Individual and Synergistic Antioxidant Effects of Dipeptides in In Vitro Antioxidant Evaluation Systems

Abstract

This study aimed to investigate the individual and synergistic antioxidant effects of dipeptides in vitro. Based on a study of amino acid antioxidant activities, 36 dipeptides were chosen. All their individual antioxidant effects were tested in in vitro antioxidant evaluation systems, including the DPPH, ABTS, ORAC, and FRAP assays. Based on the results of individual antioxidant effects of these dipeptides, some of them were chosen to study their synergistic antioxidant effects in the four antioxidant assays. The results of the DPPH assay showed that dipeptides containing Cys exhibited radical scavenging activity. The synergistic antioxidant assay indicated that LC and CH, LC and CN, LC and CE, CH and CN, CH and CE, and CN and CE have significant synergistic effects (p < 0.01) in the DPPH assay. Moreover, the results of the ABTS assay showed that 17 dipeptides have ABTS radical scavenging activities and that all of them contain Cys, Trp, and Tyr residues. Their synergistic antioxidant assay showed that CR and CH, YR and YK, YR and YN, and WK and IW showed highly significant synergistic antioxidant effects (p < 0.01). The results of the ORAC assay showed that 22 dipeptides possessed ORAC activities and that all of them have one or two Cys, His, Met, Trp, and Tyr residues. The synergistic effects of CH and HL, WK and WR, YK and WR, LC and FM, FM and CH, and WK and IW were significant (p < 0.01). Finally, in the FRAP assay, six dipeptides showed ferric reducing antioxidant activities and all of them contained the Cys residue. The synergistic antioxidant effects of HV and CN, CK and CN, CH and CN, and CE and CN were also significant (p < 0.01). These findings indicate that the individual and synergistic antioxidant effects of dipeptides are related to their constituent amino acids. These results may help study other individual and synergistic antioxidant effects of dipeptides.