Determination of Superoxide Scavenging Activity of a Sample Containing Xanthine Oxidase Inhibitor by ESR Spin Trapping

Abstract

The objective of this research was to determine the true superoxide (O₂^-) scavenging activity of antioxidants in a sample containing xanthine oxidase (XOD) inhibitor. A previous method involving electron spin resonance (ESR) spin-trapping has generally used 5,5-dimethyl-1-pyrroline 1-oxide (DMPO) as a spin trap and the O₂^- generation system of hypoxanthine (HPX)-xanthine oxidase (XOD). However, this method has a problem in that the ESR signal intensity of the DMPO spin adduct of O₂^- (DMPO-OOH) is decreased not only by the reaction of a sample with O₂^-, but also by the inhibition of XOD. Therefore, the ESR spin-trapping method combined with the SOD addition method was developed as a new experimental technique in this study. The results indicate that the O₂^- scavenging activity of a sample containing allopurinol as an XOD inhibitor could be determined by using this method.