Use of on-line hydrogen/deuterium exchange to facilitate metabolite identification

Biotransformation studies performed on an investigational compound (I, repr esented by R1-CH(NH2)-CO-N(R2)-CH2-S-R3) led to the identification of five metabolites (M1-M5). Based on LC/MS (liquid chromatography/mass spectrometr y) analysis which included the use of H2O and D2O in the mobile phases, the y were identified as the sulfoxide (Ml), sulfone (M2), carbamoyl glucuronid e (M3), N-glucuronide (M4), and N-glucoside (M5) metabolites, respectively. The structure of M3, a less commonly seen carbamoyl glucuronide metabolite , was established using on-line H/D (hydrogen/deuterium) exchange experimen ts conducted by LC/MS. H/D exchange experiments were also used to distingui sh the S-oxidation structures of M1 and M2 from hydroxylation. Herein, the application of deuterium oxide as the LC/MS mobile phase for structural elu cidation of drug metabolites in biological matrices is demonstrated. Copyri ght (C) 2001 John Wiley & Sons, Ltd.