The objectives of present study were to characterize the peptides which were isolated from Korean fermented soybean paste, chungkukjang, and to determine their antioxidant activities. Four fractions were collected from the methanol extract of chungkukjang by using a recycling preparative HPLC. Among fractions, Fr-2 was identified to be highly potent free radical scavenging activity in the assay of 1,1-diphenyl-2-picryl-hydrazyl (DPPH) and nitroblue tetrazolium(NBT)-reduction inhibition. Base on antioxidant effects, fraction Fr-2 was employed for the refraction with a prep-column and separated into five fractions of which two fractions were identified to have higher antioxidant activity. To confirm the amino acid constituents of antioxidant fractions Fr-2-2 and Fr-2-3 were analyzed, and eight kinds of amino acids such as aspartic acid, threonine, serine, glutamic acid, glycine, lysine, histidine, and arginine were identified as the constituent amino acids. Antioxidant activities of the separated peptides were further assessed cell viability with 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl terazolium bromide (MTT), and fluorescence-activated cell sorting (FACS) analysis of H4IIE cells treated with hydrogen peroxide (H2O2). Chungkukjang peptides have shown their ability to protect H4IIE rat hepatoma cells against H2O2- induced oxidative stress by concentration and time-dependent manner. Therefore, These results indicated that fermented soybean paste chungkukjang will be promoted the antioxidant and radical scavenging activities, and beneficial for health. The antioxidant peptide fractions Fr-2-2 and Fr-2-3 were denominated as P-NICS-1 and P-NICS-2, respectively. However, further studies were required to clarify their amino acid sequences and molecular properties, and physiological significances.
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