Identification of the urinary metabolites of 4-bromoaniline and 4-bromo-[carbonyl-13C]-acetanilide in rat.

1. The urinary excretion of 4-bromoaniline and its [carbonyl-(13)C]-labelled N-acetanilide, together with their corresponding metabolites, have been investigated in the rat following i.p. administration at 50 mg kg(-1). 2. Metabolite profiling was performed by reversed-phase HPLC with UV detection, whilst identification was performed using a combination of enzymic hydrolysis and directly coupled HPLC-NMR-MS analysis. The urinary metabolite profile was quantitatively and qualitatively similar for both compounds with little of either excreted unchanged. 3. The major metabolite present in urine was 2-amino-5-bromophenylsulphate, but, in addition, a number of metabolites with modification of the N-acetyl moiety were identified (from both the [(13)C]-acetanilide or produced following acetylation of the free bromoaniline). 4. For 4-bromoacetanilide, N-deacetylation was a major route of metabolism, but despite the detection of the acetanilide following the administration of the free aniline, there was no evidence of reacetylation (futile deacetylation). 5. Metabolites resulting from the oxidation of the acetyl group included a novel glucuronide of an N-glycolanilide, an unusual N-oxanilic acid and a novel N-acetyl cysteine conjugate.