Mona M. Al-Shehri

Capillary Electrophoretic Determination of Antimigraine Formulations Containing Caffeine, Ergotamine, Paracetamol and Domperidone or Metoclopramide

A novel, fast, sensitive and specific technique using capillary electrophoresis coupled to a diode array detector has been developed for the separation and simultaneous determination of two antimigraine mixtures in tablet formulation. The two combinations are ergotamine tartrate (ERG), caffeine (CAF) and paracetamol (PAR) with either domperidone (DOM), combination (I) or metoclopramide (MET), combination (II). The proposed method utilized a fused silica capillary (55 cm × 75 µm i.d.) and background electrolyte composed of phosphate buffer (25 mM, pH 9.8). The separation was achieved at 20 KV applied voltage and at 25°C. The described method was linear over the range of 1-80 and 2-100 µg/mL for CAF and MET, respectively, and 1-80 µg/mL for DOM, ERG and PAR. Intra-day and inter-day relative standard deviation (n = 5) was ≤1.10%. The limits of detection of CAF and PAR were 0.20 and 0.10 µg/mL, respectively, and 0.50 µg/mL for MET, DOM and ERG. Other aspects of analytical validation were also evaluated. The proposed method was successfully applied to the analysis of the two combinations in their tablets. Therefore, the proposed method is suitable for the routine control of these ingredients in multicomponent dosage forms.

3-(Adamantan-1-yl)-4-(prop-2-en-1-yl)-1H-1,2,4-triazole-5(4H)-thione.

The title molecule, C15H21N3S, exists as the thione tautomer in the solid state. The 1,2,4-triazole ring is almost planar (r.m.s. deviation = 0.004 Å) and the prop-2-en-1-yl chain is close to being perpendicular to this plane [C—N—C—C torsion angle = 77.1 (5)°]. In the crystal, centrosymmetric dimeric aggregates are formed by pairs of N—H⋯S hydrogen bonds as parts of eight-membered (⋯HNCS)2 synthons. These are connected into layers parallel to (101) via C—H⋯π interactions, where the π-system is the triazole ring. The investigated sample was a nonmerohedral twin; the refined domain ratio was 0.655 (4):0.345 (4).

Derivative emission spectrofluorimetry for the simultaneous determination of guaifenesin and phenylephrine hydrochloride in pharmaceutical tablets

Rapid, simple and sensitive derivative emission spectrofluorimetric methods have been developed for the simultaneous analysis of binary mixtures of guaifenesin (GUA) and phenylephrine hydrochloride (PHE). The methods are based upon measurement of the native fluorescence intensity of the two drugs at λex = 275 nm in methanolic solutions, followed by differentiation using first (D1) and second (D2) derivative techniques. The derivative fluorescence intensity-concentration plots were rectilinear over a range of 0.1-2 µg/mL for both GUA and PHE. The limits of detection were 0.027 (D1, GUA), 0.025 (D2, GUA), 0.031 (D1, PHE) and 0.033 (D2, PHE) µg/mL and limits of quantitation were 0.089 (D1, GUA), 0.083 (D2, GUA), 0.095 (D1, PHE) and 0.097 (D2, PHE) µg/mL. The proposed derivative emission spectrofluorimetric methods (D1 and D2) were successfully applied for the determination of the two compounds in binary mixtures and tablets with high precision and accuracy. The proposed methods were fully validated as per ICH guidelines.

Direct Enantiomeric Resolution of Betaxolol with Application to Analysis of Pharmaceutical Products

Background: We have recently developed a new technique for quantitatively measuring protein-bound 3-nitrotyrosine (3-NT), a footprint of nitrosative stress, utilizing high-performance liquid chromatography with an electrochemical detection (HPLC-ECD) system. Using this system, we showed that 3-NT formation was upregulated in the sputum of both COPD and asthmatic patients. However, in order to improve the accuracy of the measurement system, We have to resolve some problems which were the influence of free amino acid form of 3-NT and of salivary contamination. Objectives: We initially investigated the amount of the free amino acid form of 3-NT in induced sputum and compared with that of protein-bound 3-NT. Next, we evaluated the concentration of protein-bound 3-NT in saliva and compared with that in induced sputum by means of HPLC-ECD. Methods: Five male COPD patients were enrolled. Induced sputum and saliva were obtained from the patients. The free amino acid form of 3-NT in sputum and saliva was measured by HPLC-ECD, and the protein-bound 3-NT and tyrosine in sputum and saliva were enzymatically hydrolyzed by Streptomyces griseus Pronase and measured for the protein hydrolysate by HPLC-ECD. Results: The mean value of the amount of protein-bound 3-NT was 65.0 fmol (31.2 to 106.4 fmol). On the other hand, the amount of the free amino acid form of 3-NT was under the detection limit (<10 fmol). The levels of both 3-NT (sputum: 0.55 ± 0.15 pmol/ml, saliva: 0.02 ± 0.01 pmol/ml, p < 0.01) and tyrosine (sputum: 0.81 ± 0.43 μmol/ml, saliva: 0.07 ± 0.04 μmol/ml, p < 0.01) in saliva were significantly lower than in sputum. The percentage of 3-NT in saliva to that in sputum was about 3.1%, and that of tyrosine was about 9.0%. Conclusion: The free amino acid form of 3-NT does not affect the measurement of protein-bound 3-NT. Furthermore, the influence of salivary contamination on the measurement of protein-bound 3-NT in induced sputum by means of HPLC-ECD was very small and could be negligible.A protein digestion system using immobilized enzymes for protein identification and glycochain analyses has been developed, and a vibration reaction unit for micro-scale sample convection on an enzyme-immobilized solid surface was constructed. BSA as a model substrate was digested by this unit, and was successfully identified by mass spectrometry (MS) analyses. Compared to the conventional liquid-phase digestion, the reaction unit increased the number of matched peptides from 9 to 26, protein score from 455 to 1247, and sequence coverage from 21% to 48%. Glycopeptidase F (NGF), an enzyme that cleaves N-glycans from glycoproteins, was also immobilized and used to remove the glycochains from human immunoglobulin G (IgG). Trypsin and NGF were immobilized on the same solid surface and used to remove glycochains from IgG in single-step. Glycochains were labeled with fluorescent reagent and analyzed by HPLC. Several peaks corresponding to the glycochains of IgG were detected. These results suggested that the single-step digestion system, by immobilized multiple enzymes (trypsin and NGF) would be effective for the rapid structural analysis of glycoproteins.This research shows a novel method for hazard identification of a chemical and UV light on a single cell level with a laser probe beam. The laser probe beam was passed through interface of cell membrane/culture medium of a cultured human hepatoblastoma cell line HepG2. Deflection of the laser probe beam, which was induced by changes in concentration gradients due to the active materials movement across the cell membrane, was monitored. When a toxic hazard existed, a living cell was expected to be killed or injured, or cellular behaviors to be changed greatly. Then, the changing deflection signal from the living cell would become unchanged or altered in a different way. This was successfully demonstrated with cytotoxity of UV light and H2O2. Most of the cultured HepG2 cells showed changing deflection signals after 10 min illumination of UV-visible light longer than 370 nm, while almost all HepG2 cells showed unchanged deflection signal after 10 min illumination of UV-visible light with wavelength longer than 330 nm. The results suggested that UV light between 330–370 nm could kill the cells. Additions of H2O2 solution with different concentrations to the cell cultures caused the changing deflection signal from a living cell either unchanged or changed in different trend, suggesting toxicity of H2O2 to the cells. The results from the beam deflection detection agreed well with those obtained by the conventional trypane blue method.Escherichia coli as a plasmid recipient cell was dispersed in a chrysotile colloidal solution, containing chrysotile adsorbed to plasmid DNA (chrysotile-plasmid cell mixture). Following this, the chrysotile-plasmid cell mixture was dropped onto the surface of an elastic body, such as agarose, and treated physically by sliding a polystyrene streak bar over the elastic body to create friction. Plasmid DNA was easily incorporated into E. coli, and antibiotic resistance was conferred by transformation. The transformation efficiency of E. coli cultured in solid medium was greater than that of E. coli cultured in broth. To obtain greater transformation efficiency, we attempted to determine optimal transformation conditions. The following conditions resulted in the greatest transformation efficiency: the recipient cell concentration within the chrysotile-plasmid cell mixture had an optical density greater than or equal to 2 at 550 nm, the vertical reaction force applied to the streak bar was greater than or equal to 40 g, and the rotation speed of the elastic body was greater than or equal to 34 rpm. Under these conditions, we observed a transformation efficiency of 107 per μg plasmid DNA. The advantage of achieving bacterial transformation using the elastic body exposure method is that competent cell preparation of the recipient cell is not required. In addition to E. coli, other Gram negative bacteria are able to acquire plasmid DNA using the elastic body exposure method.We have determined and quantified spectrophotometrically the capacity of producing reactive oxygen species (ROS) as 1O2 during the photolysis with UV-A light of 5 new synthesized naphthyl ester derivates of well-known quinolone antibacterials (nalidixic acid (1), cinoxacin (2), norfloxacin (3), ciprofloxacin (4) and enoxacin (5)). The ability of the naphthyl ester derivatives (6–10) to generate singlet oxygen were detecting and for the first time quantified by the histidine assay, a sensitive, fast and inexpensive method. The following tendency of generation of singlet oxygen was observed: compounds 7 > 10 > 6 > 8 > 9 >> parent drugs 1–5.High-performance liquid chromatography (HPLC) analysis was used for identification of two problematic ureides, asparagine and citrulline. We report here a technique that takes advantage of the predictable delay in retention time of the co-asparagine/citrulline peak to enable both qualitative and quantitative analysis of asparagine and citrulline using the Platinum EPS reverse-phase C18 column (Alltech Associates). Asparagine alone is eluted earlier than citrulline alone, but when both of them are present in biological samples they may co-elute. HPLC retention times for asparagine and citrulline were influenced by other ureides in the mixture. We found that at various asparagines and citrulline ratios [= 3:1, 1:1, and 1:3; corresponding to 75:25, 50:50, and 25:75 (μMol ml−1/μMol ml−1)], the resulting peak exhibited different retention times. Adjustment of ureide ratios as internal standards enables peak identification and quantification. Both chemicals were quantified in xylem sap samples of pecan [Carya illinoinensis (Wangenh.) K. Koch] trees. Analysis revealed that tree nickel nutrition status affects relative concentrations of Urea Cycle intermediates, asparagine and citrulline, present in sap. Consequently, we concluded that the HPLC methods are presented to enable qualitative and quantitative analysis of these metabolically important ureides.Microalbuminuria is associated with hypertension and is a strong risk factor for subsequent chronic disease, both renal and coronary heart disease (CHD), Presently there are several methods available for measurement of microalbuminuria. The aim of this study was to evaluate if the three different methods gave similar information or if one of the assays were superior to the others. Blood pressure, inflammatory markers and cardiovascular mortality and morbidity were correlated with urine albumin analysed with a point-of-care testing (POCT) instrument, nephelometric determination of albumin and albumin/creatinine ratio in elderly males. The study population consisted of 103 diabetic and 603 nondiabetic males (age 77 years) in a cross-sectional study. We analyzed urine albumin with a HemoCue® Urine Albumin POCT instrument and a ProSpec® nephelometer and albumin/creatinine ratio. There were strong correlations between both systolic and diastolic blood pressure and all three urine albumin methods (p < 0.0001). There were also significant correlations between the different urine albumin measurements and serum amyloid A component, high-sensitivity C-reactive protein and interleukin-6. The three different urine albumin methods studied provided similar information in relation to cardiovascular disease. There was a strong correlation between systolic and diastolic blood pressure and microalbuminuria in both the whole study population and in nondiabetic males emphasizing the role of hypertension in glomerular damage. The good correlation between the studied urine albumin measurements show that all three methods can be used for monitoring urine albumin excretion.Chromium is an important constituent widely used in different industrial processes for production of various synthetic materials. For evaluation of workers’ exposure to trace toxic metal of Cr (III), environmental and biological monitoring are essential processes, in which, preparation of samples is one of the most time-consuming and error-prone aspects prior to analysis. The use of solid-phase extraction (SPE) has grown and is a fertile technique of sample preparation as it provides better results than those produced by liquid-liquid extraction (LLE). SPE using mini columns filled with XAD-4 resin was optimized regarding to sample pH, ligand concentration, loading flow rate, elution solvent, sample volume, elution volume, amount of resins, and sample matrix interferences. Chromium was retained on solid sorbent and was eluted with 2 M HNO3 followed by simple determination of analytes by using flame atomic absorption spectrometery. Obtained recoveries of metal ion were more than 92%. The optimized procedure was also validated with three different pools of spiked urine samples and showed a good reproducibility over six consecutive days as well as six within-day experiments. Through this study, suitable results were obtained for relative standard deviation, therefore, it is concluded that, this optimized method can be considered to be successful in simplifying sample preparation for trace residue analysis of Cr in different matrices for evaluation of occupational and environmental exposures. To evaluate occupational exposure to chromium, 16 urine samples were taken, prepared, and analyzed based on optimized procedure.Mistletoe Extracts (ME) are of growing interest to pharmacological research because of their apoptosis-inducing/cytostatic and immunomodulatory effects. The standardization of the three different groups of Mistletoe Isolectins (ML-I, II and III) is often rendered more difficult since the primary structures are nearly identical. Their classification is based on their Galactose- and N-acetyl-D-galactosamine (GalNAc)-specificity which was measured by various inhibitory assays. The aim of the present study was to improve the characterization of the direct binding activity of the isolectins from ME to immobilized lactose, GalNAc and to the oligosaccharide asialofetuin. After careful ultrafiltration of fresh ME, affinity chromatography was carried out using lactose- agarose, GalNAc—agarose and asialofetuin—affigel 15 columns. MLs were further purified by Sephadex G-100 or by cation exchange chromatography which was adapted to a Fast Protein Liquid Chromatography (FPLC) system. Proteins from both fresh plants and commercial ME were able to bind immobilized lactose to a considerable extent. The majority of this lectin has a B-chain with a Molecular Weight (MW) of 34kD and an A-chain with a MW of 29 kD (ML-I). Only a minor part of the lactose-binding proteins has a lower MW, namely 32kD and 27kD (MLII). However, neither MLs which were eluted from lactose columns, nor the proteins from fresh plant or ME showed a direct binding to the immobilized GalNAc. In spite of this deficiency, GalNAc was able to induce a considerable (25% and 32%) inhibitory effect on their binding to immobilized asialofetuin indicating a discrepancy between the lectin binding and inhibiting effects of GalNAC. Consequently, for an improved standardization of ME more specific sugar molecules are necessary.Pentavalent technetium-99m dimercaptosuccinic acid (99mTc-(V)DMSA) is a tumor-seeking agent which was introduced to evaluate, image, and manage many types of cancers. In this review, the beginning of, and the most recent applications of using this agent was appraised. The relation with tumor cell detection and proliferation was reported and several mechanisms of uptake of 99mTc-(V)DMSA in tumor cells are described.We studied the near UV absorption spectrum of canine plasminogen. There are 19 tryptophans, 19 phenylalanines and 34 tyrosines in the protein. 4th derivative spectra optimized for either tryptophan or tyrosine give a measure of the polarity of the environments of these two aromatic amino acids. Plasminogen at temperatures between 0 °C and 37 °C exists as a mixture of four conformations: closed-relaxed, open-relaxed, closed-compact, and open-compact. The closed to open transition is driven by addition of ligand to a site on the protein. The relaxed to compact transition is driven by increasing temperature from 0 °C to above 15–20 °C. When the conformation of plasminogen is mainly closed-relaxed, the 4th derivative spectra suggest that the average tryptophan environment is similar to a solution of 20% methanol at the same temperature. Under the same conditions, 4th derivative spectra suggest that the average tyrosine environment is similar to water. These apparent polarities change as the plasminogen is forced to assume the other conformations. We try to rationalize the information based on the known portions of the plasminogen structure.Chirasil-β-Dex containing an undecamethylene spacer (C11-Chirasil-Dex) was synthesized and used as chiral stationary phase (CSP) in enantioselective gas chromatography (GC). The versatility of the new stationary phase in the simultaneous enantiomeric separation of a set of N-alkylated barbiturates is demonstrated.We have developed a two-dimensional (2D-) gel system of zymography and reverse zymography for the detection and characterization of proteases and protease inhibitors. Isoelectric focusing (IEF) agarose gels with pH gradients were employed for separation in the first-dimension and sodium dodecyl sulfate (SDS)-polyacrylamide gel copolymerized with gelatin used for the second dimension. Proteases and protease inhibitors separated by IEF gel were applied on the second gel without trichloroacetic acid (TCA) fixation. Protease activity in the 2D-gel was visualized as transparent spots where gelatin substrate was digested after commassie brilliant blue (CBB) staining. Some of the transparent spots from the skin mucus extract of rainbow trout were determined to be a cysteine protease through use of E-64 or CA-074. In the reverse zymography technique, the gel was incubated with papain solution at 37 degrees C for 18 h. Cysteine protease inhibitors from broad bean seeds were detected as clear blue spots after CBB staining. The amino (N-) terminal sequences of four papain inhibitor spots thus detected were demonstrated to be identical to that of favin beta chain, a broad bean lectin. Taken together, our system can be considered to be an efficient technique for discovering and characterizing new proteases and protease inhibitors in biological samples. This is the first report describing a 2D-gel system of zymography and reverse zymography.The present study introduces a method for determining the labile iron pool (LIP) in human lymphocytes. It is measured using the probe CP655, the fluorescence of which is stoichiometrically quenched by the addition of iron. The intracellular CP655 fluorescence in lymphocytes was quenched by increasing intracellular iron concentrations using the highly lipophilic 8-hydroxyquinoline iron complex. Intracellular fluorescence quenching, mediated by the physiological intracellular labile iron, can be recovered on the addition of excess membrane-permeable iron chelator, CP94. The intracellular probe concentration was measured using laser scanning microscopy. An ex situ calibration was performed in a “cytosolic” medium based on the determined intracellular CP655 concentration and probe fluorescence quenching in the presence of iron. The concentration of the LIP of healthy human lymphocytes was determined to be 0.57 ± 0.27 μM. The use of the fluorescent probe CP655 renders it possible to record the time course of iron uptake and iron chelation by CP94 in single intact lymphocytes.The aim of this study is to adopt the approach of metabolic fingerprinting through the use of Fourier Transform Infrared (FTIR) technique to understand changes in the chemical structure in Padina tetrastromatica (Hauck). The marine brown alga under study was grown in two different environmental conditions; in natural seawater (P. tetrastromatica (c)) and in seawater suplemented with 50 ppm of cadmium (P. tetrastromatica (t)) for a three-week period in the laboratory. The second derivative, IR specrum in the mid-infrared region (4000–400 cm−1) was used for discriminating and identifying various functional groups present in P. tetrastromatica (c). On exposure to Cd, P. tetrastromatica (t) accumulated 412 ppm of Cd and showed perturbation in the band structure in the mid-IR absorption region. Variation in spectral features of the IR bands of P. tetrastromatica (untreated and treated) suggests that cadmium ions bind to hydroxyl, amino, carbonyl and phosphoryl functionalities. This was attributable to the presence of the following specific bands. A band at 3666 cm−1 in untreated P. tetrastromatica (c) while a band at 3560 cm−1 in Cd-treated P. tetrastromatica (t) due to non bonded and bonded O-H respectively. Similarly, non bonded N-H for P. tetrastromatica (c) showed two bands at 3500 cm−1 and 3450 cm−1 due to the N-H stretching vibrations and a band at 1577 cm−1 due to N-H bending vibrations, while an intense band at 3350 cm−1 due to bonded N-H stretching vibrations and at 1571 cm−1 due to bending vibrations was observed for Cd-treated P. tetrastromatica (t). Involvement of ester carbonyl group is characterized by the presence of a band at 1764 cm−1 in untreated P. tetrastromatica (c) while the Cd-treated P. tetrastromatica (t) showed the band at 1760 cm−1. The intensity of the band at 1710 cm−1 in the control samples decreased drastically after cadmium treatment indicating carbonyl of COOH to be involved in metal chelation. A band at 1224 cm−1 for untreated P. tetrastromatica (c) and at 1220 cm−1 for Cd-treated P. tetrastromatica (t) is indicative of the involvement of phosphoryl group in metal binding. Several other such changes were also evident and discussed in this paper. Based on our observation, FTIR technique proves to be an efficient tool for detecting structural changes and probable binding sites induced by the presence of a metal pollutant, cadmium, in the marine environment.A high-performance liquid chromatographic (HPLC) method has been developed for the separation and determination of S- and R-enantiomers of betaxolol in tablets and ophthalmic preparations. Baseline resolution was achieved by using teicoplanin macrocyclic antibiotic chiral stationary phase (CSP) known as Chirobiotic T with fluorescence detection at excitation/emission wavelengths 275/305 nm. The polar ionic mobile phase (PIM) consists of methanol-glacial acetic acid-triethylamine, (100:0.020:0.025, v/v/v) has been used at a flow rate of 1.5 ml/min. All analytes with S-(–)-atenolol as internal standard were conducted at ambient temperature. The method is highly specific where another coformulated compounds did not interfere. The stability of betaxolol enantiomers under different degree of temperature also studied. The results showed that it is stable for at least 7 days at 70°C. The method validated for its linearity, accuracy, precision and robustness. Experimental design was used during validation to evaluate method robustness. Using the chromatographic conditions described, S- and R-betaxolol were well resolved with mean retention times of 11.3 and 12.6 min, respectively. Linear response (r > 0.997) was observed over the range of 10–500 ng/ml of betaxolol enantiomers, with detection limit of 5 ng/ml. The recoveries of S- and R-betaxolol from tablets and ophthalmic preparation ranged from 97.4 to 101.4% and 98.0 to 102.0%, respectively. The mean relative standard deviation (R.S.D.%) for both enantiomers were 1.1–1.4% and 1.3–1.7% in tablets and ophthalmic solution, respectively.Protein kinases catalyze the transfer of the γ-phosphoryl group of adenosine triphosphate (ATP) to the hydroxyl groups of protein side chains, and they play critical roles in regulating cellular signal transduction and other biochemical processes. They are attractive targets for today’s drug discovery and development, and many pharmaceutical companies are intensively developing various kinds of protein kinase inhibitors. A good example is the recent success with the Bcr-Abl tyrosine kinase inhibitor imatinib mesylate (Gleevec™) in the treatment of chronic myeloid leukemia. Though imatinib has dramatically improved the treatment of Bcr-Abl-positive chronic myeloid leukemia, resistance is often found in patients with advanced-stage disease. Several mechanisms have been proposed to explain this resistance, including point mutations within the Abl kinase domain, amplification of the bcr-abl gene, overexpression of the corresponding mRNA, increased drug efflux mediated by P-glycoprotein, and activation of the Src-family kinase (SFK) Lyn. We set out to develop a novel drug whose affinity for Abl is higher than that of imatinib and whose specificity in inhibiting Lyn is higher than that of SFK/Abl inhibitors such as dasatinib (Sprycel™) or bosutinib (SKI-606). Our work has led to the development of NS-187 (INNO-406), a novel Abl/Lyn dual tyrosine kinase inhibitor with clinical prospects. To provide an overview of how a selective kinase inhibitor has been developed, this review presents chemical-modification studies carried out with the guidance of molecular modeling, the structural basis for the high potency and selectivity of NS-187 based on the X-ray structure of the NS-187/Abl complex, and the biological profiling of NS-187, including site-directed mutagenesis experiments.

Analytical Study for the Charge-Transfer Complexes of Rosuvastatin Calcium with π-Acceptors

Studies were carried out to investigate the charge-transfer (CT) reaction of ROS-Ca, as a n-electron donor with various π-acceptors: tetracyanoethylene, p-chloranilic acid, 2,3-dichloro-5,6-dicyano-1,4-benzoquinone, 2,3,5,6-tetrabromo-1,4-benzoquinone, 1,3,5-trinitrobenzene, 2,3,5,6-tetrachloro-1,4-benzoquinone, 7,7,8,8-tetracyano-quinodimethane, and 2,4,7-trinitro-9-fluorenone. Different colored CT complexes were obtained. The reaction mechanism and site of interaction were determined by ultraviolet-visible spectrophotometric techniques and computational molecular modeling. The formation of the colored complexes was utilized in the development of simple, rapid and accurate spectrophotometric methods for the determination of ROS-Ca. Under the optimum reaction conditions, linear relationships with good correlation coefficients (0.9984–0.9995) were found between the absorbances and the concentrations of ROS-Ca in the range of 2–200 μg mL−1. The limits of detection ranged from 0.41 to 12.24 μg mL−1. No interference could be observed from the additives commonly present in the tablets or from the drugs that are co-formulated with ROS-Ca in its combined formulations. The methods were successfully applied to the analysis of tablets with good accuracy and precision; the recovery percentages ranged from 99.54–100.46 ± 1.58–1.82%. The results were compared favorably with the reported method. The proposed methods are practical and valuable for routine application in quality control laboratories for determination of ROS-Ca in its bulk form and tablets.

Development of an HPLC method for the quantitation of bisoprolol enantiomers in pharmaceutical products using a teicoplanin chiral stationary phase and fluorescence detection

Abstract A selective high performance liquid chromatographic (HPLC) method was developed for the separation and quantification of bisoprolol enantiomers in pharmaceutical products. The method is highly specific where another co-formulated drug, hydrochlorothiazide, did not interfere. Baseline resolution was achieved by using teicoplanin macrocyclic antibiotic chiral stationary phase (CSP), known as Chirobiotic T, with fluorescence detection at excitation/emission wavelengths 275/305 nm. The polar ionic mobile phase (PIM) consisting of methanol‐glacial acetic acid‐triethylamine, (100:0.020:0.025), (v/v/v) has been used at a flow rate of 1.5 mL/min. All analytes with S‐(−)‐atenolol as the internal standard were conducted at room temperature. The stability of bisoprolol enantiomers under different degrees of temperature was also studied. The results showed that the drug is stable for at least 7 days at 70°C. The method was validated for its linearity, accuracy, precision, and robustness. An experimental design was used during validation to evaluate method robustness. The calibration curves were linear over the range of 5‐250 ng/mL for each enantiomer, with a correlation coefficient of 0.999 for both enantiomers. The overall recoveries of S‐(−)‐ and R‐(+)‐bisoprolol from pharmaceutical products ranged from 97.6 to 100.5% with %RSD ranging from 0.7 to 2.6%. The limit of quantification (LOQ) and limit of detection (LOD) for each enantiomer were 5 and 2 ng/mL, respectively. The method proved to be of chiral quality control for bisoprolol formulations by HPLC.

Determination of Luteolin and Apigenin in Herbs by Capillary Electrophoresis with Diode Array Detection

Capillary electrophoresis with a diode array detector was employed for the determination of luteolin and apigenin in plant extracts. The experimental factors affecting the elution of the analytes were carefully optimized. The final analysis was achieved utilizing a fused silica capillary (58 cm effective length, 75 μm ID) and a background electrolyte solution consisting of borax buffer (20 mM, pH 10.0) and methanol (90: 10, v/v) with a 23 kV driving voltage and detection at 210 nm. The method was fully validated as per the guidelines of the International Conference on Harmonization for Analytical Procedures. The relationship between peak area and concentration was linear between 3 and 800 μg/mL for both compounds with detection limits of 1.05 for luteolin and 0.53 μg/mL for apigenin. The method was employed for the determination of the analytes in extracts of thyme and parsley. Both compounds were resolved from interfering peaks that were present in the extracts. Recovery studies were performed by fortifying the extracts with standards and demonstrated good accuracy with recovery values between 97.29 and 104.88% for luteolin and 96.89 and 105.18% for apigenin. Thyme and parsley were shown to contain high concentrations of luteolin and apigenin.

Novel Stereoselective High-Performance Liquid Chromatographic Method for Simultaneous Determination of Guaifenesin and Ketorolac Enantiomers in Human Plasma

A novel method was developed for the simultaneous determination of guaifenesin (GUA) and ketorolac tromethamine (KET) enantiomers in plasma samples. Since GUA probably increases the absorption of coadministered drugs (e.g., KET), it would be extremely important to monitor KET plasma levels for the purpose of dose adjustment with a subsequent decrease in the side effects. Enantiomeric resolution was achieved on a polysaccharide-based chiral stationary phase, amylose-2, as a chiral selector under the normal phase (NP) mode and using ornidazole (ORN) as internal standard. This innovative method has the advantage of the ease and reliability of sample preparation for plasma samples. Sample clean-up was based on simply using methanol for protein precipitation followed by direct extraction of drug residues using ethanol. Both GUA and KET enantiomers were separated using an isocratic mobile phase composed of hexane/isopropanol/trifluoroacetic acid, 85:15:0.05 v/v/v. Peak area ratios were linear over the range 0.05-20 µg/mL for the four enantiomers S (+) GUA, R (-) GUA, R (+) KET, and S (-) KET. The method was fully validated according to the International Conference on Harmonization (ICH) guidelines in terms of system suitability, specificity, accuracy, precision, robustness, and solution stability. Finally, this procedure was innovative to apply the rationale of developing a chiral high-performance liquid chromatography (HPLC) procedure for the simultaneous quantitative analysis of drug isomers in clinical samples.

Simultaneous determination of dexamethasone and lenalidomide in rat plasma by solid phase extraction and ultra-performance liquid chromatography-tandem mass spectrometry: application to pharmacokinetic studies

An ultra-performance liquid chromatography method with tandem mass spectrometric detection (UPLC-MS/MS) has been developed and validated for the simultaneous determination of lenalidomide (LND) and dexamethasone (DEX) in rat plasma using domperidone (DOM) as an internal standard (IS). Sample preparation was performed using solid phase extraction methodology (SPE) followed by chromatographic analysis on a C 18 column (100 × 1.0 mm, i.d., 1.7 μm particle size) and a mobile phase composed of (0.1% formic acid in water) and (0.1% formic acid in acetonitrile) in the ratio of (20 : 80, v/v) at the flow rate of 0.2 mL min−1. Electrospray ionization (EI) in the positive ionization mode using multiple reaction monitoring (MRM) was applied to detect the transitions of DEX at m/z 393 > 147, LND at m/z 260 > 149 (LND), and DOM at m/z 426 > 175. The method was validated over the concentration range of 0.01–5 ng mL−1 with a very low limit of quantitation of 0.01 ng mL−1 for both LND and DEX. Recoveries of both analytes from plasma samples ranged from 86–106% throughout their linear ranges. Intra-day and inter-day precision was evaluated and in all cases, the RSD values were within the acceptance values (<15%). The applicability of the method was extended to the determination of the pharmacokinetics of both LND and DEX, following their oral administration to rats, either alone or in combination, suggesting the applicability of the method in further clinical studies.

Novel spectrophotometric method for determination of cinacalcet hydrochloride in its tablets via derivatization with 1,2-naphthoquinone-4-sulphonate

This study represents the first report on the development of a novel spectrophotometric method for determination of cinacalcet hydrochloride (CIN) in its tablet dosage forms. Studies were carried out to investigate the reaction between CIN and 1,2-naphthoquinone-4-sulphonate (NQS) reagent. In alkaline medium (pH 8.5), an orange red-colored product exhibiting maximum absorption peak (λmax) at 490 nm was produced. The stoichiometry and kinetic of the reaction were investigated and the reaction mechanism was postulated. This color-developing reaction was employed in the development of a simple and rapid visible-spectrophotometric method for determination of CIN in its tablets. Under the optimized reaction conditions, Beers law correlating the absorbance with CIN concentration was obeyed in the range of 3 - 100 μg/ml with good correlation coefficient (0.9993). The molar absorptivity (ε) was 4.2 × 105 l/mol/cm. The limits of detection and quantification were 1.9 and 5.7 μg/ml, respectively. The precision of the method was satisfactory; the values of relative standard deviations (RSD) did not exceed 2%. No interference was observed from the excipients that are present in the tablets. The proposed method was applied successfully for the determination of CIN in its pharmaceutical tablets with good accuracy and precisions; the label claim percentage was 100.80 - 102.23 ± 1.27 - 1.62%. The results were compared favorably with those of a reference pre-validated method. The method is practical and valuable in terms of its routine application in quality control laboratories.