IDENTIFICATION OF NEW METABOLITES OF IFOSFAMIDE IN RAT URINE USING ION CLUSTER TECHNIQUE

Metabolism of the anticancer drug ifosfamide was investigated in Sprague-Dawley rats. Along with four known metabolites, namely N-2-dechloroethylifosfamide, N-3-dechloroethylifosfamide, alcoifosfamide and isophosphoramide mustard, four new urinary metabolites were identified utilizing combined techniques of chemical modification/derivatization, capillary gas chromatography/chemical ionization mass spectrometry (ammonia), deuterium-labeliag/ion cluster analysis and chemical synthesis. Secondary metabolites-of N-2-dechloroethyl and N-3-dechloroethylifosfamide formed by 4-hydroxylation, i.e. 4-hydroxy-N2-dechloroethylifosfamide and 4-hydroxy-N-3-dechloroethylifosfamide, respectively, and their subsequent decomposition product, N-dechloroethylisophosphoramide mustard, were identified. Secondary dealkylation pathways of N-2-dechloroethylifosfamide and/or N-3-dechloroethylifosfamide were also demonstrated through characterization of N-2,N-3-didechloroethyl ifosfamide. The key active metabolite of ifosfamide, 4-hydroxyifosfamide, was characterized as a cyanohydrin adduct for the first time.