Antioxidant and free radical-scavenging activities of black soybean peptides (BSP)

The antioxidant and free radical-scavenging activities of black soybean peptides (BSP) fractions (Fra- I , Fra- II, Fra-III) were investigated using reducing power and DPPH-/superoxide/hydroxyl radical-scavenging assay. The reducing power activity of Fra-III was closer to that of BHT but lower than that of ascorbic acid. Fra-III showed the strongest scavenging activity against free radicals. The radical-scavenging effect was in a dose-dependent manner and the IC50 values for DPPH-, superoxide and hydroxyl radicals were found to be 1.873, 1.684 and 1.735 mg/mL, respectively. Amino acid analysis showed that Fra-I had high hydrophobic amino acids (HAA) content and hydrophobicity. The molecular weight distribution of Fra-I was found to vary from 100 to 1,000 Da mainly. The antioxidant activity of Fra-III is clearly related to the amino acid composition, the content of HAA and the molecular mass. The present study suggests that BSP with low molecular weight are useful nutritional antioxidant and potential functional factor for anti-aging