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 1,4-DHP reacts with O·− 2. The following order of rates was obtained: felodipine ≥ 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.