NITRO RADICAL-ANION FORMATION FROM NIFURTIMOX .2. ELECTROCHEMICAL EVIDENCE

The cyclic voltammetric (CV) behaviour of nifurtimox was studied. The addition of aprotic solvent (DMF) to nifurtimox in an aqueous citrate buffer system was examined. Qualitatively this results in separation o f the initial irreversible four-electron reduction into two stages, th e R-NO2/R-NO2- and R-NO2-,4H(+)/R-NHOH,H2O couples respectively. Parti cular attention was directed to the one-electron R-NO2/R-NO2- couple a s measured by the CV mode in mixed media. Analysis of the CV response as a function of scan rate and non-aqueous solvent content yields info rmation on the stability of the radical anion. The chemical forward re action of the radical anion follows a second-order kinetic with a stab ility constant of 954 L mol(-1) s(-1) and a half-life of 1.05 s for 1 mM nifurtimox in aqueous citrate buffer, pH 10.5, + DMF, 40:60.