Mechanism and kinetics of olanzapine and quetiapine oxidations at glassy carbon electrode

Abstract

The electrochemical oxidation mechanisms of highly used anti-psychotic drugs olanzapine and quetiapine were systematically studied using cyclic voltammetry in 0.1 M phosphate buffer solutions, at different pH values to better understand their reactivity, effect and eventually its side effects. Olanzapine presents four redox processes: I, which forms a reversible redox process with a cathodic process; II, a proton coupled electron transfer, involving one proton and one electron that occurs at the outer nitrogen of the benzodiazepine ring and have two follow up chemical steps which compete against each other, a dimerization in an EC2 and a nucleophilic addition in an EC mechanism. The EC mechanism was successfully simulated, and the kinetic parameters were obtained. The processes III and IV are present in both molecules and were ascribed to a sequential oxidation at the outer nitrogen of the piperazine ring, which initially forms an ammonium radical via a proton coupled electron transfer, process III, to later form an imine in process IV.