Lidocaine oxidation by electrogenerated reactive oxygen species in the light of oxidative drug metabolism.

The study of oxidative drug metabolism by Cytochrome P450s (P450) is important in the earlier stages of drug development. For this purpose, automated analytical techniques are needed for fast and accurate estimation of oxidative drug metabolism. Previous studies have shown that electrochemistry in combination with mass spectrometry is a versatile analytical technique to generate drug metabolites that result from direct electron transfer. Here we show that electrochemical generation of reactive oxygen species (ROS), a process reminiscent of the catalytic cycle of P450, extends the applicability of electrochemistry in drug metabolism research. Oxidation products of lidocaine from one and two-compartment electrochemical cells, operated under various conditions were analyzed by LC-MS and metabolite structures were elucidated by collision-induced (LC-MS/MS), and thermally induced (APCI) fragmentation. Direct oxidation of lidocaine at the anode resulted in N-dealkylation, whereas reaction with H(2)O(2), generated at the cathode, produced the N-oxide, both known in vivo lidocaine metabolites. Catalytic activation of hydrogen peroxide, using the Fenton reaction, resulted in benzylic and aromatic hydroxylations thus covering all of the known in vivo phase-I metabolites of lidocaine. This study extends the applicability of electrochemistry combined with mass spectrometry as a valuable technique in assessing oxidative drug metabolism related to P450.