Relative reactivity of dihydropyridine derivatives to electrogenerated superoxide ion in DMSO solutions: A voltammetric approach

Purpose. To evaluate the reaction of a large series of pharmacologically significant 1,4-dihydropyridine (1,4-DHP) compounds with superoxide (O-2(.-)) in dimethylsulfoxide using differential pulse voltammetry and controlled potential electrolysis. Methods. Differential pulse voltammetry was used to track the consumption of O-2(.-), and controlled potential electrolysis was used to electrogenerate O-2(.-). Results. With the addition of 1,4-DHP, the oxidation peak current of O-2(.-) decreased concentration dependently, suggesting that 1,4-DHP reacts with O-2(.-), that is, 1,4-DHP scavenges O-2(.-) in dimethylsulfoxide. Conclusions. A very easy and direct voltammetric procedure to study the relative reactivity of different 1,4-DHP with O-2(.-) is proposed. Using the proposed method we have found that all commercial 1,4DHP reacts with O-2(.-). The following order of rates was obtained: felodipine greater than or equal to vitamin E > isradipine > nimodipine > furnidipine > nitrendipine > nisoldipine > nifedipine. Furthermore, it was demonstrated that the hydrogen at the N-position of 1,4-DHP compounds could be released as a proton in the presence of O-2(.-), thus the electrogenerated O-2.- worked as a proton acceptor to 1,4-DHP