Determination of superoxide scavenging activity of a sample containing xanthine oxidase inhibitor by ESR spin trapping

The objective of this research was to determine the true superoxide (O-2(-) ) scavenging activity of antioxidants in a sample containing xanthine oxida se (XOD) inhibitor. A previous method involving electron spin resonance (ES R) spin-trapping has generally used 5,5-dimethyl-1-pyrroline 1-oxide (DMPO) as a spin trap and the O-2(-) generation system of hypoxanthine (HPX)-xant hine oxidase (XOD). However, this method has a problem in that the ESR sign al intensity of the DMPO spin adduct of O-2(-) (DMPO-OOH) is decreased not only by the reaction of a sample with O-2(-), but also by the inhibition of XOD. Therefore, the ESR spin-trapping method combined with the SOD additio n method was developed as a new experimental technique in this study. The r esults indicate that the O-2(-) scavenging activity of a sample containing allopurinol as an XOD inhibitor could be determined by using this method.