Spectrofluorimetric methods of stability-indicating assay of certain drugs affecting the cardiovascular system

Two stability-indicating spectrofluorimetric methods have been developed for the determination of ezetimibe and olmesartan medoxomil, drugs affecting the cardiovascular system, and validated in the presence of their degradation products. The first method, for ezetimibe, is based on an oxidative coupling reaction of ezetimibe with 3-methylbenzothiazolin-2-one hydrazone hydrochloride in the presence of cerium (IV) ammonium sulfate in an acidic medium. The quenching effect of ezetimibe on the fluorescence of excess cerous ions is measured at the emission wavelength, λ_em, of 345 nm with the excitation wavelength, λ_ex, of 296 nm. Factors affecting the reaction were carefully studied and optimized. The second method, for olmesartan medoxomil, is based on measuring the native fluorescence intensity of olmesartan medoxomil in methanol at λ_em = 360 nm with λ_ex = 286 nm. Regression plots revealed good linear relationships in the assay limits of 10–120 and 8–112 g/ml for ezetimibe and olmesartan medoxomil, respectively. The validity of the methods was assessed according to the United States Pharmacopeya guidelines. Statistical analysis of the results exposed good Student’s t-test and F-ratio values. The introduced methods were successfully applied to the analysis of ezetimibe and olmesartan medoxomil in drug substances and drug products as well as in the presence of their degradation products.     

Semi-interpenetrating polymer networks synthesis by photocrosslinking of acrylic monomers in a polymer matrix

Semi-interpenetrating polymer networks have been obtained by UV-radiation curing of acrylate monomers dispersed in a polymer matrix, using an arylketone as photoinitiator. The polymerization kinetics was studied quantitatively by infrared spectroscopy for the various polymers examined: polyurethane, poly(vinyl chloride), poly(methyl methacrylate). The fastest reaction occurs in PVC films, where UV-curing develops extensively within a fraction of a second, leading to an insoluble and highly resistant material. The functionality of the acrylic monomer has a strong influence on the formulation reactivity, as well as on the mechanical and chemical properties of the final product. In PMMA, the polymerization was shown to continue to proceed efficiently for a few seconds after the UV exposure, even in the presence of air, due to both the high concentration of initiating radicals generated by the intense irradiation and the slow termination processes in solid media. © 1993 John Wiley & Sons, Inc.     

Asymmetric methoxyselenenylations and cyclizations with 3-camphorseleno electrophiles containing oxime substituents at C-2. Formation of an unusual oxaselenazole from an oxime-substituted selenenyl bromide.

Di[(1R)-2-Oximo-endo-3-bornyl] diselenide (4) and its benzoate derivative 5 were prepared from the corresponding known 2-keto diselenide 1. Treatment of 4 and 5 with bromine, followed by silver triflate in methanol-dichloromethane, generated the corresponding selenenyl triflates 6b and 7b. The latter reagents reacted with a variety of mono-, di-, and trisubstituted alkenes to afford the corresponding 1,2-addition products (beta-methoxy selenides) in a highly diastereoselective manner. The free oxime 6b was particularly effective in such methoxyselenenylations, giving diastereomeric ratios (d.r.s) ranging from 86:14 to > 98:2. Even cis-disubstituted alkenes, which typically give poor d.r.s in similar additions with other chiral selenium electrophiles, underwent highly stereoselective additions with this reagent. Reductive deselenizations of the adducts obtained from styrene and cis- and trans-stilbene provided the corresponding methyl ethers, whose absolute configurations were determined by comparison with authentic samples. As expected, the dominant enantiomers thus obtained from cis- and trans-stilbene, using either 6b or 7b, had opposite configurations. Moreover, each geometrical isomer of stilbene produced methyl ethers with the same configuration when treated with either the oxime 6b or the benzoate 7b. Coordination effects between the substituents at the 2-position of the camphor molecule and the positive selenium atoms in the intermediate seleniranium ions are believed to play an important role in determining the stereochemical outcome of methoxyselenenylations. Selenenyl triflate 6b and selenenyl chloride 7c were also investigated in the electrophilic cyclizations of several unsaturated alcohols and carboxylic acids. However, diastereoselectivities were typically much lower than in the methoxyselenenylations. When the selenenyl bromide 6a, derived from the addition of bromine to the corresponding diselenide 4, was allowed to stand in the absence of an alkene, it underwent intramolecular cyclization with the oxime hydroxyl group, followed by further bromination, to afford the unusual oxaselenazole 11, whose structure was determined by spectroscopic means as well as by X-ray crystallography.     

Electrodeposition of tellurium from phthalic acid bath

Electrodeposition of tellurium from metal salt solutions in the presence of phthalic acid and inorganic substances at controlled pH has been investigated. The current density ranged from 0.28 to 11.34 mA cm^–2. The percentage cathodic current efficiency was relatively low and increased with increasing concentration of tellurion ions in the bath. The purity of the deposited metal was better than 99%. X-ray diffraction analysis shows that the deposit belongs to the hexagonal structure.     

Invariant variational principles and conservation laws for some nonlinear partial differential equations with constant coefficients – I

The invariance under a one-parameter infinitesimal transformation groups [1] has been proven for a number of nonlinear partial differential equations (NLPDEs) with constant coefficients, which appear in a wide variety of modelling physical phenomena/applications. The invariance identities of Rund [2] involving the Lagrangian and the generators of the infinitesimal Lie groups are utilized, for writing down the conservation laws via Noether's theorem. In order that the study becomes more exhaustive, we have applied the above technique to the cases arising from the generalized Klein–Gordon equation by transforming it to ordinary differential equation (ODE), to get on exact solution for it.     

Subdominant critical singularities in the bcc Ising model

In order to analyze coalescing singularities using series expansion, a modification of the method introduced by Baker and Hunter is proposed. The Padé approximants on the Mellin transform are computed simultaneously for the initial series and its derivatives, allowing unbiased estimates for the critical parameters. The method is applied to the series generated by Nickel for various values of the spin in the bcc Ising model. We show that even with these longer series, the subdominant indices display large variation with the spin, and remain too small compared to the universal renormalization group prediction. However, the method does not detect other singularities in the temperature plane which are responsible for the observed discrepancy. Therefore the discrepancy is not significant.     

Normal modes of vibrations in CuBr

Phonon dispersion curves of CuBr have been measured at room temperature in the [001], [110] and [111] directions using inelastic neutron scattering. The results are interpreted in terms of a rigid ion model. Estimations are given for elastic constants.     

Preparation and optical properties of novel symmetrical hexadecachlorinatedphthalocyaninato zinc(II) spin coated thin films

Novel symmetrical 1,4,8,11,15,18,22,25-octahexyloxy-2,3,9,10,16,17,23,24-octa-(3,5- dichlorophenoxy)phthalocyaninato zinc(II) was synthesized and characterized by ¹H NMR, ¹³C NMR, MS, UV–Vis, XRD, and IR spectrometry. The synthesized ZnPc complex is soluble in various organic solvents such as CH₂Cl₂, THF, acetone, and ethyl acetate. This property helped to obtain thin films of the new ZnPc complex by spin coating method. The surface morphology of the thin films was investigated by atomic force microscopy, AFM, and showed that the molecules grow in stacks of rows. The spectrophotometric measurements of transmittance (T) and reflectance (R) spectra were carried out in the wavelength range 190–3000 nm.     

Polyphenol content and antioxidant activity of fourteen wild edible fruits from Burkina Faso

A total of fourteen (14) species of wild edible fruits from Burkina Faso were analyzed for their phenolic and flavonoid contents, and their antioxidant activities using the DPPH, FRAP and ABTS methods. The data obtained show that the total phenolic and total flavonoid levels were significantly higher in the acetone than in the methanol extracts.Detarium microcarpum fruit had the highest phenolic and the highest flavonoid content,followed by that of Adansonia digitata, Ziziphus mauritiana, Ximenia americana and Lannea microcarpa. Significant amounts of total phenolics were also detected in the other fruit species in the following order of decreasing levels: Tamarindus indica > Sclerocaryabirrea > Dialium guineense > Gardenia erubescens > Diospyros mespiliformis > Parkiabiglobosa > Ficus sycomorus > Vitellaria paradoxa. Detarium microcarpum fruit also showed the highest antioxidant activity using the three antioxidant assays. Fruits with high antioxidant activities were also found to possess high phenolic and flavonoid contents. There was a strong correlation between total phenolic and flavonoid levels and antioxidant activities.