Development of a capillary electrophoresis method for the enantioselective estimation of primaquine in pharmaceutical formulations

A capillary electrophoresis (CE) method has been developed that allows the separation and estimation of primaquine enantiomers using hydroxypropyl-gamma-cyclodextrin (HP-gamma -CD) as a chiral selector. The influence of chemical and instrumental parameters on the separation, such as type and concentration of CD, buffer concentration, buffer pH, applied voltage, capillary temperature, and injection time, were investigated. Good separation of the racemic mixture of primaquine was achieved using a fused-silica capillary (52.5 cm effective length x 50 microm id) and a background electrolyte composed of tris-phosphate buffer solution (50 mM, pH 2.5) containing 15 mM HP-gamma-CD as a chiral selector. The recommended applied voltage, capillary temperature, and injection time were 15 kV, 25 degrees C, and 6 s, respectively. Within-day and interday reproducibility of peak area and migration time gave relative standard deviation values ranging from 1.05-3.30%. Good recoveries (range of 96.8-104.9%) were obtained from the determination of placebos that were spiked with 0.25-1.00 mg/L primaquine. The proposed CE method was successfully applied to the assay of primaquine diphosphate in pharmaceutical formulations (tablets).     

In vitro anticancer activity and biologically relevant metabolization of organometallic ruthenium complexes with carbohydrate-based ligands

The synthesis and in vitro anticancer activity of dihalogenido(eta6-p-cymene)(3,5,6-bicyclophosphite-alpha-D-glucofuranoside)ruthenium(II) complexes are described. The compounds were characterized by NMR spectroscopy and ESI mass spectrometry, and the molecular structures of dichlorido-, dibromido- and diiodido(eta6-p-cymene)(3,5,6-bicyclophosphite-1,2-O-isopropylidene-alpha-D-glucofuranoside)ruthenium(II) were determined by X-ray diffraction analysis. The complexes were shown to undergo aquation of the first halido ligand in aqueous solution, followed by hydrolysis of a P--O bond of the phosphite ligand, and finally formation of dinuclear species. The hydrolysis mechanism was confirmed by DFT calculations. The aquation of the complexes was markedly suppressed in 100 mM NaCl solution, and notably only very slow hydrolysis of the P--O bond was observed. The complexes showed affinity towards albumin and transferrin and monoadduct formation with 9-ethylguanine. In vitro studies revealed that the 3,5,6-bicyclophosphite-1,2-O-cyclohexylidene-alpha-D-glucofuranoside complex is the most cytotoxic compound in human cancer cell lines (IC50 values from 30 to 300 microM depending on the cell line).     

Uptake of Tm(III) ions onto polyurethane foam from H2O - ethanol mixture containing 1-(2-pyridylazo)-2-naphthol (PAN)

Summary The sorption of microquantities of Tm(III) ions on washed polyurethane foam (PUF) from a mixture of aqueous solution and ethanol containing PAN was examined. The maximum sorption of 3.18^. 10^-6M solution of Tm(III) ions was observed at pH 8 with 30-minute equilibration time. The optimum ratio of aqueous-ethanol phase for the sorption of Tm(III) ions was found to be 3:1 v/v, respectively. The sorption rate of metal ions on PUF is followed a first order kinetics and obeyed the equation for an intra particle diffusion process. The equilibrium concentration data of Tm(III) ions could be described satisfactorily by several adsorption isotherms. The Freundlich adsorption isotherm constants 1/nand K_Fare 0.66±0.02 and (5.7±0.3)^. 10^-3mol^. g^-1, respectively. The Langmuir isotherm constants for monolayer coverage (Q) and binding strength of sorption (b) are (2.5±0.7)^. 10^-5mol^. g^-1and (1.6±0.1)^. 10⁴l^. mol^-1, respectively. The sorption capacity derived from Dubinin-Radushkevich (D-R) isotherm is (1.7±0.2)^. 10^-4mol^. g^-1and the sorption free energy (E) is 9.8±0.2 kJ^. mol^-1indicating chemisorption phenomena. The thermodynamic parameters indicate that the sorption of Tm(III) ions onto PUF is endothermic, entropy driven and spontaneous in nature.     

A theoretical investigation of intermolecular interaction of a phthalimide based “on–off” sensor with different halide ions: tuning its efficiency and electro-optical properties

The interaction between chemosensor, N-(2-methyl-1,3-dioxo-indan-5-yl)-benzamide (1) and different halide ions (F ^? , Cl^? and Br^?) has been investigated using density functional theory (DFT). A clear insight of the sensor anion binding process has been presented. Our calculations revealed that the observed colorimetric and fluorescent signals are induced due to the ground state deprotonation of the sensor molecule caused by F^? which has two times higher binding affinity than other halide ions (Cl^? and Br^?). Derivatives of system 1 have been made to find a better sensor with higher binding affinity and longer wavelength of absorption. All the derivatives are better sensors than the parent 1 except 4-methyl-N-(2-methyl-1,3-dioxo-indan-5-yl)-benzamide (2). Among these derivatives, trimethyl-[4-(2-methyl-1,3-dioxo-indan-5-ylcarbamoyl)-phenyl]-ammonium (8) and (5-benzoylamino-1,3-dioxo-indan-2-yl)-trimethyl-ammonium (9) showed a change to higher binding energies of about 58 Kcal/mol and longer absorption wavelengths of 53 nm after deprotonation process than the parent system 1 which is highly demanded in selective chemical sensing. Systems 8, 9 and their deprotonated zwitterionic forms (8z and 9z) have also been studied for their nonlinear optical responses. Systems 8, 9 showed significantly good first hyperpolarizability (β) of 84 × 10^?30 and 40 × 10^?30 esu, respectively. These β values increase in zwitterionic states up to 216 × 10^?30 and 109 × 10^?30 esu, respectively after deprotonation with F^?, representing a new signal of deprotonation.     

Structural,dielectric and electrical properties of zinc doped nickel nanoferrites prepared by simplified sol–gel method

Zinc doped nickel ferrite nanoparticles having the general formula Ni_1−xZn_xFe₂O₄ (x = 0.1, 0.2, 0.3, 0.4, 0.5) were prepared with simplified sol–gel method. The structural and dielectric properties of these samples sintered at 750 ± 5 °C were studied. X-ray diffraction patterns confirm the single phase spinel structure for prepared samples. The scanning electron microscope images indicated that the particle size of the samples lies in the nanometer regime. The dielectric constant (ε_r) and dielectric loss tangent (tan δ) of nanocrystalline nickel ferrites were investigated as a function of frequency and Zn concentration. The dependence of ε_r and tan δ on the frequency of the alternating applied electric field is in accordance with the Maxwell–Wagner model. The prepared samples have a lowest dielectric constant compared to the already reported samples of the same composition to the best of our knowledge. The effect of Zn doping on the dielectric properties of nickel ferrites is explained on the basis of cations distribution in the crystal structure.     

Investigation on novel thermoplastic poly(urethane-thiourea-imide)s with enhanced chemical and heat resistance

A new generation of segmented thermoplastic poly(urethane-thiourea-imide)s (PUTIs) was synthesized via reaction of polyethylene glycol and thiourea-based prepolymer with dianhydride as chain extenders. NCO-terminated prepolymer was synthesized from a new diisocyanate, 3-(3-((4-isocyanatophenyl)carbamoyl)thioureido)phenyl-4-isocyanatophenylcarbamate (IPCT), as a hard segment and PEG forming soft segment. The starting materials and polymers were characterized by conventional methods and physical properties such as solubility, solution viscosity, molecular weight, thermal stability and thermal behavior were studied. PUTIs showed partially crystalline structures. Weight average molecular weights of PUTIs (GPC measurements) were in the range of 1,68,694-1,97,035. Moreover, thermogravimetric analysis indicated that poly(urethane-thiourea-imide)s were fairly stable above 500 °C having T₁₀ of 521-543 °C. Investigation of the results authenticated the approach of introducing thiourea (using IPCT) and imide structure in polyurethanes for the improvement of thermal stability. In comparison to typical polyurethanes, these polymers exhibited better heat resistance, chemical resistance as well as processability.     

Chiral resolution of multichiral center racemates by different modalities of chromatography

It is a continuous chase of researchers to separate chiral racemates due to their dominance in the pharmaceutical industry, agrochemicals, and food additives. There are many analytical techniques which have been used to resolve one chiral center racemates, but, little the literature report is scanty for the resolution of multiple stereogenic center racemates. Therefore, in this article the efforts were made to describe the enantiomeric resolution of multiple stereogenic center racemates by different modalities of chromatography. The various modalities discussed are high-performance liquid chromatography, capillary electrophoretic chromatography, miceller electrokinetic chromatography, supercritical fluid chromatography, nanoliquid chromatography, and gas chromatography. Besides, the attempts have also been made to discuss the future challenges and prospectives of the enantiomeric resolution of multichiral racemates.     

Influence of Rare Earth Ho3+ Doping on Structural,Microstructure and Magnetic Properties of ZnO Bulk and Thin Film Systems

We have investigated the doping behavior of rare earth element holmium (Ho³⁺) in ZnO semiconductor. The structural, microstructure, and magnetic properties of Zn_1-xHo_xO (x=0.0, 0.04, and 0.05) thin films deposited on Si(100) substrate by thermal evaporation technique were studied. The ceramic targets were prepared by conventional solid state ceramic technique. The pallets used as target were final sintered at 900 oC in the presence of N2 atmosphere. The experimental results of X-ray diffraction (XRD) spectra, surface morphology, and magnetic properties show that the Ho³⁺ doped ZnO thin films has a strong influence on the materials properties. The higher angle shift in peak position and most preferred (101) orientation were observed in XRD pattern. These spectra confirmed the substitution of Ho3+ in ZnO lattice. The surface morphology and stoichiometry for both bulk and thin films were analyzed by scanning electron microscopy and energy dispersive spectroscopy. It was observed that grain size decreases with the increase of Ho³⁺. Room temperature ferromagnetism was observed for Zn_0.95Ho_0.05O films. The ferromagnetism might be attributed to the substitution of Ho ions for Zn²⁺ in ZnO lattices.     

Unsymmetrically substituted benzimidazolium based Silver(I)-N-heterocyclic carbene complexes: Synthesis,characterization and in vitro anticancer study against human breast cancer and colon cancer

The promising biomedical applications of silver complexes stimulated the researchers to test these compounds against cancer. The present research work was designed to achieve this goal. In this work, a series of 5-methyl benzimidazole based N-Heterocyclic carbene ligands and respective silver(I) complexes were synthesized and tested on cancer cell lines to assess their anticancer activity. Unsymmetrically substituted benzimidazole was found unique in its reactivity and generation of a single product during NHC ligand formation was only possible after two successive alkylations with same alkyl halide. The corresponding Ag(I)-NHC adducts were obtained by in situ deprotonation of the NHC ligands. Synthesized compounds were characterized by various physcio-chemical and spectroscopic methods. Single crystal X-ray diffraction study of complex 7 revealed its mononuclear structure. Preliminary in vitro anticancer study of azolium salts and respective Ag(I)-NHC complexes against human breast cancer (MDA-MB-231), colon cancer (HCT-116) and normal endothelial cells (EA.hy926) cells revealed that all the compounds are more cytotoxic to cancer cells than normal cells and the complexes are relatively more potent compared to the corresponding NHC ligands. It was found that increased chain length and presence of methyl substituent on benzimidazole ring enhance the biopotency of Ag(I)-NHC complexes. The synthesized compounds were further studied for pro-apoptotic mechanism of action via Rhodamine 123 test. The tested compounds were found to induce apoptosis via extrinsic mitochondrial pathway.