Evaluation of Pure Antioxidative Capacity of Antioxidants : Esr Spectroscopy of Stable Radicals by Dpph and Abts Assays with Singular Value Decomposition

Among the antioxidant reactions, no correlation has been observed between the logarithm of the reciprocal of EC50 obtained by DPPH and ABTS assays, which can measure single electron transfer reactions. This may be owing to factors other than the radical scavenging activity. Therefore, we attempted to investigate the radical scavenging reaction of each antioxidant in DPPH and ABTS assays by directly measuring the radicals using electron spin resonance (ESR), and to study an analytical method that can eliminate other than that factor. Singular value decomposition (SVD) of the spectra that were obtained by ESR measurements was used to separate the components and to determine the detailed changes of each component. Based on the magnitude of the specific value, we focused on the first and second components, and calculated the EC50 from the changes in the spectra of the first and second components owing to the change in the antioxidant concentration in DPPH and ABTS assays to identify which component contributed more to the radical scavenging reaction. The results demonstrated a positive correlation between the EC50s of the first component of each of DPPH and ABTS assays, suggesting that the first component contributed significantly to the radical scavenging reaction of the antioxidants. Through this study, we could calculate the EC50 that significantly contributed to the radical scavenging reaction by decomposing the spectra that were obtained from ESR measurements of the reactions by DPPH and ABTS assays into specific values, that the analysis of antioxidants is possible with the desktop ESR