Scavenging of superoxide anion radical by chaparral

Chaparral is considered to act as an antioxidant. However, the inhibitory e ffects of chaparral on specific radical species are not well understood. Us ing electron paramagnetic resonance (EPR) spectroscopy in combination with spin trapping techniques, we have found that chaparral scavenges superoxide anion radical (O-2(.-)) in a dose-dependent manner. 5,5-dimethyl-lpyrrolin e-N-oxide (DMPO) was used as a spin trapping agent and the reaction of xant hine and xanthine oxidase as a source of O-2(.-). The kinetic parameters, I C50 and V-max, for chaparral scavenging of O-2(.-) were found to be 0.899 m u g/mL and 8.4 ng/mL/sec, respectively. The rate constant for chaparral sca venging O-2(.-) was found to be 1.22 x 10(6) g(-1) s(-1). Our studies sugge st that the antioxidant properties of chaparral may involve a direct scaven ging effect of the primary oxygen radical, O-2(.-).