Acebutolol and alprenolol metabolism predictions: comparative study of electrochemical and cytochrome P450-catalyzed reactions using liquid chromatography coupled to high-resolution mass spectrometry

Abstract

A comparative study of the electrochemical conversion and the biotransformation performed by the cytochrome P450 (CYP450) obtained by rat liver microsomes has been achieved to elucidate the oxidation mechanism of both acebutolol and alprenolol. For this purpose, a wide range of reactions such as N-dealkylation, O-dealkoxylation, aromatic hydroxylation, benzyl hydroxylation, alkyl hydroxylation, and aromatic hydroxylation have been examined in this study, and their mechanisms have been compared. Most of the results of the electrochemical oxidation have been found to be in accordance with those obtained by incubating acebutolol and alprenolol in the presence of CYP450, i.e., N-dealkylation, benzyl hydroxylation, and O-dealkoxylation reactions catalyzed by liver microsomes were found to be predicted by the electrochemical oxidation. The difficulty for the electrochemical process to mimic both aromatic and alkyl hydroxylation reactions has also been discussed, and the hypothesis for the absence of aromatic hydroxylated and alkyl hydroxylated products, respectively, for alprenolol and acebutolol, under the anodic oxidation has been supported by theoretical calculation. The present study highlights the potential and limitation of coupling of electrochemistry-liquid chromatography-high-resolution mass spectrometry for the study of phase I and phase II reactions of acebutolol and alprenolol.

Electrochemistry-mass spectrometry to study reactive drug metabolites and CYP450 simulations

“…As presented above in the haloperidol example, EC is able to mimic the CYP450 reaction [16], and other reaction intermediates have been assumed identical between the enzyme-catalyzed reaction and the electrochemical-simulation tool [7]. For example, the electrochemical benzyl hydroxylation of the alprenolol molecule has been shown to occur through the formation of a carbocation on the benzylic position, while CYP450 reactions can initiate the hydroxylation of both radical and carbocationic intermediates [9]. Benzylic reactive intermediates may lead to heme alkylation and CYP450 inhibition [52].…”

“…Benzylic reactive intermediates may lead to heme alkylation and CYP450 inhibition [52]. Comparison of EC-MS and CYP450 can only be assumed on the basis of the formation of identical products, and the elucidation of pathways can sometimes be supported by theoretical modeling [9] or chemical trapping [16,20]. Future research into carbocation and radical reaction intermediates should certainly consider the in situ ESI EC-MS instrument set-up [53].…”

“…2) [20,22,30] and acebutolol [9,31,32] were chosen as models of aromatic ether O-dealkylation. Lohmann et al reported the comparison between electrochemical oxidation and rat-liver microsome incubations for three active pharmaceutical ingredients [15].…”

“…Electrochemical cells may constitute a valuable tool for the generation of a series of putative metabolites. First, the match between the metabolites generated electrochemically and enzymatically can provide a clue to the nature of their metabolic pathway initiation and open up further perspectives [9]. Second, the electrochemical reaction can be scaled up to produce metabolites in sufficient amounts for subsequent DMPK (Drug Metabolism and Pharmacokinetics) studies of metabolite or structural characterization.…”

Unexpected benzimidazole ring formation from a quinoneimide species in the presence of ammonium acetate as supporting electrolyte used in the coupling of electrochemistry with mass spectrometry

“…During the last decade, several studies have reported the use of an electrochemical cell not as a detector, but as a tool for generating oxidative degradation products . Electrochemistry has been found to be able to simulate various reactions mediated by cytochrome P450 (CYP450) especially those initiated by a single‐electron transfer (SET) . One of the advantages of EC/MS compared to biological systems (liver slices, microsomes, etc.)…”