Purification and Identification of Antioxidant Peptides from Enzymatic Hydrolysate of Spirulina platensis

The aim of this study was to isolate antioxidant peptides from an enzymatic hydrolysate of Spirulina platensis. A novel antioxidant peptide was obtained by ultrafiltration, gel filtration chromatography, and reverse-phase high-performance liquid chromatography, with the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging assay used to measure the antioxidant activity, and the sequence was determined to be Pro-Asn-Asn (343.15 Da) by electrospray ionization tandem mass spectrometry. This peptide was synthesized to confirm its antioxidant properties, and it exhibited 81.44 +/- 0.43% DPPH scavenging activity at 100 mu g/ml, which was similar to that of glutathione (82.63 +/- 0.56%). Furthermore, the superoxide anion and hydroxyl free-radical scavenging activities and the SOD activity of the peptide were 47.84 +/- 0.49%, 54.01 +/- 0.82%, and 12.55 +/- 0.75%, respectively, at 10 mg/ml. These results indicate that S. platensis is a good source of antioxidant peptides, and that its hydrolysate may have important applications in the pharmaceutical and food industries.