The N-oxidation of benzamidines in vitro.

The enzymic N-oxidation of a series of N-unsubstituted basic benzamidines (I) to a new type of metabolite, the amidoximes (II), is reported. Rabbit liver homogenates (9000 g supernatant) were used as enzyme source, and metabolites were identified by t.l.c. and mass spectral analysis using synthetic reference compounds. The microsomal NADPH- and oxygen-dependent hydroxylation of benzamidines was not detected after incubation of benzamidine in the presence of SKF 525-A, a known inhibitor of cytochrome P-450. Neither benzamidine or p-methoxybenzamidine is a good substrate for purified microsomal FAD-containing mono-oxygenase.