Haya I. Aljohar

Development of Capillary Electrophoresis Technique for Simultaneous Measurement of Amlodipine and Atorvastatin from Their Combination Drug Formulations

Abstract A simple, accurate, precise, and sensitive capillary electrophoresis (CE) technique coupled to a diode array detector (DAD) has been developed for the separation and simultaneous determination of amlodipine (AM) and atorvastatin (AT) from their combination formulations. The proposed method utilized fused silica capillary (50 cm × 75 µm ID) and background electrolyte (BGE) composed of phosphate buffer (pH 6.5, 25 mM)-methanol, (80:20, v/v). The separation was achieved at 15 KV applied voltage and 25°C. Losartan was chosen as the internal standard to guarantee a high level of quantitative performance. The two drugs were subjected to thermal, photolytic, hydrolytic, and oxidative stress conditions and the stressed samples were analyzed by the proposed method. The method has shown adequate separation for AM and AT from its main degradation products (UK-55-410) & (PD 0162910-00), respectively, which demonstrated the specificity of the assay. The described method was linear over the range of 1 – 50 µg/mL (r = 0.9998) for both drugs (2.4 × 10−6 − 1.2 × 10−4 M for AM and 1.8 × 10−6 −8.6 × 10−5 M for AT). Intra- and inter-day RSD (n = 6) was ≤2.2%. The limits of detection for AM and AT were 0.5 µg/mL. The percentage recoveries (n = 6) of the two drugs from their tablet formulations were 99.97 ± 1.84 and 100.96 ± 1.12, respectively. Degradation products produced as a result of stress studies did not interfere with the detection of AM and AT and the assay can thus be considered stability indicating.

Multi-objective optimization strategy based on desirability functions used for electrophoratic separation and quantification of rosiglitazone and glimepiride in plasma and formulations

Multiple response simultaneous optimization employing Derringers desirability function was used for the development of a capillary electrophoresis method for the simultaneous determination of rosiglitazone (RSG) and glimepiride (GLM) in plasma and formulations. Twenty experiments, taking the two resolutions, the analysis time, and the capillary current as the responses with three important factors--buffer morality, volte and column temperature--were used to design mathematical models. The experimental responses were fitted into a second order polynomial and the six responses were simultaneously optimized to predict the optimum conditions for the effective separation of the studied compounds. The separation was carried out by using capillary zone electrophoresis (CZE) with a silica capillary column and diode array detector at 210 nm. The optimum assay conditions were 52 mmol l⁻¹ phosphate buffer, pH 7, and voltage of 22 kV at 29 °C. The method showed good agreement between the experimental data and predictive value throughout the studied parameter space. The assay limit of detection was 0.02 µg ml⁻¹ and the effective working range at relative standard deviation (RSD) of ≤ 5% was 0.05-16 µg ml⁻¹ (r = 0.999) for both drugs. Analytical recoveries of the studied drugs from spiked plasma were 97.2-101.9 ± 0.31-3.0%. The precision of the assay was satisfactory; RSD was 1.07 and 1.14 for intra- and inter-assay precision, respectively. The proposed method has a great value in routine analysis of RSG and GLM for its therapeutic monitoring and pharmacokinetic studies.

4-[(4-Acetylphenyl)amino]-2-methylidene-4-oxobutanoic acid, a newly synthesized amide with hydrophilic and hydrophobic segments: Spectroscopic characterization and investigation of reactive properties

The FT-IR and FT-Raman spectra of 4-[(4-acetylphenyl)amino]-2-methylidene-4-oxobutanoic acid were recorded. The vibrational wavenumbers were computed DFT quantum chemical calculations and the vibrational assignments were done using potential energy distribution. The theoretically predicted geometrical parameters were in agreement with the XRD data. Determination and visualization of molecule sites prone to electrophilic attacks has been performed by mapping of average local ionization energies (ALIE) to electron density surface. Further determination of possible reactive centres of title molecule has been done by calculation of Fukui functions. Intramolecular noncovalent interactions have also been determined and visualized. Prediction of molecule sites possibly prone to the autoxidation has also been done by calculations of bond dissociation energies (BDE), while the stability of the title molecule in water was assessed by calculation of radial distribution functions (RDF) obtained after molecular dynamics (MD) simulations. The docked ligand title compound forms a stable complex with IRK and gives a binding affinity of -10.2 kcal/mol.

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.

Artificial neural network modeling of the electrophoretic mobility of dexamethasone and two additives in micellar electrokinetic capillary chromatography

Multiple response simultaneous optimization was used to develop a micellar electrokinetic capillary chromatography (MEKC) method for the determination of dexamethasone sodium phosphate (DEX) and the two additives, creatinine (CRE) and propylparaben (PRO) in DEX ampoules. The goal is to optimize the separation parameters to achieve maximum resolution between the three components within a reasonable run time. Buffer composition and voltage were optimized using an artificial neural network (ANN). The best neural network with a “2-10-4” structure and 150 epochs was applied. A back propagation algorithm with sigmoidal transformation function in the nodes was used for constructing the ANN. The generalization ability was studied by consulting the network with test data and calculating the performance parameters, e.g. correlation (R), mean square error (MSE), root mean square error (RMSE) and the percentage-relative error (Er%). The predicted results were in good agreement with the experimental values, indicating that a neural network is a potential method for the selection of separation conditions in MEKC. The optimum separation was achieved when using a background electrolyte of 20 mM borate buffer containing 30 mM sodium dodecyl sulfate (SDS) at pH 9.5 along with applying high voltage (30 kV) to the capillary. The total separation was reached within 4.39 min. This optimized method was applied for the analysis of commercial DEX ampoules. The method was fully validated as per ICH guidelines.

Microemulsion electrokinetic chromatography with polarity switching stacking mode for the determination of dexamethasone and dexamethasone sodium phosphate: application to pharmacokinetic studies in rabbit plasma

A novel method based on microemulsion electrokinetic chromatography (MEEKC) with reversed electrode polarity stacking mode (REPSM) was developed and validated for the simultaneous determination of dexamethasone sodium phosphate (DEX-SP) and the active drug dexamethasone (DEX) in rabbit plasma. The optimum separation was achieved when a microemulsion background electrolyte consisting of 30 mM borate buffer (pH 9.2), 20 mM sodium dodecyl sulfate (SDS), 0.8% ethyl acetate and 2% 1-butanol was used. Electrophoretic separation was carried out at 24 °C and at +23 kV. A stacking technique has been developed to pre-concentrate samples and to increase the amount of sample that can be loaded onto the capillary without degrading the separation, up to 160 s. REPSM was applied using the following optimized program: +23 kV (0–0.6 min) then −23 kV (0.6–1.5 min) and finally +23 kV for the rest of the run. The analytes were base-line resolved within 12 min. Using hydrochlorothiazide (HCT) as the internal standard, the peak area ratios were found to be linear in the concentration range of 0.1–2.0 μg mL−1 for DEX-SP and 0.05–2.0 μg mL−1 for DEX. The applied stacking mode increased the detectability of the method by about 40-fold with limits of detection and quantitation of 0.03 and 0.1 μg mL−1 for DEX-SP, and 0.02 and 0.05 μg mL−1 for DEX, respectively. The developed method was fully validated according to the ICH guidelines. This optimized method was applied for the determination of DEX-SP and DEX in rabbit plasma samples previously treated with I.V. injection of DEX-SP. The in vivo results thus obtained were used to study the pharmacokinetics of the cited drugs in rabbit plasma.

Physical and chemical screening of honey samples available in the Saudi market: An important aspect in the authentication process and quality assessment

Honey is becoming accepted as a reputable and effective therapeutic agent by practitioners of conventional medicine and by the general public. It has many biological activities and has been effectively used in the treatment of many diseases, e.g. gastrointestinal diseases, skin diseases, cancer, heart diseases, and neurological degeneration. Honey is an excellent source of energy containing mainly carbohydrates and water, as well as, small amounts of organic acids, vitamins, minerals, flavonoids, and enzymes. As a natural product with a relatively high price, honey has been for a long time a target for adulteration. The authenticity of honey is of great importance from commercial and health aspects. The study of the physical and chemical properties of honey has been increasingly applied as a certification process for the purpose of qualification of honey samples. The current work focusses on studying the authenticity of various types of honey sold in Riyadh market (24 samples). For this purpose, physical properties (pH, hydroxylmethylfurfural HMF, and pollen test) were measured. Besides, sugar composition was evaluated using Fehling test and an HPLC method. Elemental analysis was carried out using inductively coupled plasma (ICP). In addition, the presence of drug additives was assessed by means of GC–MS. The obtained results were compared with the Saudi Arabian standards, Codex Alimentarius Commission (2001), and harmonized methods of the international honey commission.

Crystal structure of N′-[(1E)-(2,6-dichlorophenyl)-methylidene]adamantane-1-carbohydrazide, C18H20Cl2N2O

Abstract C18H20Cl2N2O, orthorhombic, Pbca (No. 61), a = 8.1023(2) Å, b = 18.7063(4) Å, c = 22.5509(6) Å, V = 3417.91(14) Å3, Z = 8, Rgt(F) = 0.0496, wRref(F2) = 0.1535, T = 293(2).

Determination of methyl gallate in Bauhinia retusa extract by high-performance liquid and thin-layer chromatography

ABSTRACT Two stability-indicating chromatographic methods are reported for the determination of methyl gallate in crude extracts of Bauhinia retusa. Separation by high performance thin layer chromatography was conducted on silica gel aluminum sheets using 9.5:0.5:0.2 (v/v/v) chloroform:methanol:acetic acid at 280 nm. The results from the 2–40 µg/band were used to prepare a linear calibration graph. The limits of detection and quantitation were 0.5 and 1.5 µg/band, respectively. The reverse phase high performance liquid chromatographic isolation of methyl gallate was performed at ambient temperature with an injection volume of 10 μL. The mobile phase consisted of 40:60 (v/v) methanol:0.1% ortho-phosphoric acid. The separation was performed at 1 mL/min using a detection wavelength of 280 nm. The calibration graph for methyl gallate was rectilinear from 0.02–40 µg/mL with limits of detection and quantitation of 0.004 and 0.010 µg/mL, respectively. For both methods, intra-day and inter-day precision were evaluated and the relative standard deviation was less than 2%, indicating good precision. The robustness was evaluated by making small and deliberate changes to appropriate parameters and the calculated relative standard deviation was less than 2%.The chromatographic methods were employed to determine methyl gallate in crude Bauhinia retusa extracts.