A new spectrofluorimetric assay method for vandetanib in tablets, plasma and urine

Purpose: To develop a simple and sensitive spectrofluorimetric method for the determination of vandetanib (VDB) in tablets (containing 100 mg of the drug) and biological fluids (spiked human plasma and urine).Methods: The proposed method is based on examining the intrinsic fluorescence intensity of VDB in acetonitrile at 480 nm after excitation at 330 nm. Factors affecting fluorescence intensity of the cited drug (VDB), including the influence of pH, diluting solvent and time, were studied and optimized by one factor at a time approach. A calibration curve was constructed by plotting VDB fluorescence intensity at 480 nm versus VDB concentrations in ng mL-1. The method was validated according to the recommendations of International Conference on Harmonisation (ICH) for validation of the analytical proceduresResults: The linearity range of the method was 20 – 600 ng mL-1, with limits of quantification (LOQ) and of detection (LOD) of 30.45 and 10.05 ng mL-1, respectively. The adopted method was applied successfully to the quantitation of VDB in pure powder form (100.90 ± 0.91 %), laboratory prepared tablets (97.86 ± 1.42 %), spiked human plasma (97.97 ± 2.36 %) and urine (97.59 ± 0.87 %). Comparison of the proposed method with that of liquid chromatography-tandem mass spectrometry showed that there was no significant difference (p < 0.05) between the two methods in terms of accuracy and precision.Conclusion: The proposed method is simple and highly sensitive and, consequently, can be applied to assay VDB in biological samples as well as in dosage form.Keywords: Vandetanib, Spectrofluorimetry, Assay, Validation, Human plasma, Human urine, Dosage form

A novel method to determine new potent angiotensin inhibitor, azilsartan, in human plasma via micelle-enhanced spectrofluorimetry using cremophor RH 40

Purpose: To develop a micelle-enhanced spectrofluorimetric method for the assay of azilsartan (AZL) in bulk form and spiked human plasma without the need for derivatization procedure.Method: The proposed method was based on studying the fluorescence behavior of AZL in Cremophor RH 40 (Cr RH 40) micellar system. The fluorescence intensity was measured at 371 nm after excitation at 264 nm. The proposed procedure was validated according to International Council on Harmonization (ICH) guidelines.Results: In aqueous solution, the fluorescence intensity of AZL was greatly enhanced by more than 3- fold in the presence of Cr RH 40. The fluorescence –concentration plot was linear over the range of 10 – 500 ng.mL-1, with a limit of detection of 3.287 ngmL-1. The proposed method was successfully applied to the determination of AZL in pure powder form and spiked human plasma. The mean recovery of AZL in spiked human plasma using the proposed method was 90.54 ± 1.17 %.Conclusion: The suggested method is highly sensitive and simple, and can easily be applied for the quantification of AZL in pure powder form as well as in biological fluids such as plasmaKeywords: Azilsartan, Spectrofluorimetry, Spiked human plasma, Micellar syste

Simultaneous quantitative analysis of olmesartan, amlodipine and hydrochlorothiazide in their combined dosage form utilizing classical and alternating least squares based chemometric methods

Simultaneous spectrophotometric analysis of a multi-component dosage form of olmesartan, amlodipine and hydrochlorothiazide used for the treatment of hypertension has been carried out using various chemometric methods. Multivariate calibration methods include classical least squares (CLS) executed by net analyte processing (NAP-CLS), orthogonal signal correction (OSC-CLS) and direct orthogonal signal correction (DOSC-CLS) in addition to multivariate curve resolution-alternating least squares (MCR-ALS). Results demonstrated the efficiency of the proposed methods as quantitative tools of analysis as well as their qualitative capability. The three analytes were determined precisely using the aforementioned methods in an external data set and in a dosage form after optimization of experimental conditions. Finally, the efficiency of the models was validated via comparison with the partial least squares (PLS) method in terms of accuracy and precision

Enhanced spectrofluorimetric determination of the multitargeted tyrosine kinase inhibitor, crizotinib, in human plasma via micelle-mediated approach

Purpose: To quantify the multi-targeted tyrosine kinase inhibitor, crizotinib, in human plasma and bulk powder by highly sensitive micellar enhanced spectrofluorimetric procedure.Method: The developed procedure was based on measuring the fluorescence intensity of crizotinib (CRZ) in sodium dodecyl sulphate (SDS) micellar system at 404 nm after excitation at 271 nm. Validation of the developed procedure was carried out following ICH (International Council for Harmonization) guidelines.Results: Maximum fluorescence intensity (FI) was attained by addition of 0.2 mL SDS and 0.2 mL HCl (1N) to CRZ aliquots and then dilution with distilled water. There was a linear relationship between the FI of CRZ and its concentration over the range, 5 – 400 ng/mL, with limit of detection and of quantification of 1.857 and 5.628 ng/mL respectively. The developed procedure was successfully applied to assay CRZ in pure powder form and spiked human plasma with mean recovery of 100.68 ± 0.37 and 99.98 ± 0.20 %, respectively.Conclusion: The developed procedure is simple and sensitive, and can be applied to routine analysis of CRZ in pure powder form as well as in clinical laboratories for the determination of CRZ in plasma.Keywords: Crizotinib, Spectrofluorimetry, Micelle, Human plasma, Sodium dodecyl sulphat

Liquid chromatographic-tandem mass spectrometric assay for simultaneous quantitation of tofacitinib, cabozantinib and afatinib in human plasma and urine

Purpose: To develop a simple, adequately sensitive, and practical liquid chromatographic-mass spectrometric method to simultaneously quantify three tyrosine kinase inhibitors, viz, tofacitinib (TOF), cabozantinib (CBZ) and afatinib (AFB) after their extraction from both human plasma and urine.Methods: Blood and urine samples were obtained from healthy volunteers who admitted to not being on any medications. The investigated analytes were chromatographically separated on a C18 column (Luna®-PFP 100Å column, 50 mm × 2.0 mm i.d., 3.0 μm) with the aid of a mobile phase containing A; acetonitrile (ACN) and B; 0.01 M ammonium formate buffer (pH 4.1) pumped at a rate of 0.3 mL.min-1 in the ratio A:B, 50:50 v/v. Analyte monitoring was achieved by tandem mass spectrometry interfaced with an electrospray ionization source with the aid of multiple reaction monitoring (MRM) mode for analytes quantification.Results: The proposed method permitted a specific and sensitive determination of the investigated TKIs in the linear range of 1.0 - 100 ng mL-1 with correlation coefficient (r2) of 0.9991, 0.9997, and 0.9998 for TOF, CBZ and AFB, respectively. The method was validated with regard to its limits of quantification (ranging from 0.91 to 1.24 ng mL-1 for the 3 analytes), intra- and inter assay accuracy (in the range -1.85 to 1.22 %) and precision (0.71 - 5.12 %). The method was also validated in terms of recovery from both studied matrices, robustness and matrix effect.Conclusion: The results obtained reveal that the developed method is simple, specific and highly efficient for routine determination of the studied analytes in human plasma and urine. It can be reliably applied for high throughput analysis of clinical samples containing the investigated analytes.Keywords: Tyrosine kinase inhibitors, Tofacitinib, Cabozantinib, Afatinib, LC-MS/MS, human plasm

A spectroscopic, thermodynamic and molecular docking study of the binding mechanism of dapoxetine with calf thymus DNA

Dapoxetine is a selective serotonin reuptake inhibitor, used to treat premature ejaculation in men. Dapoxetine may interact with theDNAand hence this study investigated dapoxetine and calf thymusDNA(ctDNA) binding interaction. The interaction study of ligands to DNA is of importance in the development of molecular probes and therapeutic agents. Spectroscopic techniques including spectrofluorometry and spectrophotometry were employed to study this interaction. Fluorescence studies indicated a static quenching mechanism between dapoxetine and ctDNA. Groove binding was suggested as the mode of interaction between dapoxetine and ctDNA based onUVabsorption, circular dichroism (CD) spectroscopy, iodide quenching and molecular docking studies. The studies conducted at three different temperatures 298, 303 and 310 K indicated a strong binding interaction at higher temperatures. Thermodynamic studies conducted indicated involvement of hydrophobic interaction between ctDNA and dapoxetine and were entropy-driven. Ethidium bromide probe study suggested that dapoxetine does not bind to ctDNA in an intercalative fashion. Iodide quenching studies further proved the non-intercalative binding of ctDNA with dapoxetine. Ionic strength studies conducted ruled out the electrostatic binding mechanism between ctDNA and dapoxetine. Molecular docking analysis performed for the dapoxetine with calf thymus DNA (ctDNA) interaction and confirmed minor groove binding of dapoxetine to ctDNA. The study helped to reveal the binding interaction mechanism between dapoxetine and ctDNA

DNA binding Test, x-ray crystal structure, spectral studies, TG-DTA, and electrochemistry of [CoX2 (dmdphphen)] (dmdphphen is 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline,x = Cl, and NCS) complexes

Two new neutral mixed-ligand cobalt(II) complexes, CoCl2(dmdphphen) 1 and Co(NCS)dmdphphen) 2, where dmdphphen is 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline, were synthesized and characterized by an elemental analysis, UV-Vis, IR, TG/DTA, cyclic voltammetry CV, and single X-ray diffraction. Complex 2 crystallized as monoclinic with a space group P21/c. Co(II) ions are located in a distorted tetrahedral environment. TG/DTA result shows that these complexes are very stable and decomposed through one-step reaction. The two complexes exhibit a quasireversible one-electron response at -550 and 580 mV versus Cp2Fe/Cp2Fe+, which has been assigned to Co(I)/Co(II) and Co(II)/Co(III) couples. Absorption spectral studies reveal that such complexes exhibit hypochromicity during their interaction with CT-DNA. © 2014 Mousa Al-Noaimi et al

Genetic architecture of common bunt resistance in winter wheat using genome-wide association study

Background: Common bunt (caused by Tilletia caries and T. foetida) has been considered as a major disease in wheat (Triticum aestivum) following rust (Puccinia spp.) in the Near East and is economically important in the Great Plains, USA. Despite the fact that it can be easily controlled using seed treatment with fungicides, fungicides often cannot or may not be used in organic and low-input fields. Planting common bunt resistant genotypes is an alternative. Results: To identify resistance genes for Nebraska common bunt race, the global set of differential lines were inoculated. Nine differential lines carrying nine different genes had 0% infected heads and seemed to be resistant to Nebraska race. To understand the genetic basis of the resistance in Nebraska winter wheat, a set of 330 genotypes were inoculated and evaluated under field conditions in two locations. Out of the 330 genotypes, 62 genotypes had different degrees of resistance. Moreover, plant height, chlorophyll content and days to heading were scored in both locations. Using genome-wide association study, 123 SNPs located on fourteen chromosomes were identified to be associated with the resistance. Different degrees of linkage disequilibrium was found among the significant SNPs and they explained 1.00 to 9.00% of the phenotypic variance, indicating the presence of many minor QTLs controlling the resistance. Conclusion: Based on the chromosomal location of some of the known genes, some SNPs may be associated with Bt1, Bt6, Bt11 and Bt12 resistance loci. The remaining significant SNPs may be novel alleles that were not reported previously. Common bunt resistance seems to be an independent trait as no correlation was found between a number of infected heads and chlorophyll content, days to heading or plant height

Study of Interactions of an Anticancer Drug Neratinib With Bovine Serum Albumin: Spectroscopic and Molecular Docking Approach

Binding of therapeutic agents to plasma proteins, particularly to serum albumin, provides valuable information in the drug development. This study was designed to evaluate the binding interaction of neratinib with bovine serum albumin (BSA). Neratinib blocks HER2 signaling and is effective in trastuzumab-resistant breast cancer treatment. Spectrofluorometric, UV spectrophotometric, and fourier transform infrared (FT-IR) and molecular docking experiments were performed to study this interaction. The fluorescence of BSA is attributed to the presence of tryptophan (Trp) residues. The fluorescence of BSA in presence of neratinib was studied using the excitation wavelength of 280 nm and the emission was measured at 300-500 nm at three different temperatures. Neratinib quenched the BSA intrinsic fluorescence by static mechanism. A complex formation occurred due to the interaction leading to BSA absorption shift. The fluorescence, UV- absorption, three dimensional fluorescence and FT-IR data showed conformational changes occurred in BSA after interaction with neratinib. The binding constant values decreased as the temperature increased suggesting an instable complex formation at high temperature. Site I (sub-domain IIA) was observed as the principal binding site for neratinib. Hydrogen bonding and Van der Waals forces were suggested to be involved in the BSA-neratinib interaction due to the negative values of entropy and enthalpy changes