SCAVENGING OF THE ONE-ELECTRON REDUCTION PRODUCT FROM NISOLDIPINE WITH RELEVANT THIOLS - ELECTROCHEMICAL AND EPR SPECTROSCOPIC EVIDENCES

Purpose. To determine the formation of the one-electron reduction prod uct from nisoldipine and its reactivity with relevant thiols in mixed medium. Methods. Cyclic voltammetry (CV) and electron paramagnetic res onance (EPR) techniques were used to determine the one-electron reduct ion product corresponding to the nitro radical anion. CV was employed to assess both the rate constants corresponding to the decay of the ra dicals and its interaction with relevant thiols. Results. The nisoldip ine radical anion follows second order kinetics, with an association r ate constant of 283 +/- 1.61mol(-1) sec(-1). Nitro radical anion from nisoldipine significantly reacted with thiol compounds. This reactivit y was significantly higher than the natural decay of the radical in mi xed medium. EPR spectra recorded in situ using DMF/0.1 N NaOH (pH 13) confirmed the formation of the nitro radical anion, giving a well-reso lved spectra in 35 lines using 0.1 G modulation. Conclusions. Electroc hemical and EPR data indicated that all the tested thiols scavenged th e nitro radical anion from nisoldipine. The following tentative order of reactivity towards the thiols can be proposed: cysteamine similar t o glutathione > N-acetylcysteine > captopril > penicillamine.