Purification and determination of two novel antioxidant peptides from flounder fish (Paralichthys olivaceus) using digestive proteases.

We investigated the effects of bioactive-peptides from hydrolysates of flounder fish muscle (FFM) on antioxidant activity. The hydrolysates were prepared by enzymatic reactions of FFM using eight commercial proteases such as papain, pepsin, trypsin, neutrase, alcalase, kojizyme, protamex, and α-chymotrypsin. The α-chymotrypsin hydrolysate showed the strongest antioxidant activity among the eight enzymatic hydrolysates. Further separation of the α-chymotrypsin hydrolysate was performed by ultrafiltration, gel filtration, and reverse-phase high performance liquid chromatography. Consequently, two novel peptides with high antioxidant activity were purified, and their amino acid sequences were determined (Val-Cys-Ser-Val [VCSV] and Cys-Ala-Ala-Pro [CAAP], respectively). The two peptides showed good scavenging activity against the 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical (IC(50) values, 111.32 and 26.89 μM, respectively) and high cytoprotective activities against 2,2-azobis-(2-amidino-propane) dihydrochloride (AAPH) without cytotoxicity and scavenged total reactive oxygen species in Vero cells. In particular, apoptotic bodies produced by AAPH dose-dependently decreased following treatment with the CAAP peptide. These results revealed firstly the two peptides with strong antioxidative effects from FFM.