Microsomal reduction of gentian violet. Evidence for cytochrome P-450-catalyzed free radical formation

The triarylmethane dye, gentian violet, is shown to undergo a one-electron reduction by the cytochrome P-450 monooxygenase system to produce a carbon-centered free radical as demonstrated by direct electron spin resonance techniques. The formation of this species is inhibited by carbon monoxide and metyrapone, suggesting the involvement of cytochrome P-450. Either NADPH or NADH can serve as a source of reducing equivalents for the production of this free radical. Related triarylmethane dyes are also shown to be reduced by the monooxygenase system to form free radicals.