Abstract

Megazol (2-amino-5-(1-methyl-5-nitro-2-imidazolyl)-1,3,4-thiadiazol, CAS 19622-55-0), a highly active compound used against several strains of Trypanosoma cruzi, the causative agent of Chagas disease, is electrochemically studied to propose a new electroanalytical alternative for its quantitative determination. Megazol is shown to be polarographically reducible in protic and mixed media. The polarogram of megazol shows two signals, the main signal is due to the reduction of the nitroimidazole moiety, and the second one is due to the reduction of the thiadiazole moiety in the molecule. We have synthesized several related molecules to megazol in order to study the influence of structural changes in the reducibility of the nitro group. Also we have compared the polarographic behavior of megazol with the currently used antichagasic drug, benznidazole. Based on the linear relation between the peak current and the megazol concentrations a differential pulse polarographic method was developed. The linearity was maintained between 6 × 10-6 and 1 × 10-4 M with a quantitation and detection limits of 6.7 × 10-6 and 3.2 × 10-6 M, respectively. Precision and accuracy of the developed method was checked by recovery study. For comparative purposes spectrophotometric and HPLCuv methodologies were developed. From the pH dependence of the absorbance band at 276 nm an apparent pKa of 8.5 was determined for megazol.