Agradecimentos: The authors would like to thank Spinell Bacil and Gaspy Serrano (in memoriam) for all the support and friendship throughout the years. The authors would like to thank the CNPq projects n° 140833/2016-1 and 310114/2016-0, CAPES project 88881.187396/2018-01 and Fapesp for the grants and funding. Finally, the authors would like thank Professor Lucas C. V. Rodrigues which kindly allowed us to use his laboratory, and to Professor Ana Maria da Costa Ferreira for the access to EPR instrument, supported by the CEPID-Redoxoma Network (FAPESP grant 2013/07937-8) Ver menos

Abstract: Mental disorders like schizophrenia affect about 0.7% of the world population. Nowadays, the treatment consists of atypical antipsychotic drugs, mainly olanzapine and quetiapine. In this paper, we observed the chemical interaction between both olanzapine and quetiapine, antipsychotic drugs, with dopamine in phosphate buffer solutions at physiological pH using cyclic and differential voltammetry techniques, UV–Vis and EPR spectra. A solution containing both antipsychotic drugs and dopamine resulted in a shift of dopamine's redox processes, hindering its electrochemical oxidation. The chemical interaction was voltametrically investigated and a mechanism is proposed. In addition, it was observed that the reactions of both drugs with DA are first-order, presenting kinetic rate constants of 1.5 10-2 s-1 and 9.0 10-3 s-1 for olanzapine and quetiapine, respectively, at pH = 7.4. To further evaluate the chemical reaction, a minimalist model between PIPES molecule and catechol was proposed and tested. The model presented a similar signal decrease and kinetic rate constant to those observed for both olanzapine and quetiapine reaction with dopamine, reinforcing the data obtained which strongly suggests that the chemical reaction occurs between piperazine and catechol moieties Ver menos