Nitroimidazole and oxygen derived radicals detected by electron spin resonance in hydrogenosomal and cytosolic fractions from Trichomonas vaginalis.

Hydrogenosome-enriched fractions from Trichomonas vaginalis reduce a number of nitroimidazole derivatives to their respective electron spin resonance-detectable nitro-anion radicals. In the presence of of oxygen and 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) a superoxide spin trapped adduct of DMPO was formed; the rate-determining step was the prior formation of the nitro-anion radical. Oxygen-derived radicals were detected with cytosolic fractions from a metronidazole-resistant isolate (CDC-85) when incubated with NADH or NADPH as respiratory substrate. The requirement for superoxide dismutase and catalase to completely abolish formation of these signals suggests contributions from both superoxide and peroxide. No oxygen-derived radicals were observed with cytosolic fractions from a metronidazole-susceptible strain (C1-NIH).