Voltammetric Behaviour of Metronidazole at Mercury Electrodes

Abstract

Metronidazol é o fármaco mais importante do grupo de 5-nitroimidazoles, possuindo toxicidade contra microrganismos anaeróbicos, sendo a molécula de DNA o principal alvo de sua ação biológica. O mecanismo de ação do metronidazol depende do processo de redução do grupo nitro e, em meio ácido, a redução é pH-dependente envolvendo quatro elétrons na completa redução ao derivado hidroxilamínico. Em meio aprótico a redução do metronidazole acontece em duas etapas: a primeira envolvendo um elétron para formar o radical nitro e a segunda etapa envolve mais três elétrons até a formação da hidroxilamina. Neste artigo o mecanismo de redução do metronidazol foi estudado utilizando as técnicas voltamétricas: polarografia d.c. e pulso diferencial, voltametria cíclica usando o eletrodo gota de mercúrio como eletrodo de trabalho. Metronidazole is the most important drug of the group of 5-nitroimidazoles and possesses toxicity to anaerobic microorganisms DNA being the main target for their biological action. The mechanism of biological action of metronidazole is dependent upon the nitro group reduction process. The reduction of metronidazole is pH dependent in acid medium and four electrons are involved in the complete reduction to the hydroxylamine derivative. In aprotic medium the reduction of the metronidazole occurs in two steps, the first involving one electron to form the nitro radical and the second step involving three more electrons until the formation of the hydroxylamine derivative. In this paper the mechanism of reduction of metronidazole was studied by using the voltammetric techniques: d.c. polarography, differential pulse polarography and cyclic voltammetry using the mercury drop as the working electrode.

Voltammetric behavior of benznidazole at a DNA-electrochemical biosensor

“…Theoretically, the nitro group can receive up to six electrons in the complete reduction to the amine derivative [1,3,19]. Voltammetric nitroimidazole reduction indicated nitroso (R-NO) and hydroxylamine (R-NHOH) derivative formation, involving a total of four electrons, as shown in Scheme 1 [19]. nitroimidazole [20,21], benznidazole reduction is also pH-dependent in acidic medium, the reduction peak potential being shifted to negative values with increasing pH.…”

“…Theoretically, the nitro group can receive up to six electrons in the complete reduction to the amine derivative [1,3,19]. Voltammetric nitroimidazole reduction indicated nitroso (R-NO) and hydroxylamine (R-NHOH) derivative formation, involving a total of four electrons, as shown in Scheme 1 [19].…”

“…Because the voltammetric behaviour of nitroimidazoles and their interactions with DNA bases had previously been studied using mercury electrodes [13,19,25,30], it was not possible due to the mercury electrode to investigate the anodic region. The use of the DNA-biosensor allowed the anodic voltammetric study of nitroimidazoles and led to an explanation for the differences in reactivity between 5-nitroimidazoles and 2-nitroimidazoles.…”

“…The voltammetric reduction of 5-nitroimidazoles using mercury [19] and solid [20,21] electrodes has been investigated. The mechanism of action of nitroimidazole as antimicrobial agent [11], and for the analysis of pharmaceutical [22,23] and clinical samples [22,24] was also studied voltammetrically.…”

Flow injection determination of metronidazole through spectrophotometric measurement of the nitrite ion produced upon alkaline hydrolysis

“…2 Although this later one is kind of simple, being daily practiced in many routine analysis laboratories, it is time consuming and very tedious as it is based on the use of acetic anhydride. Various research studies have been devoted to the development of new high performance alternative methods for determination of the drug in dosage forms using different techniques such as high performance liquid chromatography, 3 supercritical fluid chromatography, 4 differential pulse polarography 5 and voltammetry with glassy carbon electrode 6 or chemically modified electrodes. 7 Flow analysis approaches have also being successfully applied on developing fast analytical methods for determination of some antihelmintic and antiprotozoal with spectrometric [8][9][10] and biamperometric detection in dosage forms.…”