CHAPTER 9:Antioxidant Activity of Imidazole Dipeptides – Prevention of DNA and Protein Degradation

A previous study reported an effective method for estimating the inhibitory activities of naturally occurring antioxidants based on the degradation of target proteins by ROS. However, estimation of hydrogen peroxide was previously omitted due to its inefficiency in degrading proteins. The four major ROS types, including H2O2, ClO˙, OH˙ and ONOO˙, were employed for a novel examination of the antioxidant activities of various naturally occurring food-derived substances using DNA degradation. All ROS produced dose-dependent DNA degradation, consistent with observations using the protein degradation system. Our method enabled the determination of ROS-specific antioxidant potency. We found that the most potent antioxidant against the ClO˙ radical was a mixture of anserine– carnosine, imidazole dipeptidesisolated from chicken extract, while ferulic acidwas the most potent against the OH˙ radical, and vitamin C and the imidazole dipeptideswere the most potent against the ONOO˙ radical. For hydrogen peroxide, the imidazole dipeptidesexerted the strongest antioxidative effect examined. Finally, anserineappeared to be particularly capable of preventing DNA degradation by all four ROS examined.