Use of stable isotopes in studies on the metabolism of amphetamine (1)

Microsomal coincubation of 1,1,1- 2H 3-amphetamine and unlabelled N-hydroxyamphetamine yielded 2H-incorporation into recovered N-hydroxyamphetamine. The mole fraction of 2H in recovered phenylacetone was always close to but less than one, indicating that N-hydroxyamphetamine is not a necessary intermediate in the formation of phenylacetone. However, coincubation of 2H-labelled hydroxylamine with unlabelled 2-nitro-1-phenylpropane indicated an incorporation of 2H into both recovered nitro compound and phenylacetone. Some phenylacetone is thus formed from the nitro metabolite. Similar experiments showed phenylacetone oxime not to be a necessary intermediate in the conversion of hydroxylamine to the nitro compound. Incubation of phenyl-labelled ( 2H) phenylacetone gave 5 deuterium-labelled metabolites, including small quantities of labelled benzoic acid, indicating that it is a true though minor metabolite.