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%).

Establishment of a de novo Reference Transcriptome of Histomonas meleagridis Reveals Basic Insights About Biological Functions and Potential Pathogenic Mechanisms of the Parasite.

The protozoan flagellate Histomonas meleagridis is the causative agent of histomonosis in poultry. In turkeys, high mortality might be noticed whereas in chickens the disease is less severe despite production losses. Discovered over a century ago, molecular data on this parasite are scarce and genetic studies are in its infancy. To expand genomic information, a de novo transcriptome sequencing of H. meleagridis was performed from a virulent and an attenuated strain, cultivated in vitro as monoxenic mono-eukaryotic culture. Normalized cDNA libraries were prepared and sequenced on Roche 454 GS FLX resulting in 1.17 million reads with an average read length of 458bp. Sequencing reads were assembled into two sets of >4500 contigs, which were further integrated to establish a reference transcriptome for H. meleagridis consisting of 3356 contigs. Following gene ontology analysis, data mining provided novel biological insights into proteostasis, cytoskeleton, metabolism, environmental adaptation and potential pathogenic mechanisms of H. meleagridis. Finally, the transcriptome data was used to perform an in silico drug screen to identify potential anti-histomonal drugs. Altogether, data recruited from virulent and attenuated parasites facilitate a better understanding of the parasites' molecular biology aiding the development of novel diagnostics and future research.

A novel method for tinidazole detection using Mn-modified CdSe/CdS quantum dots as a luminescent probe.

A new method for the determination of tinidazole based on the fluorescence quenching of citrate-capped Mn-modified CdSe/CdS quantum dots was developed. In aqueous solution, the fluorescence of the quantum dots at 610 nm was quenched gradually with the increase of the concentration of tinidazole. Based on this, a simple, fast, low-cost and specific quantitative method for tinidazole detection was set up. Under optimal conditions, a good linearity was built between the fluorescence quenching of Mn-modified CdSe/CdS quantum dots and the concentration of tinidazole in the range of 4-400 microM with a correlation coefficient of 0.9998. The limit of detection (3sigma/K) was 0.4 microM. The proposed method was applied to the detections of tinidazole in tablets and injections with satisfactory results.

An interlaboratory investigation on the use of high-performance thin layer chromatography to perform assays of lamivudine-zidovudine, metronidazole, nevirapine, and quinine composite samples.

Two laboratories extensively investigated the use of HPTLC to perform assays on lamivudine-zidovudine, metronidazole, nevirapine, and quinine composite samples. To minimize the effects of differences in analysts' technique, the laboratories conducted the study with automatic sample application devices in conjunction with variable-wavelength scanning densitometers to evaluate the plates. The HPTLC procedures used relatively innocuous, inexpensive, and readily available chromatography solvents used in the Kenyon or the Global Pharma Health Fund Minilabs TLC methods. The use of automatic sample applications in conjunction with variable- wavelength scanning densitometry demonstrated an average repeatability or within-laboratory RSD of 1.90%, with 73% less than 2% and 97% at 2.60% or less, and an average reproducibility or among-laboratory RSD of 2.74%.

Study on the compatibility of cefotaxime with tinidazole in glucose injection.

An efficient HPLC method for the compatibility study of cefotaxime with tinidazole in glucose injection is described, which has been developed for the simultaneous determination of cefotaxime and tinidazole in glucose injection. The appearance and pH value of the mixed solution were investigated and the concentrations of cefotaxime and tinidazole were determined by RP-HPLC with an Agilent ZORBAX Eclipse XDB-C8 column, gradient elution and dual wavelength detection on diode-array-detector (DAD) at room temperature (20 degrees C) within 24 h. It was found that the resulting appearance and pH value of the mixed solution showed slight changes, on the other hand, the quantity of cefotaxime decreased significantly. The results show that the mixed solution of cefotaxime with tinidazole in glucose injection must be used within 8 h in clinical due to the possible degradation of cefotaxime in tinidazole glucose injection. This study provides a convenient method for rational use of compatible drugs in clinical practice.

A stability-indicating HPLC assay for metronidazole benzoate.

A simple and rapid stability-indicating HPLC assay procedure has been developed and validated for metronidazole benzoate. The HPLC conditions were as follows, column: Waters Symmetry C8, 5 microm packing, 4.6 mm x 250 mm; detection: UV at 271 nm; injection volume: 20 microl; mobile phase: acetonitrile-0.1% glacial acetic acid in monobasic potassium phosphate (0.01 M) (40:60, v/v); isocratic elution under ambient temperature at 2.0 ml min(-1). The procedure separated metronidazole benzoate and its potential degradation products, metronidazole and benzoic acid, in an overall analysis time of about 6 min with metronidazole benzoate eluting at about 5 min. The injection repeatability was 0.03%, and the intraday and interday repeatability were 0.4 and 0.7%, respectively. The procedure provided a linear response over the concentration range 0.2-800 microg ml(-1) (r=1.0000) with the limits of detection and quantitation 0.03 and 0.2 microg ml(-1), respectively. The solubilities of metronidazole benzoate in water, 0.01 M hydrochloric acid and 0.05 M phosphate buffer, pH 6.8, determined each in triplicate using the procedure, were 0.2 mg ml(-1) (R.S.D. 7%), 0.4 mg ml(-1) (R.S.D. 2%) and 0.2 mg ml(-1) (R.S.D. 8%), respectively. The results show no detectable hydrolysis of metronidazole benzoate in 0.01 M hydrochloric acid at 37 degrees C or in the mobile phase at ambient temperature in 10 h.

Two stability-indicating UV spectrophotometric methods for the analysis of hydrolyzed tinidazole.

Two UV spectrophotometric methods have been validated for the analysis of hydrolyzed tinidazole solutions. The pH of the samples must be 5.00-7.00 for both methods. The multiwavelength method may be used for samples degraded at pH 6-12 if the amount of conserved 5-nitroimidazole species is at least 93 mol.% of the original; the amounts of tinidazole and its two known impurities may be determined simultaneously. The accuracy was within 100+/-8% and the repeatability of measurement was

Use of solid phase extraction for the isolation and clean-up of a derivatised furazolidone metabolite from animal tissues.

A method is presented for the determination of protein-bound residues of furazolidone in animal tissue. The use of furazolidone in food-producing animals has been banned in the EU. Illegal use of furazolidone can be monitored most effectively by testing for bound residues containing the 3-amino-2-oxazolidone (AOZ) moiety which, unlike the parent drug, is stable and can be detected for prolonged periods after cessation of treatment. This paper reports the development of an extraction and clean-up procedure for AOZ from liver using solid phase extraction. The method replaces solvent extraction and provides extensive sample clean-up with removal of approximately 99% of the derivatising agent, 2-nitrobenzaldehyde, which may interfere with the determination. It also offers the advantage of being suitable for automation, thereby increasing throughput of samples. The extraction procedure may be used for HPLC and ELISA screening techniques. The method has been validated in fortified and incurred pig liver samples, yielding mean recovery of AOZ in excess of 60%.

Spectrophotometric determination of metronidazole and tinidazole in pharmaceutical preparations.

Sensitive and simple spectrophotometric methods for the determination of metronidazole (MNZ) and tinidazole (TNZ) in either pure form or in its pharmaceutical formulations are described. The first method is based on the interaction of 3-methylbenzothiazolin-2-one hydrazone (MBTH) with MNZ/TNZ (reduced drug) in presence of copper sulphate and pyridine in acidic medium. The resulting yellowish orange products have lambda(max) of 500 and 490 nm, respectively, for MNZ and TNZ and are stable for about 4 h. The second method describes the reaction between reduced diazotised drugs with N-(1-naphthyl)ethylenediamine dihydrochloride (NEDA) in neutral medium to yield pink products which have lambda(max) of 520 and 505 nm, respectively, for MNZ and TNZ, respectively. The products are stable for more than 24 h. Common excipients used as additives in pharmaceutical preparations do not interfere in the proposed method. Both the methods are highly reproducible and have been applied to a wide variety of pharmaceutical preparations and the results compare favourably with those of official methods.

Electrochemical study on the determination of tinidazole in tablets.

The electrochemical reduction of tinidazole has been carried out in aqueous solution in the pH range 1.8-11.3 by differential-pulse (DP) polarography. Tinidazole exhibits one or two reduction peaks depending on pH. In strongly acidic solution (pH < 4.5), one reduction peak was obtained and it was suitable for analytical purposes. A method for the determination of tinidazole by DP polarography in Britton-Robinson buffer of pH 3.0, which allows quantification over the range 0.03-7.30 microg/ml, was proposed. The method was successfully applied to the determination of tinidazole in tablets with mean recovery and relative standard deviation of 98.7 and 3%, respectively. Excipients did not interfere in the determination.

Electrochemical reduction of metronidazole at activated glassy carbon electrode and its determination in pharmaceutical dosage forms.

A voltammetric method has been developed for the determination of metronidazole in dosage forms. The method is based on the electrochemical reduction of the drug at a glassy carbon electrode activated by applying a new pretreatment. The influence of pH, concentration, scan rate and presence of organic solvent and surfactant has been studied. The current is proportional to the concentration and permits the drug to be determined in the concentration range 2 x 10(-6)-6 x 10(-4) M in Britton-Robinson buffer (pH 10). Furthermore, results obtained by the proposed method have been compared with USP XXIII procedure which involves a HPLC method.

Application of the bivariate spectrophotometric method for the determination of metronidazole, furazolidone and di-iodohydroxyquinoline in pharmaceutical formulations.

The bivariate calibration algorithm was applied to the spectrophotometric determination of metronidazole, furazolidone and di-iodohydroxyquinoline in pharmaceutical dosage forms. The results obtained were compared with the results of derivative spectrophotometry. The statistical evaluation of method bias was carried out, and it was shown that the proposed procedure may be competitive with commonly used first-derivative spectrophotometry. The advantage of the bivariate calibration is its simplicity, and the fact that there is no need to use the derivatization procedures.

A liquid chromatography assay for the study of serum and gastric juice metronidazole concentrations in the treatment of Helicobacter pylori.

Metronidazole is an important component of combination antimicrobial therapies used in the eradication of Helicobacter pylori, a recognized cause of gastritis and duodenal ulcer. Studies are needed to understand which pharmacokinetic factors determine the success of metronidazole therapy and what role drug monitoring plays. Such studies require a rapid, accurate assay for small volumes of sample, including gastric juice, over a 200-fold range of concentrations. Using an isocratic high-performance liquid chromatography (HPLC) method, with an 8-min run time and protein precipitation of samples, metronidazole could be measured reliably to as low as 0.5 mg/L in 100 microliters samples of serum, gastric juice, or saliva. Standard curves for serum and gastric juice were linear between 0.5 and 50 mg/L. Within-day coefficients of variation (CVs) (n = 5 at six concentrations) ranged from 1.1 to 4.8% over this range and the between-day CV (n = 7 days) was 5.8%. Neither omeprazole nor common gastroenteric and cardiac medications interfered with this assay. A pilot study, done in four healthy volunteers given intravenous metronidazole 500 mg before and after 7 days of omeprazole therapy, found metronidazole to be present in higher concentrations in gastric juice and saliva than in serum 2 h after intravenous administration. The range and accuracy of the assay proved to be suitable for carrying out pharmacokinetic studies at clinically used doses of the drug.

High performance thin layer chromatographic analysis of hydrolyzed tinidazole solutions. I. Development and validation method.

A stability-indicating high performance thin layer chromatography method for analyzing hydrolyzed tinidazole solutions using silica gel plates was developed and validated. The mobile phase used was methanol-diethyl ether-chloroform (1:9:3, v/v/v) allowing small changes in its composition. Detection was at 314 mm. Rf values being 0.1-0.4, baseline resolution was achieved for tinidazole and the hydrolysis products. The analytes were stable on the sorbent and could be precisely and accurately measured in the range 20-170 ng per band.

High performance thin layer chromatographic analysis of hydrolyzed tinidazole solutions. II. Hydrolysis kinetics of tinidazole.

In a citrate-borate-phosphate buffer, 5 mM tinidazole solutions exhibited maximum stability stability around pH 4.0-5.0. The hydrolysis of tinidazole was mostly a first-order reaction. At pH 10.0 and 60-80 degrees C, tinidazole had an activation energy of 122 kJ mol-1 for hydrolysis. It was postulated that tinidazole decomposes by different mechanisms under basic and neutral/acidic conditions.

Simultaneous quantitative determination of metronidazole and nalidixic acid in tablets by difference spectroscopy.

A difference spectrophotometric procedure has been developed for simultaneous determination of metronidazole (MDZ) and nalidixic acid (NA) in tablets. The method comprised the measurement of the absorbance of a solution of the tablet extract in 0.1 M NaOH relative to that of an equimolar solution in 0.1 M HCl at 292 nm for NA and 325 nm for MDZ. The presence of identical isosbestic points for pure drug solutions and tablet extracts indicated the non-interference of excipients in the absorption at these wavelengths. Compliance with Beer's law was observed in the concentration ranges 5-25 micrograms ml(-1) for MDZ and 15-35 micrograms ml(-1) for NA these wavelengths.

Determination of nitroimidazole residues in poultry tissues, serum and eggs by high-performance liquid chromatography.

A simple high-performance liquid chromatographic (HPLC) method was developed for determination of dimetridazole and metronidazole residues in poultry muscle, liver, serum and eggs. The drug residues were extracted from tissues and egg samples with acetonitrile followed by solid-phase extraction clean-up and HPLC analysis with photodiode array detector. Serum samples were treated with trichloroacetic acid, centrifuged and analysed without further clean-up. The detection limits were 2 ng/g and 5 ng/mL of analysed tissue (egg) and serum samples, respectively. Average recoveries for spike levels of 10 and 20 ng/g ranged from 82 to 94%, and coefficients of variation were below 10%.

[Pharmacokinetics of the trichomonacidal agent ZK 25 095 in 6 normal subjects following intravenous and oral administration (author's transl)]. / Pharmakokinetik des Trichomonazidums ZK 25 095 bei 6 gesunden Probanden nach intravenöser und oraler Applikation

The distribution, absorption and elimination of 5-morpholinomethyl-3-(5-nitro-1-methyl-2-imidazolyl-methylene-amino)-2-oxazolidinone-hydrochloride (test designation ZK 25 095), which proved to be an effective trichomonacidal agent in animal and clinical trials, was determined microbiologically and with the aid of 14C-labelled substance. After i.v. injection of 10 mg ZK 25095 in each of two volunteers the substance was distributed between blood and body tissues within approximately 10 min. The calculated volume of distribution amounted to 70% of the body volume. After oral administration of 250 mg in tablet form to each of three volunteers the substance was almost completely absorbed within a few hours. The maximum blood level was reached 3 to 4 h after administration. It amounted to about 80% of the blood levels (distribution equilibrium) after i.v. administration. ZK 25 095 was eliminated from the body with a half-life of approximately 9 h. 3/4 of the elimination were effected via urine and 1/4 via the faeces. 30-50% of the radioactivity eliminated with urine originated from microbiologically active (trichomonacidal) substance.