Preparation and application of a carbon paste electrode modified with multi-walled carbon nanotubes and boron-embedded molecularly imprinted composite membranes.

An innovative electrochemical sensor was fabricated for the sensitive and selective determination of tinidazole (TNZ), based on a carbon paste electrode (CPE) modified with multi-walled carbon nanotubes (MWCNTs) and boron-embedded molecularly imprinted composite membranes (B-MICMs). Density functional theory (DFT) calculations were carried out to investigate the utility of template-monomer interactions to screen appropriate monomers for the rational design of B-MICMs. The distinct synergic effect of MWCNTs and B-MICMs was evidenced by the positive shift of the reduction peak potential of TNZ at B-MICMs/MWCNTs modified CPE (B-MICMs/MWCNTs/CPE) by about 200 mV, and the 12-fold amplification of the peak current, compared with a bare carbon paste electrode (CPE). Moreover, the coordinate interactions between trisubstituted boron atoms embedded in B-MICMs matrix and nitrogen atoms of TNZ endow the sensor with advanced affinity and specific directionality. Thereafter, a highly sensitive electrochemical analytical method for TNZ was established by different pulse voltammetry (DPV) at B-MICMs/MWCNTs/CPE with a lower detection limit (1.25 × 10-12 mol L-1) (S/N = 3). The practical application of the sensor was demonstrated by determining TNZ in pharmaceutical and biological samples with good precision (RSD 1.36% to 3.85%) and acceptable recoveries (82.40%-104.0%).

[Study of serum concentrations and urinary excretion of secnidazole after oral administration in man. Comparison with tinidazole]. / Etude des taux sériques et de l'élimination urinaire du secnidazole après administration orale chez l'homme. Comparaison avec le tinidazole.

Secnidazole, a derivative of 5-nitro imidazole exhibits trichomonacid, amoebicid and antimicrobial properties; it has been studied in view of its biological fate in healthy volunteers (man and woman) comparatively with tinidazole. Both products were administered orally to the same volunteers at the single dose level of 2 g. The seric concentrations and the pharmacokinetic profile were determined up to the 72nd hour after drug administration. The whole urinary excretion (unchanged product + metabolites) during the same period was determined in percent of the administered dose level. Secnidazole is particularly different from tinidazole owing to its slower blood clearance. The apparent average half-life in the ten volunteers (5 men and 5 women) is about 17 hours for secnidazole and 13 hours for tinidazole. However, for both drugs, a difference between men and women was demonstrated: in female volunteers, the decrease in blood concentrations occurs a little quicker than in male volunteers. Regarding urinary excretion, it is also a little greater in female volunteers than in male volunteers.

Metabolism of 5-isopropyl-1-methyl-2-nitro-1H-imidazole. Identification of some urinary metabolites in the dog.

The metabolism of 5-isopropyl-1-methyl-2-nitro-1H-[2-14C] imidazole in dogs has been investigated after oral administration of 50 mg/kg. Three main metabolites, still containing the nitro group and accounting for about 50% of the total radiocarbon, together with a small amount of the unchanged drug, were isolated from the urine within 48 hr. The structures were determined by mass, infrared, and nuclear magnetic resonance spectroscopy. The biotransformations giving rise to the metabolites isolated involve the isopropyl chain of the molecule, either at the tertiary carbon atom or at one of the two methyl groups, or both. Thus, the metabolic behavior of this 2-nitroimidazole derivative appears to be similar to that previously demonstrated for the class of the isomeric 5-nitroimidazoles.