Purification and characterization of antioxidative peptides from round scad (Decapterus maruadsi) muscle protein hydrolysate

Muscle protein from round scad (Decapterus maruadsi) was hydrolyzed with five commercial proteases, namely, Alcalase, neutral protease, papain, pepsin, and trypsin. Round scad hydrolysate (RSH) prepared with Alcalase demonstrated high antioxidative activity. After ultrafiltration, RSH-III fraction (MW < 5 kDa) exhibited the strongest activity. Then, RSH-III was purified by gel filtration chromatography (Sephadex G-15) and separated into four fractions (A, B, C, and D), of which fraction B showed the highest antioxidative activity and was further purified using reverse-phase high-performance liquid chromatography twice. The purified peptides were identified as His-Asp-His-Pro-Val-Cys (706.8 Da) and His-Glu-Lys-Val-Cys (614.7 Da) by matrix-assisted laser desorption ionization time-of-flight/time-of-flight mass spectrometry. Subsequently, the identified peptides were synthesized, and their antioxidative activities were verified. Results indicated that the two novel peptides isolated from round scad muscle protein can be developed into antioxidative ingredients in functional foods.