radical signals were 0.57 and 2.04 mg/mL, respectively, which were close to glutathione. It was found that fraction III was mainly composed of four peptides and four amino acids by RP-HPLC and ESI-MS/MS analysis, including Glu-Gly-Pro, Gly-Pro-Arg, Gly-Tyr, Gly-Phe, Leu, Arg, Tyr and Phe. The activity assessments for these components indicated that the dipeptide of Gly-Tyr and amino acid of Tyr were important for the excellent antioxidant activities. It is concluded that fraction III has a great potential as natural functional materials for supplement.