Electrochemistry of thiobarbiturates: correlation of structure with reduction potential and drug activity

Metronidazole radical anion formation studied by means of electrochemical impedance spectroscopy

Radiosensitizers belong to the most important class of the cancerostatic drugs. The electrochemical transfer of the first electron to the cytotoxic radiosensitizer Metronidazole (MET) and MET radical anion formation in aprotic medium was studied by means of electrochemical impedance spectroscopy. The heterogeneous electron transfer rate constant for the first reduction of MET (radical anion production) k0 for the redox couple was determined. Similarly, the diffusion coefficient of MET in dimethylformamide was also calculated by impedance measurements using expression for Warburg coefficient and Warburg plot. Moreover, the equivalent circuit for the redox couple MET/MET•– was proposed and its parameters were evaluated using a non-linear least square fitting. Our results, from the electrochemical point of view, also confirm the suitability of MET for the effective treatment of selected types of the cancer.

Impedance study of hypoxic cells radiosensitizer etanidazole radical anion in water

Electrochemical transfer of the first electron to cytotoxic radiosensitizer etanidazole (ETN) and ETN radical anion formation in the alkaline buffered aqueous solution were studied by means of electrochemical impedance spectroscopy (EIS). The heterogeneous electron transfer rate constant for the first reduction of ETN (radical anion production), k0, was calculated. The value of k0 from EIS measurements and the previously obtained value of so-called E71 potential indicate that ETN, compared with other possible chemical radiosensitizers, requires lower energy to accept the first electron during the metabolic pathway. However, the necessity of the alkaline pH may decrease the ability of ETN to act as hypoxic radiosensitizer in the human body.