Purification and identification of antioxidant peptides from sweet potato protein hydrolysates by Alcalase

Sweet potato protein hydrolysates (SPPH) were prepared by Alcalase. The (OH)-O-center dot scavenging activity and Fe2+-chelating ability of SPPH were investigated. SPPH was further separated into four fractions by membrane ultrafiltration, and low-molecular-weight fraction F-IV (<3 kDa) exhibited the strongest (OH)-O-center dot scavenging activity and Fe2+-chelating ability, which was 59.74% and 82.27% at a concentration of 3.0 mg/mL, respectively. Fraction F-IV was then purified with size exclusion chromatography (SEC) followed by RP-HPLC, by which two fractions IV-5c and IV-5i with the highest antioxidant activities were obtained. Five peptides derived from fractions IV-5c and IV-5i were characterized by LC-MS/MS, of which Thr-Tyr-Gln-Thr-Phe, Ser-Gly-Gln-Tyr-Phe-Leu and Tyr-Met-Val-Ser-Ala-Ile-Trp-Gly matched the sequence of sporamin A, while Tyr-Tyr-Ile-Val-Ser and Tyr-Tyr-Asp-Pro-Leu matched the sequence of sporamin B. In addition, (OH)-O-center dot scavenging activities of the five peptides were determined using synthesized peptides, and Tyr-Tyr-Ile-Val-Ser showed the highest (OH)-O-center dot scavenging activity, which was 74.52% at a concentration of 1.0 mg/mL. (C) 2014 Elsevier Ltd. All rights reserved.