Solid-phase extraction and HPTLC determination of isoniazid and acetylisoniazid in serum. Comparison with HPLC

A new solid-phase extraction (SPE) and quantitative determination of isoniazid (INH) and its acetyl metabolite (AcINH) in serum by high-performance thin-layer chromatography (HPTLC) is presented. Alkalized serum samples with nicotinamide as an internal standard are applied to an SPE cartridge containing a new SPE sorbent, [poly (divinylbenzene-co-N-vinylpyrrolidone )]. A simple procedure of conditioning, washing, and eluting steps is described. After evaporation of the eluates to dryness and reconstitution, one-dimensional HPTLC is performed on silica gel plates with ethyl acetate-methanol (70:30) as a mobile phase. Quantitation is done by densitometry. Convenient validation parameters are obtained (linearity, limits of detection and quantitation, precision, and accuracy) for INH and AcINH. The method is compared with a high-performance liquid chromatographic (HPLC) technique developed in the laboratory, and satisfactory correlation is found between data from the two techniques. The HPTLC method is sensitive and specific and is used to quantitate INH and AcINH in patient blood serum, and the results are compared with those obtained by HPLC.     

Polarographic determination of isoniazide, N-acetylisoniazide and isonicotinic acid by superimposed sinusoidal tension]

The a.c. polarographic determination of isoniazid (INH), N-acetylisoniazid (AcINH) and isonicotinic acid (INA) is described. Under the optimal conditions of pH, ionic strength and electrical parameters, the limits of detection are 0.5 μg ml^-1 for AcINH, 0.2 μg ml^-1 for INH, and 0.03 μg ml^-1 for INA.     

Spectrophotometric determination of isoniazid with sodium 1,2-naphthoquinone-4-sulphonate and cetyltrimethyl ammonium bromide

A rapid, sensitive and simple spectrophotometric method is developed for the determination of isoniazid (INH) with sodium 1,2-naphthoquinone-4-sulphonate and cetyltrimethyl ammonium bromide (CTA) in alkaline medium. Beer's law is obeyed in the range of INH concentrations of 2-5.6 mug ml(-1) at the maximum absorption of 500 nm. Sensitivity is enhanced by the addition of CTA. The method is successfully employed for the determination of INH in various pharmaceutical preparations and common excipients used as additives in pharmaceuticals do not interfere in the proposed method.     

Superoxide reactivity of KatG: insights into isoniazid resistance pathways in TB

To gain insight into the mechanism of INH activation by KatG and to understand how resistance is conferred by the single active-site point mutation of KatG(S315T), we have employed pulse radiolysis as the means to initiate a catalytic pathway capable of mimicking the in vivo oxidation of isoniazid (INH). Radiolysis of a solution containing WT KatG revealed two intermediates: compound III (oxyferrous KatG) [415 (Soret), 545, 580 nm] formed [k1 = (4.47 +/- 0.91) x 105 M-1 s-1] in the absence of INH and compound II (410 (Soret), 540, 575 nm) formed [k1 = (4.43 +/- 0.69) x 105 M-1 s-1] in the presence of INH, with a comparison of the rates suggesting that compound III (rate-limiting) precedes compound II formation. By contrast, radiolysis of KatG(S315T) only led to compound III formation, whether INH was present [k1 = (4.72 +/- 0.99) x 105 M-1 s-1] or not [k1 = (4.51 +/- 1.38) x 105 M-1 s-1]. HPLC studies to determine the rates of INH-NADH adduct formation (an inhibitor of InhA) as catalyzed by KatG were also performed employing various oxidants: air [WT: (7.18 +/- 1.25) x 10-4, S315T: (0.74 +/- 0.39) x 10-4], superoxide (SOTS-1) [WT: (9.22 +/- 1.10) x 10-4, S315T: not detected], and tert-butylhydroperoxide [WT: (20.5 +/- 1.13) x 10-4, S315T: (10.15 +/- 0.19) x 10-4]. Taken together, the results from the pulse radiolysis work as well as the InhA inhibitor studies allow us to propose a mechanism capable of correlating the inability for the oxyferrous intermediate of KatG(S315T) to oxidize ("activate") INH to the suppressed formation of the INH-NADH adduct, thereby leading to INH resistance in Mycobacterium tuberculosis.     

Sensitive indirect spectrophotometric determination of isoniazid

A simple, rapid, sensitive and accurate indirect spectrophotometric method for the microdetermination of isoniazid (INH) in pure form and pharmaceutical formulations is developed. The procedure is based on the reaction of copper(II) with isoniazid in the presence of neocuproine (NC). In the presence of neocuproine, copper(II) is reduced easily by isoniazid to a Cu(I)-neocuproine complex, which shows an absorption maximum at 454 nm. By measuring the absorbance of the complex at this wavelength, isoniazid can be determined in the range 0.3-3.5 microgml-1. This method was applied to the determination of isoniazid in pharmaceutical formulation and enabled the determination of the isoniazid in microgram quantities (0.3-3.5 microgml-1). The results obtained for the assay of pharmaceutical preparations compared well with those obtained by the official method and demonstrated good accuracy and precision.     

Electrochemical oxidation of isoniazid catalyzed by (FcM)TMA at the platinum electrode and its practical analytical application

The electrocatalytic oxidation of isoniazid (INH) by (ferrocenylmethyl)trimethylammonium [(FcM)TMA] at the platinum electrode in 0.10 M Na₂SO₄ aqueous solution was studied by cyclic voltammetry (CV). Although INH itself showed a very poor electrochemical response at the platinum electrode, the response could be greatly enhanced by using (FcM)TMA as a mediator, which enables a sensitive electrochemical determination of the substrate INH. The reaction rate constant for catalytic oxidation reaction was evaluated as (3.98±0.10)×10³ M⁻¹ s⁻¹ by using chronoamperometry (CA). Experimental conditions such as supporting electrolyte and its concentration, solution pH, and the concentrations of the catalyst (FcM)TMA and the substrate INH were investigated to maximize the current efficiency of the electrocatalytic oxidation. The method can be used for the sensitive practical determination of INH, and also opens an avenue for using (FcM)TMA as a mediator in electroanalytical determination which is very simple, cheap, and rapid. Furthermore, no sample pretreatment or time-consuming extraction steps are required prior to the analysis.     

Determination of isoniazid concentration in rabbit vertebrae by isotope tracing technique in conjunction with HPLC

Medications compounded with isoniazid (INH) are usually applied to surgical sites at the completion of surgery to locally kill postoperative residual tubercle bacilli. However, the distribution and elimination of INH in the vertebrae in vivo are not known. In this study, isotope tracing was used in conjunction with high‐pressure liquid chromatography (HPLC) to address this. INH and technetium‐99 m‐labeled INH were applied to the vertebrae of rabbits. After 2 and 6 h, osseous tissues containing INH, as determined by radionuclide imaging, were collected for detection with HPLC. The results showed that INH mainly stayed around the vertebrae 6 h after its application and did not permeate widely into the blood or other organs, except for the kidneys. The standard deviations of INH concentrations in the technetium‐99 m‐INH group were approximately four‐fold smaller than those in the INH group. This method of coupling isotope tracing and HPLC can effectively limit experimental error during sample collection, allowing accurate and reliable identification of the concentration levels of INH in osseous tissues in vivo. Copyright © 2013 John Wiley & Sons, Ltd.     

A sensitive and specific method for isoniazid determination based on selective adsorption using an isoniazid ion-selective piezoelectric sensor

A selective, sensitive and simple ion-selective piezoelectric (ISP) sensor was developed for the direct determination of isoniazid (INH) in body fluids. Based on sensitive mass response of piezoelectric quartz crystal and selective adsorption/desorption across the modified film, the ISP sensor was fabricated by coating a PVC film containing activant on one electrode of a thickness-shear mode piezoelectric quartz crystal. The observed frequencies of ISP sensor were found to decrease with the increase of the INH concentration in a 0.1 M NaNO(3) solution. In this paper, three activants, INH-phosphotungstate (I), INH-silicotungstate (II), and INH-[BiI(4)](-) (III), were synthesized and investigated. Calibration graphs were linear from 6x10(-8) to 2x10(-3) M for I, 2x10(-7) to 2x10(-3) M for II and 2x10(-7) to 2x10(-3) M for III, with detection limits 6x10(-8) M for I, 2x10(-7) M for II and 2x10(-7) M for III, in a 0.1 M NaNO(3) solution at pH 7.0 and 37 degrees C. Recoveries were from 98% to 102% with R.S.D. up to 2%. Results for real samples obtained by the proposed method agreed well with those obtained by the conventional pharmacopeia method.     

Optimized determination of thiochrome derivatives of thiamine and thiamine phosphates in whole blood by reversed-phase liquid chromatography with precolumn derivatization

A liquid chromatographic method involving precolumn derivatization for determining thiamine and its phosphate esters in human blood has been optimized. Blood sample stored at - 20 degrees C were haemolysed and deproteinized by perchloric acid. The supernatants of the samples were oxidized by addition of potassium ferricyanide-sodium hydroxide, and phosphoric acid was added to obtain a neutral pH in order to extend the column life. The samples were stable after derivatization for at least 24 h, if protected from light and kept at room temperature. Gradient separation with 140 mmol phosphate buffer (pH 7.0), and methanol, tert-butylammonium hydroxide and dimethylformamide as modifiers, on a 3-microns Chromsphere octadecylsilica column gave an analysis time of 15 min. The method was found to be very suitable for the determination of thiamine components in whole blood. The minimal detectable amount is 0.5 nmol/l and the method is linear to at least 1000 nmol/l. The recovery (98 +/- 3%) and precision are very good.     

A liquid chromatography/tandem mass spectrometry method for the simultaneous quantification of isoniazid and ethambutol in human plasma

Isoniazid and ethambutol are commonly used in various combination treatments for tuberculosis, and for this reason a rapid and sensitive liquid chromatography/tandem mass spectrometry (LC/MS/MS) method was developed and validated for simultaneous quantification of these two drugs in human plasma. After a simple protein precipitation using methanol, the analytes and the internal standard metformin were chromatographed on a C18 column and detected by MS/MS. An atmospheric pressure chemical ionization interface was chosen to reduce ion suppression from sample matrix components and provide high sensitivity. The LC retention times for isoniazid and ethambutol were 2.46 and 2.27 min, respectively. The method was linear in the concentration range of 10.0-5000 ng/mL for each analyte using 100 microL plasma. The intra- and inter-day precisions, expressed as the relative standard deviation (RSD), were less than 5.7 and 6.4%, determined from QC samples for isoniazid and ethambutol, and the accuracies were within +/-2.1% and +/-4.5% in terms of relative error, respectively. The method was successfully employed in a pharmacokinetic study after oral administration of a multicomponent formulation containing 150 mg isoniazid, 500 mg ethambutol, 150 mg rifampicin and 250 mg pyrazinamide.     

Voltammetric assay of rifampicin and isoniazid drugs, separately and combined in bulk, pharmaceutical formulations and human serum at a carbon paste electrode

The electrochemical oxidation of both the rifampicin (RIF) and isoniazid (INH) drugs has been investigated by cyclic and square-wave voltammetry in Britton-Robinson buffers (pH 2-11) at a carbon paste electrode. The oxidation of rifampicin generated a well-defined pH-dependent quasi-reversible anodic-cathodic peak couple corresponding to a mechanism involving the transfer of two electrons/two protons, typical to that of hydroquinones, in addition to an irreversible anodic peak at a more positive potential which may be due to the oxidation of phenolic hydroxyl group. For the isoniazid, an irreversible anodic peak was observed, which may be attributed to the irreversible oxidation of the amide moiety of the drug molecule. A validated square-wave adsorptive anodic stripping voltammetric procedure was described to assay the two drugs separately or combined in pharmaceutical formulations and human serum. The recoveries of RIF in rimactane^® capsules (300 mg RIF) and INH in isocid^® tablets (200 mg INH) were found to be 98.57±0.81% and 100.57±0.74%, respectively. The proposed procedure was also successfully applied to simultaneous assay of rifampicin and isoniazid drugs combined in rimactazid tablets (150 mg INH+300 mg RIF) with recoveries of 98.79±0.97% and 99.54±0.74%, respectively, without the necessity for sample pretreatment or time-consuming extraction steps prior to the analysis. The results were favorably compared to those obtained by the reported USP method. Moreover, the proposed procedure was successfully applied to simultaneous assay of both drugs in human serum samples with limits of detection and quantitation of 5×10⁻⁸ and 1.7×10⁻⁷ M for RIF and 6.1×10⁻⁸ and 2×10⁻⁷ M for INH.     

Synthesis and antitubercular activity of substituted novel pyrazoline derivatives

A series of 2-2-methoxy-4-[5-(substituted phenyl)1-(4-pyridylcarbonyl)-4,5-dihydro-1H-3-pyrazolyl] phenoxyacetic acid were synthesized by the reaction between isoniazid (INH) and chalcones, and were tested for their antimycobacterial activity in vitro against Mycobacterium tuberculosis H37Rv and INH resistant M. tuberculosis using BACTEC-460 radiometric system and agar dilution method. Among the synthesized compounds, Compounds II 2-4-[5-(4-hydroxyphenyl)-1-(4-pyridylcarbonyl)-4,5-ihydro-1H-3-pyrazolyl]-2-methoxy phenoxy acetic acid was found to be most active agent against M. tuberculosis H37Rv (MTB) and INH resistant M. tuberculosis (INHR-MTB), with minimum inhibitory concentration of 0.12 microM, when compared to INH 5.6-fold more active against MTB and 78-fold more active against INHR-MTB, respectively.     

Application of Near Infrared Diffuse Reflectance Spectroscopy with Radial Basis Function Neural Network to Determination of Rifampincin Isoniazid and Pyrazinamide Tablets

Partial least squares(PLS),back-propagation neural network(BPNN)and radial basis function neural network(RBFNN)were respectively used for estalishing quantative analysis models with near infrared(NIR)diffuse reflectance spectra for determining the contents of rifampincin(RMP),isoniazid(INH)and pyrazinamide(PZA)in rifampicin isoniazid and pyrazinamide tablets.Savitzky-Golay smoothing,first derivative,second derivative,fast Fourier transform(FFT)and standard normal variate(SNV)transformation methods were applied to pretreating raw NIR diffuse reflectance spectra.The raw and pretreated spectra were divided into several regions,depending on the average spectrum and RSD spectrum.Principal component analysis(PCA)method was used for analyzing the raw and pretreated spectra in different regions in order to reduce the dimensions of input data.The optimum spectral regions and the models' parameters were chosen by comparing the root mean square error of cross-validation(RMSECV)values which were obtained by leave-one-out cross-validation method.The RMSECV values of the RBFNN models for determining the contents of RMP,INH and PZA were 0.00288,0.00226 and 0.00341,respectively.Using these models for predicting the contents of INH,RMP and PZA in prediction set,the RMSEP values were 0.00266,0.00227 and 0.00411,respectively.These results are better than those obtained from PLS models and BPNN models.With additional advantages of fast calculation speed and less dependence on the initial conditions,RBFNN is a suitable tool to model complex systems.     

Simple Sensitive Spectrophotometric Determination of Isoniazid and Ritodrine Hydrochloride

A novel coupling reagent was used for simple, rapid, and sensitive spectrophotometric determination of isoniazid (1NH) and ritodrine hydrochloride (RTH) in pure form or in pharmaceutical preparations of it. The method is based on the diazotization of 4,4-methylene-bis-m-nitroaniline followed by a coupling reaction with either INH or RTH in hydrochloric acid medium. The resulting colored products have absorption maxima at 495 and 473 nm, respectively. Beer's law is obeyed in the concentration ranges of 0.1–15 μg/mL and 0.1–17 μg/mL. The method is applied for the analysis of INH/RTH in pharmaceutical preparations and the results agree favorably with the official and reported data. Common excipients used as additives in pharmaceuticals do not interfere in the proposed method. The method offers the advantages of simplicity, rapidity, and sensitivity without the need of extraction or heating. __________ From Zhurnal Analiticheskoi Khimii, Vol. 60, No. 9, 2005, pp. 927–932. Original English Text Copyright ? 2005 by Krishnamurthy Naidu, Suvardhan, Suresh Kumar, Rekha, Sastry, Chiranjeevi. Thee text was submitted by the authors in English.     

The nonenzymatic activation of isoniazid by MnIII-pyrophosphate in the presence of NADH produces the inhibition of the enoyl-ACP reductase InhA from Mycobacterium tuberculosis

The antituberculosis drug isoniazid (INH) is quickly oxidized by stoichiometric amounts of manganese(III)-pyrophosphate. In the presence of the nicotinamide coenzyme, the INH oxidation produced the formation of INH-NAD(H) adducts and allowed the in vitro inhibition of the enoyl-acyl carrier protein reductase InhA, an INH target in the biosynthetic pathway for mycolic acids. Manganese(III)-pyrophosphate is an efficient alternative oxidant to mimic the activity of the Mycobacterium tuberculosis KatG catalase-peroxidase and will be useful for further mechanistic studies of INH activation and for structural investigations on reactive INH species and resulting InhA inhibitors.     

High-performance liquid chromatographic determination of bromazepam in human plasma

An assay using high-performance liquid chromatography has been developed for the determination of bromazepam in plasma. After a single-step extraction from basified samples with dichloromethane, using decarboxyloflazepate as an internal standard, samples were analysed using a reversed-phase Nova Pak 5-microns column with a mobile phase of methanol - phosphate buffer (60 + 40) adjusted to pH 7.6. The drugs were detected at 239 nm and the limit of detection was found to be 3 micrograms l-1 for bromazepam. The method is simple, rapid and sensitive and permits bromazepam levels in clinical and pharmacokinetic studies to be monitored.     

Optimization of a stability-indicating HPLC method for the simultaneous determination of rifampicin, isoniazid, and pyrazinamide in a fixed-dose combination using artificial neural networks

The aim of this study is to develop and optimize a simple and reliable high-performance liquid chromatography (HPLC) method for the simultaneous determination of rifampicin (RIF), isoniazid (INH), and pyrazinamide (PZA) in a fixed-dose combination. The method is developed and optimized using an artificial neural network (ANN) for data modeling. Retention times under different experimental conditions (solvent, buffer type, and pH) and using four different column types (referred to as the input and testing data) are used to train, validate, and test the ANN model. The developed model is then used to maximize HPLC performance by optimizing separation. The sensitivity of the separation (retention time) to the changes in column type, concentration, and type of solvent and buffer in the mobile phase are investigated. Acetonitrile (ACN) as a solvent and tetrabutylammonium hydroxide (tBAH), used to adjust pH, have the greatest influence on the chromatographic separation of PZA and INH and are used for the final optimization. The best separation and reasonably short retention times are produced on the micro-bondapak C18, 4.6 x 250-mm column, 10 microm/125 A using ACN-tBAH (42.5:57.5, v/v) (0.0002M) as the mobile phase, and optimized at a final pH of 3.10.     

反相高效液相法测定血浆及尿液中的异烟肼

 建立了血浆及尿液中异烟肼的高效液相快速测定方法 ,以满足临床药物分析和法医学鉴定的需要 ,提高对血浆及尿液中异烟肼浓度检测的准确性。以香草醛为衍生化试剂 ,将异烟肼经柱前衍生为异烟肼 香草醛腙 ,直接对处理后样品中的腙进行定性、定量分析。以在空白人体液样本中定量添加标准异烟肼的方法考察了样品的前处理方法、仪器条件、线性范围、精密度、回收率等 ,并对健康受试者血液中的异烟肼浓度进行了监测。结果表明 ,方法的线性范围为 0 2mg/L～ 1 2 0mg/L ;检测限为 0 2mg/L ;日内、日间精度均小于 4 0 % (n =5) ;回收率在96 3 %以上。     

Evaluation of the pH- and thermal stability of the recombinant green fluorescent protein (GFP) in the presence of sodium chloride

The thermal stability of recombinant green fluorescent protein (GFP) in sodium chloride (NaCl) solutions at different concentrations, pH, and temperatures was evaluated by assaying the loss of fluorescence intensity as a measure of denaturation. GFP, extracted from Escherichia coli cells by the three-phase partitioning method and purified through a butyl hydrophobic interaction chromatography (HIC) column, was diluted in water for injection (WFI) (pH 6.0-7.0) and in 10 mM buffer solutions (acetate, pH 5.0; phosphate, pH 7.0; and Tris-EDTA, pH 8.0) with 0.9-30% NaCl or without and incubated at 80-95 degrees C. The extent of protein denaturation was expressed as a percentage of the calculated decimal reduction time (D-value). In acetate buffer (pH 4.84+/-0.12), the mean D-values for 90% reduction in GFP fluorescence ranged from 2.3 to 3.6 min, independent of NaCl concentration and temperature. GFP thermal stability diluted in WFI (pH 5.94+/-0.60) was half that observed in phosphate buffer (pH 6.08+/-0.60); but in both systems, D-values decreased linearly with increasing NaCl concentration, with D-values (at 80 degrees C) ranging from 3.44, min (WFI) to 6.1 min (phosphate buffer), both with 30% NaCl. However, D-values in Tris-EDTA (pH 7.65+/-0.17) were directly dependent on the NaCl concentration and 5-10 times higher than D-values for GFP in WFI at 80 degrees C. GFP pH- and thermal stability can be easily monitored by the convenient measure of fluorescence intensity and potentially be used as an indicator to monitor that processing times and temperatures were attained.     

采用甲基丙烯酸丁酯整体微柱芯片系统测定血样中痕量异烟肼

将合成的甲基丙烯酸丁酯(BMA)整体柱与微流控芯片技术结合,在PMMA芯片上以K3Fe(CN)6-NaOH-异烟肼化学发光体系为样品对象,在优化混合发光试剂比例和流速以及选择适合的洗脱液基础之上,实现了BMA整体微柱对异烟肼样品的富集作用,平均富集倍数和回收率分别达到16.8和84.2%,由此建立了流动注射化学发光(FIA-CL)芯片系统测定血液中痕量异烟肼的浓度的方法,可有效地实现异烟肼血药浓度分析的片上预处理和快速测定,检出限低于0.2 mg/L。