Three Validated Methods for Simultaneous Determination of Ofloxacin and Dexamethasone in Binary Mixture

JPC – Journal of Planar Chromatography – Modern TLC - Three selective, precise, and accurate methods were developed and validated for the simultaneous determination of ofloxacin and...     

Synthesis of magnetite nanoparticles coated with polyvinyl alcohol for hyperthermia application

Journal of Thermal Analysis and Calorimetry - One of the main challenges in hyperthermia treatment is how to improve the heating performance of nanoparticles with high specific loss power (SLP). To...     

Electrophilic aromatic substitution by the fluorofullerene C60F18

The FeCl3-catalysed arylation of C60F18 gives tri-substituted compounds C60F15Ar3, where Ar=phenyl, 4-tolyl, 4-methoxyphenyl, 4-phenoxyphenyl, 4-chlorophenyl, 3,4-dichlorophenyl, 2-biphylenyl and 2-fluorenyl, together with some bis- and mono-substituted product. Bis-substitution was achieved with biphenylene and fluoranthene, and mono-substitution with biphenylene (2-position), pyrene (1-position), and naphthalene (1- and 2-positions); the tris-phenyl and tris-biphenylene derivatives are fluorescent. The 2-naphthyl substituent freely rotates at 328 K, whereas rotation of the 1-naphthyl substituent is prevented by interaction of the peri-hydrogen atom with fluorine. The 1-naphthyl derivative eliminates a molecule of HF during EI mass spectrometry, whilst the 2-naphthyl derivative eliminates HF and all fluorenes to give a naphthaleno[60]fullerene. The reaction rate is relatively unaffected by electron supply in the aryl rings, but no product was obtained with benzotrifluoride which defines the lower reactivity limit. The low discrimination between aromatics makes it possible to isolate derivatives having different aryl groups attached to the cage. Reactions occur mainly when the reagent solutions (or solutions in 1,2-dichlorobenzene) are evaporated to dryness. In most FeCl3-catalysed reactions, unreacted C60F18 was recovered, more if the less effective SnCl4 was used as a catalyst; use of AlCl3 resulted in polyarylation and degradation of the C60F18. The structure of C60F17(1-biphenylyl) was confirmed by single-crystal X-ray analysis. Reaction of C60F18 with perylene/FeCl3/o-dichlorobenzene gave red fluorescent "tagliatelli"-like threads (up to 1 cm long) of self-assembled pi-stacked tetrachloroperylene arising from chlorination by FeCl3.     

Tetronamides as latent acyclic vinylogous amides in formal aza-[3 + 3] cycloaddition reactions with alpha,beta-unsaturated iminium salts. An unexpected rearrangement and an approach to synthesis of substituted piperidines

A detailed account regarding formal aza-[3 + 3] cycloaddition reactions of tetronamides with alpha,beta-unsaturated iminium salts is described here. This investigation uncovers regioisomeric cycloadducts that were not found in previous studies involving this formal cycloaddition and an unexpected rearrangement that led to pyridines and dihydropyridines. Both stereochemical and regiochemical issues raised in this study provide further mechanistic insights into this cycloaddition. With careful control of reaction temperatures, the desired formal cycloadducts are obtained. Ensuing transformation of these cycloadducts into functionalized piperidines establishes the concept of employing tetronamides as latent acyclic vinylogous amides for the formal aza-[3 + 3] cycloaddition.     

Selective kinetic spectrophotometric method for determination of gatifloxacin based on formation of its N-vinyl chlorobenzoquinone derivative

A selective and simple kinetic spectrophotometric has been developed, for the first time, for the determination of gatifloxacin (GAT) in its dosage forms. The method was based on the formation of a colored N-vinyl chlorobenzoquinone derivative of GAT by its reaction with 2,3,5,6-tetrachloro-1,4-benzoquinone in presence of acetaldehyde. The formation of the colored product was monitored spectrophotometrically by measuring the absorbances at 655 nm. The factors affecting the reaction were studied and optimized. The stoichiometry of the reaction was determined, and the reaction pathway was postulated. Under the optimized conditions, the initial rate and fixed time (at 5 min) methods were utilized for constructing the calibration graphs. The graphs were linear in the concentration ranges of 2–100 and 10–140 μg ml^?1 with limits of detection of 0.84 and 3.5 μg ml^?1 for the initial rate and fixed time methods, respectively. The analytical performance of both methods was fully validated, and the results were satisfactory. The proposed methods were successfully applied to the determination of GAT in its commercial dosage forms. The label claim percentages were 99.7–100.5 and 98.2–99.5% for the initial rate and fixed time methods, respectively. Statistical comparison of the results with those of the reference method showed excellent agreement and proved that there was no significant difference in the accuracy and precision between the reference and the proposed methods. The proposed methods are superior to all the previously reported spectrophotometric methods in terms of the procedure simplicity and assay selectivity.     

Incoherent pion photoproduction on the deuteron including polarization effects

Incoherent pion photoproduction on the deuteron including polarization effects is studied in the energy region from π-threshold up to the Δ(1232)-resonance with inclusion of all leading πNN effects. For the elementary pion photoproduction operator, a realistic effective Lagrangian approach is used which displays chiral symmetry, gauge invariance, and crossing symmetry, as well as a consistent treatment of the spin-3/2 interaction. The interactions in the final two-body subsystems are taken in separable form. Effects of final state interaction are investigated and their role in unpolarized and polarization observables are found to be significant. The extracted cross sections and spin asymmetries are compared with available experimental data and predictions of other works, and a satisfactory agreement is obtained. In addition, the sensitivity of results to the elementary N(γ, π)N operator is investigated. Considerable dependence of the d(γ, π)NN results on the elementary amplitude is found. This indicates that it can serve as a filter for different elementary operators.     

A highly sensitive and specific polyclonal antibody-based enzyme immunoassay for therapeutic monitoring and pharmacokinetic studies of atorvastatin

This study describes the development and validation of a highly sensitive and specific enzyme immunoassay (EIA) for therapeutic monitoring and pharmacokinetic studies of atorvastatin (ATR). The assay employs a polyclonal antibody that recognizes ATR with high specificity and affinity, and ATR conjugated to bovine serum albumin (ATR-BSA) immobilized onto microwell plates as a solid phase. The assay involved a competitive binding reaction between ATR and the immobilized ATR-BSA for the binding sites on a limiting amount of the anti-ATR antibody. The bound anti-ATR antibody was quantified with horseradish peroxidase-labeled anti-immunoglobulin secondary antibody and 3,3′,5,5′-tetramethylbenzidine as a substrate for the peroxidase enzyme. The concentration of ATR in the sample was quantified by its ability to inhibit the binding of the anti-ATR antibody to the immobilized ATR-BSA and subsequent color development in the assay wells. The conditions for the EIA were investigated and optimized for the determination of ATR in plasma samples. The limit of detection was 0.04 ng mL^?1 and the effective working range at relative standard deviations (RSD) of ≤5% was 0.1–10 ng mL^?1. Mean analytical recovery of ATR from spiked plasma was 99.3?±?2.8%. The precision of the assay was satisfactory; RSD were 2.7–4.6 and 3.3–5.7% for intra- and inter-assay precision, respectively. The reliability of the EIA was confirmed by HPLC. The EIA is convenient, and one can analyze ～ 200 samples per working day, facilitating the processing of large-number of samples of ATR.     

Chemical constituents of Jordanian propolis

Seventeen compounds, including a new lanostane triterpenoid, 24(Z)-1β-3β-dihydroxyeupha-7,24-dien-26-oic acid, have been isolated from the methanolic extracts of two samples of Jordanian propolis collected from two different places with different dominant flora. The structures of the isolated compounds were elucidated by spectral methods including IR, UV, MS and 1- and 2-D NMR.     

On a quadratic fractional Hammerstein-Volterra integral equation with linear modification of the argument

We study the existence of monotonic solutions of a quadratic fractional Hammerstein-Volterra integral equation with linear modification of the argument. The quadratic integral equation studied below contains as a special case numerous integral equations encountered in the theory of radiative transfer and in the kinetic theory of gases. We show that the quadratic fractional Hammerstein-Volterra integral equation with linear modification of the argument has a monotonic solution in the Banach space of all real functions defined and continuous on a bounded and closed interval. The concept of measure of noncompactness and a fixed point theorem due to Darbo are the main tools in carrying out our proof.     

On existence and asymptotic behaviour of solutions of a fractional integral equation

We study the solvability of a quadratic integral equation of fractional order with linear modification of the argument. This equation is considered in the Banach space of real functions, defined, bounded and continuous on an unbounded interval. Moreover, we will obtain some asymptotic characterization of solutions.