Stability-indicating HPTLC determination of imatinib mesylate in bulk drug and pharmaceutical dosage form

Development of Green and High Throughput Microplate Reader-Assisted Universal Microwell Spectrophotometric Assay for Direct Determination of Tyrosine Kinase Inhibitors in Their Pharmaceutical Formulations Irrespective the Diversity of Their Chemical Structures

This study discusses the development and validation of a universal microwell spectrophotometric assay for TKIs, regardless of the diversity in their chemical structures. The assay depends on directly measuring the native ultraviolet light (UV) absorption of TKIs. The assay was carried out using UV-transparent 96-microwell plates and the absorbance signals were measured by a microplate reader at 230 nm, at which all TKIs had light absorption. Beer's law correlating the absorbances of TKIs with their corresponding concentrations was obeyed in the range of 2-160 µg mL^-1 with excellent correlation coefficients (0.9991-0.9997). The limits of detection and limits quantitation were in the ranges of 0.56-5.21 and 1.69-15.78 µg mL^-1, respectively. The proposed assay showed high precision as the values of the relative standard deviations for the intra- and inter-assay precisions did not exceed 2.03 and 2.14%, respectively. The accuracy of the assay was proven as the recovery values were in the range of 97.8-102.9% (±0.8-2.4%). The proposed assay was successfully applied to the quantitation of all TKIs in their pharmaceutical formulations (tablets) with reliable results in terms of high accuracy and precision. The assay greenness was evaluated, and the results proved that the assay fulfils the requirements of green analytical approach. The proposed assay is the first assay that can analyse all TKIs on a single assay system without chemical derivatization or modifications in the detection wavelength. In addition, the simple and simultaneous handling of a large number of samples as a batch using micro-volumes of samples gave the assay the advantage of high throughput analysis, which is a serious demand in the pharmaceutical industry.

Spectrophotometric Investigations of Charge Transfer Complexes of Tyrosine Kinase Inhibitors with Iodine as a σ-Electron Acceptor: Application to Development of Universal High-Throughput Microwell Assay for Their Determination in Pharmaceutical Formulations

Background and Objective: Tyrosine kinase inhibitors (TKIs) are used for the treatment of different types of cancers. The current study describes, for the first time, the ultraviolet-visible spectrophotometric investigation of charge transfer complexes (CTCs) of seven TKIs, as electron donors, and iodine, as σ-electron. Materials and Methods: The formation of CTCs was promoted in dichloromethane, among the other solvents used in the investigation. The molar absorptivity values, association constants, and free energy changes of the CTCs were determined. Stoichiometric ratio of TKI: iodine as well as TKIs site(s) of interaction were addressed. Reaction was the basis for constructing a novel simple and accurate 96-microwell spectrophotometric assay (MW-SPA) with high-throughput property for the quantitative determination of TKIs in their pharmaceutical formulations. Results: Beer's law, which relates CTC absorbances to TKI concentrations, was followed within the optimal range of 2 to 100 µg/well (r ranged from 0.9991 to 0.9998). Detection and quantification limits ranged from 0.91 to 3.60 and 2.76 to 10.92 g µmL^-1, respectively. Relative standard deviations values for the intra- and inter-assay precisions of the proposed MW-SPA did not exceed 2.13 and 2.34%, respectively. Studies of recovery demonstrated MW-SPA accuracy, with results ranging from 98.9% to 102.4%. All TKIs, both in bulk form and in pharmaceutical formulations (tablets), were effectively determined using the suggested MW-SPA. Conclusions: The current MW-SPA involved a simple procedure and it was convenient as it could analyse all proposed TKIs utilizing a single assay system at once measuring wavelengths for all TKIs. In addition, the proposed MW-SPA has high throughput which enables the processing of a batch of huge samples' number in very short reasonable time period. In conclusion, TKIs can be routinely analysed in their dosage forms in quality control laboratories, and the assay can be highly valuable and helpful in this regard.

Turn-off fluorescence of nitrogen and sulfur carbon quantum dots as effective fluorescent probes for determination of imatinib. Application to biological fluids

Nitrogen and sulfur carbon quantum dots(N,S-CQDs) as effective fluorescent nanoprobes were synthesized through one-step-hydrothermal method using thiosemicarbazide (as nitrogen and sulfur source) and citric acid (as carbon source). The highly fluorescent N,S-CQDs were subjected to various characterization techniques. The fluorescence of the synthesized N,S-CQDs is characterized by maximum fluorescence emission at 415 nm after excitation at 345 nm and a high quantum yield of 0.58. The native N,S-CQDs fluorescence is quantitatively quenched upon addition of imatinib (IMA), so they are used for its spectrofluorimetric determination in its pharmaceutical formulations and biological fluids. Under optimal conditions, N,S-CQDs exhibited a "turn-off" fluorescence response to IMA over the range of 1.0 to 15.0 µg/mL with a limit of quantification of 0.42 µg/mL and a lower detection limit of 0.14 µg/mL. Stern-Volmer equation was used to study the mechanism of quenching and it was found to occur through static quenching mechanism. The method was extended to the in-vitro determination of the drug in spiked human urine and plasma samples and the percent recoveries were satisfactory.

Spectrophotometric and computational investigations of charge transfer complexes of chloranilic acid with tyrosine kinase inhibitors and application to development of novel universal 96-microwell assay for their determination in pharmaceutical formulations

The tyrosine kinase inhibitors (TKIs) are chemotherapeutic drugs used for targeted therapy of various types of cancer. In literature, there is no existing universal chromogenic reagent used for development of spectrophotometric assay for all TKIs regardless the diversity of their chemical structures. This work discusses, for the first time, the experimental and computational evaluation of chloranilic acid (CLA) as a universal chromogenic reagent for developing a novel 96-microwell spectrophotometric assay (MW-SPA) for TKIs. The reaction of CLA with seven TKIs was examined in different organic solvents of various dielectric constants and polarity indexes. The reaction resulted in an instantaneous formation of intensely purple coloured products with all the investigated TKIs. Spectrophotometric investigations confirmed that the reactions proceeded via the formation of charge-transfer complexes (CTC). The physical parameters (molar absorptivity, molar ratio, association constant and standard free energy) were determined for the CTC of all TKIs. Computational calculations for the relative electron densities on each atom of the TKI molecule and molecular modelling for the CTC were conducted, and the site(s) of interaction on each TKI molecule were determined. Under the optimized conditions, Beer's law correlating the absorbances of the CTC with the concentrations of TKIs were obeyed in the range of 5-500 µg/well with good correlation coefficients (0.9991-0.9998). The limits of detection and quantitation were in the ranges of 1.89-5.09 and 5.74-15.42 µg/well, respectively. The proposed MW-SPA showed high precisions as the values of the relative standard deviations did not exceed 2.01 and 2.45% for the intra- and inter-assay precision, respectively. The accuracy of MW-SPA was proved by recovery studies as the recovery values were in the range of 98.8-103.7%. The proposed MW-SPA was successfully applied for the determination of all TKIs in their bulk forms and pharmaceutical formulations (tablets) with good accuracy and precisions. The proposed MW-SPA is the first assay that can analyse all the TKIs on a single assay system without modifications in the detection wavelength. Additional advantages of the proposed MW-SPA are simple, economic, and more importantly have high throughput. Therefore, the assay can be helpful and beneficial for routine analysis of TKIs in their pharmaceutical formulations in quality control laboratories.

Experimental and Computational Evaluation of Chloranilic Acid as an Universal Chromogenic Reagent for the Development of a Novel 96-Microwell Spectrophotometric Assay for Tyrosine Kinase Inhibitors

The tyrosine kinase inhibitors (TKIs) are chemotherapeutic drugs used for the targeted therapy of various types of cancer. This work discusses the experimental and computational evaluation of chloranilic acid (CLA) as a universal chromogenic reagent for developing a novel 96-microwell spectrophotometric assay (MW-SPA) for TKIs. The reaction resulted in an instantaneous formation of intensely purple colored products with TKIs. Spectrophotometric results confirmed that the reactions proceeded via the formation of charge-transfer complexes (CTCs). The physical parameters were determined for the CTCs of all TKIs. Computational calculations and molecular modelling for the CTCs were conducted, and the site(s) of interaction on each TKI molecule were determined. Under the optimized conditions, Beer's law correlating the absorbances of the CTCs with the concentrations of TKIs were obeyed in the range of 10-500 µg/well with good correlation coefficients (0.9993-0.9998). The proposed MW-SPA fully validated and successfully applied for the determination of all TKIs in their bulk forms and pharmaceutical formulations (tablets). The proposed MW-SPA is the first assay that can analyze all the TKIs on a single assay system without modifications in the detection wavelength. The advantages of the proposed MW-SPA are simple, economic and, more importantly, have high throughput.

Quantification of febuxostat polymorphs using powder X-ray diffraction technique

Febuxostat is a pharmaceutical compound with more than 20 polymorphs of which form A is most widely used and usually exists in a mixed polymorphic form with form G. In the present study, a quantification method for polymorphic form A and form G of febuxostat (FEB) has been developed using powder X-ray diffraction (PXRD). Prior to development of a quantification method, pure polymorphic form A and form G are characterized. A continuous scan with a scan rate of 3° min(-1) over an angular range of 3-40° 2θ is applied for the construction of the calibration curve using the characteristic peaks of form A at 12.78° 2θ (I/I0100%) and form G at 11.72° 2θ (I/I0100%). The linear regression analysis data for the calibration plots shows good linear relationship with R(2)=0.9985 with respect to peak area in the concentration range 10-60 wt.%. The method is validated for precision, recovery and ruggedness. The limits of detection and quantitation are 1.5% and 4.6%, respectively. The obtained results prove that the method is repeatable, sensitive and accurate. The proposed developed PXRD method can be applied for the quantitative analysis of mixtures of febuxostat polymorphs (forms A and G).

Imatinib mesylate

Imatinib (INN), marketed by Novartis as Gleevec (United States) or Glivec (Europe/Australia/Latin America), received Food & Drug Administration (FDA) approval in May 2001 and is a tyrosine kinase inhibitor used in the treatment of multiple cancers, most notably Philadelphia chromosome-positive (Ph+) chronic myelogenous leukemia. Like all tyrosine kinase inhibitors, imatinib works by preventing a tyrosine kinase enzyme. Because the BCR-Abl tyrosine kinase enzyme exists only in cancer cells and not in healthy cells, imatinib works as a form of targeted therapy-only cancer cells are killed through the drug's action. In this regard, imatinib was one of the first cancer therapies to show the potential for such targeted action and is often cited as a paradigm for research in cancer therapeutics. This study presents a comprehensive profile of imatinib, including detailed nomenclature, formulae, physico-chemical properties, methods of preparation, and methods of analysis (including compendial, electrochemical, spectroscopic, and chromatographic methods of analysis). Spectroscopic and spectrometric analyses include UV/vis spectroscopy, vibrational spectroscopy, nuclear magnetic resonance spectrometry ((1)H and (13)C NMR), and mass spectrometry. Chromatographic methods of analyses include electrophoresis, thin layer chromatography, and high-performance liquid chromatography. Preliminary stability investigations for imatinib have established the main degradation pathways, for example, oxidation to N-oxide under oxidative stress conditions. Stability was also carried out for the formulation by exposing to different temperatures 0°C, ambient temperature, and 40°C. No remarkable change was found in the drug content of formulation. This indicates that the drug was stable at the above optimized formulation. Stability studies under acidic and alkaline conditions have established the following main degradation products: α-(4-Methyl-1-piperazinyl)-3'-{[4-(3-pyridyl)-2-pyrimidinyl] amino}-p-tolu-p-toluid-ide methanesulfonate and 4-(4-methylpiperazin-1-ylmethyl)-benzoic acid. The main degradation products under oxidation conditions, that is, 4-[(4-methyl-4-oxido-piperazin-1-yl)-methyl]-N-[4-methyl-3-(4-pyridin-3-yl-pyrimidin-2-ylamino)-phenyl]-enzamide, 4-[(4-methyl-1-oxido-piperazin-1-yl)-methyl]-N-[4-methyl-3-(4-pyridin-3-yl-pyrimidin-2-ylamino)-phenyl]-benzamide, and 4-[(4-methyl-1,4-dioxido-piperazin-1-yl)-methyl]-N-[4-methyl-3-(4-pyridin-3-yl-pyrimidin-2-ylamino)-phenyl]-enzamide. Clinical application studies for pharmacodynamics, pharmacokinetics, mechanism of action, and clinical uses of the drug were also presented. Each of the above stages includes appropriate figures and tables. More than 50 references were given as proof of the above-mentioned studies.

Quantitative determination of imatinib stability under various stress conditions

OBJECTIVE

A simple, rapid, reverse phase and stability-indicating high-performance liquid chromatography (HPLC) method for the estimation of imatinib in solution and in plasma under forced degradation conditions was developed.

MATERIALS AND METHODS

The method employed isocratic elution using a Waters Atlantis C18 (5 μ, 4.6 mm × 150 mm) HPLC column. The mobile phase consisted of acetonitrile and 10 mM KH2PO4 buffer in the ratio of 35:65 (v/v, pH = 4.6), which was delivered using isocratic flow at a rate of 1 mL/min. The injection volume of 50 μL and imatinib was monitored using UV detection 270 nm after a clean-up step with diethyl ether and with a total run time of 6 min.

RESULTS

The method was validated in solution as well as in plasma, and the response was found to be linear in the concentration range of 0.5-20 μg/mL. The coefficient of correlation was found to be >0.99. Forced degradation studies revealed that imatinib undergoes degradation under different stress conditions.

DISCUSSION

The developed HPLC method could effectively resolve degradation product peaks from imatinib except at neutral pH. Further, no interference was found at the retention time of imatinib from any plasma components, indicating selectivity of the developed method. The limits of detection and quantitation of the method were 0.025 and 0.5 μg/mL, respectively.

Stress Degradation Assessment of Lamotrigine Using a Validated Stability-Indicating HPTLC Method

In this work, a sensitive and stability-indicating HPTLC method for the determination of lamotrigine is presented. According to the International Conference on Harmonization guidelines Q1A, lamotrigine was exposed to a variety of stress conditions; these include heating in acidic, basic and neutral media. Its stability towards oxidative stress, humidity, high temperature and direct sunlight was also examined. Separation of the drug from its forced degradation impurities was achieved using TLC silica gel plates and a mobile phase composed of ethyl acetate: methanol: ammonia. The linear regression analysis of the data obtained for the correlation plots showed good linearity over the concentration range of 10–300 ng/spot. The forced degradation studies showed that lamotrigine is susceptible to degradation under acidic, basic, neutral and oxidative conditions, among which alkaline-induced hydrolysis had the highest degradative potential. Alternatively, the drug was stable under heat, humidity, and daylight stress factors. In order to assess the purity and stability of the drug in tablet formulations, the developed method was applied to the analysis of commercial tablets in brand and generic products. The obtained results showed that the degradation of the drug has not occurred in the marketed formulations that were analyzed by the described methodology.

A HPTLC densitometric method for the determination of aloeverose in Aloe vera gel

Aloe vera gel is a familiar ingredient in a range of widely available and advertisement healthcare and cosmetic products. As to date there are no documented reports on the standardization of A. vera gel and the following study is an attempt in this direction. A. vera gel was evaluated for its aloeverose content for the first time. Aloeverose, was separated on a thin-layer of silica gel by isocratic gradient elution technique was determined by using HPTLC-photodensitometry. The proposed method is simple and sensitive and can be used for the routine assay of aloeverose in phytomedicines containing A. vera gel.