Electrochemistry–Mass Spectrometry for Generation and Identification of Metabolites of Selected Drugs from Different Therapeutic Groups in Comparison with In Vitro and In Vivo Approaches

The metabolism of antibiotics, antidepressants, and cardiovascular drugs has been investigated widely over the last few decades. The aim of this study was to develop an efficient analytical protocol based on the combination of electrochemistry (EC) and mass spectrometry for the identification of electrochemical products (potential pharmacologically active metabolites) of selected drugs (enalapril, metronidazole, midazolam, propranolol, venlafaxine). The electrochemical mimicry of the oxidative phase I and II metabolism was achieved in a thin-layer cell equipped with different working electrodes (magic diamond (MD), glassy carbon (GC), gold (Au), platinum (Pt)). The structures of the electrochemically generated metabolites were elucidated based on accurate mass ion data and tandem mass spectrometry (MS/MS) experiments. The in silico prediction of the main sites of selected drugs’ metabolism was performed using Biotransformer 3.0, GLORYx, and Xenosite software. Moreover, incubation with liver microsomes (LMs) was performed to examine the proposed metabolic pathways of target compounds. The data from in vitro experiments agreed with the data from electrochemical oxidation, which predicted some potential metabolites found in the real samples from patients. For enzymatic incubation, N-dealkylation, O-demethylation, and hydroxylation were the metabolic pathways involved mainly in their metabolism. Their in vitro phase II metabolites were identified as glucuronic acid conjugates. Finally, different in vivo phase I and II metabolites were identified for the studied drugs, including metabolic pathways for in vivo phase I N-demethylation, N-dealkylation, O-demethylation, and hydroxylation, while the metabolic pathways for in vivo phase II metabolites were identified as glucuronic acid conjugates.