A simple and rapid high performance liquid chromatographic method with fluorescence detection for the estimation of fexofenadine in rat plasma--application to preclinical pharmacokinetics

A sensitive high performance liquid chromatographic (HPLC) method involving fluorescence detection was developed for the determination of fexofenadine (FEX), known to have low oral bioavailability, in rat plasma. In order to understand the effect of various chromatographic factors on the separation of analytes and to simultaneously optimize the resolution and analysis run time, a response surface method was used. The chromatographic separation was achieved using a Supelco C(18)-DB (250 mm x 4.6mm I.D./5 microm particle size) column with mobile phase comprising of ammonium acetate buffer and acetonitrile (63:37, v/v), delivered isocratically at a flow rate of 1.0 mL min(-1). Diphenhydramine was used as an internal standard (I.S.). The statistical evaluation of the method was examined and the method was found to be precise and accurate with a linearity range of 1-500 ng mL(-1) (r>0.9980). The intra- and inter-day precision studies showed good reproducibility with coefficients of variation (C.V.) less than 12.26%. The advantages of our method are small sample volume (100 microL), short time of analysis (13 min) and a simple sample extraction and clean-up as compared to the previously published methods. The established method provides a reliable bioanalytical methodology to carry out FEX pharmacokinetics in rat plasma.     

A highly atom economic, chemo-, regio- and stereoselective synthesis, and discovery of spiro-pyrido-pyrrolizines and pyrrolidines as antimycobacterial agents

The 1,3-dipolar cycloaddition of azomethine ylides derived from acenaphthenequinone and α-amino acids viz. proline, phenylglycine and sarcosine to a series of 1-methyl-3,5-bis[(E)-arylmethylidene]tetrahydro-4(1H)-pyridinones afforded novel spiro-pyrido-pyrrolizines and pyrrolidines chemo-, regio- and stereoselectively in quantitative yields. These compounds were screened for their in vitro activity against Mycobacterium tuberculosis H37Rv (MTB), multi-drug resistant Mycobacterium tuberculosis (MDR-TB) and Mycobacterium smegmatis using agar dilution method. Among the synthesized compounds, spiro-[2.2″]acenaphthene-1″-one-spiro[3.3′]-5′-(2-chlorophenylmethylidene)-1′-methyltetrahydro-4′(1H)-pyridinone-4-(2-chlorophenyl)hexahydro-1H-pyrrolizine (3e) was found to be the most active with a minimum inhibitory concentration (MIC) of 0.4 μg/mL against MTB and MDR-TB.     

Formation and Functioning of Bimetallic Nanocatalysts: The Power of X‐ray Probes

Bimetallic nanocatalysts are key enablers of current chemical technologies, including car exhaust converters and fuel cells, and play a crucial role in industry to promote a wide range of chemical reactions. However, owing to significant characterization challenges, insights in the dynamic phenomena that shape and change the working state of the catalyst await further refinement. Herein, we discuss the atomic‐scale processes leading to mono‐ and bimetallic nanoparticle formation and highlight the dynamics and kinetics of lifetime changes in bimetallic catalysts with showcase examples for Pt‐based systems. We discuss how in situ and operando X‐ray spectroscopy, scattering, and diffraction can be used as a complementary toolbox to interrogate the working principles of today's and tomorrow's bimetallic nanocatalysts.     

Comment on: “Exposed-key weakness of αη” [Phys. Lett. A 370 (2007) 131]

We show that the insecurity claim of the αη cryptosystem made by C. Ahn and K. Birnbaum in [C. Ahn, K. Birnbaum, Phys. Lett. A 370 (2007) 131] under heterodyne attack is based on invalid extrapolations of Shannon's random cipher analysis and on an invalid statistical independence assumption. We show, both for standard ciphers and αη, that expressions of the kind given by Ahn and Birnbaum can at best be interpreted as security lower bounds.     

Cobalt–Carbon Nanoparticles with Silica Support for Uptake of Cationic and Anionic Dyes from Polluted Water

Silica-supported hierarchical graphitic carbon sheltering cobalt nanoparticles Co-HGC@SiO₂ (1) were prepared by pyrolysis at 850 °C of [Co(phen)(H₂O)₄]SO₄·2H₂O complex with silica in the presence of pyrene as a carbon source under nitrogen atmosphere. Nanocomposites (2) and (3) were obtained by acid treatment of (1) with HCl and HF acid, respectively. The nanocomposites showed rough hierarchical carbon microstructures over silica support decorated with irregular cobalt nanospheres and nanorods 50 to 200 nm in diameter. The nanoparticles consist of graphitic shells and cobalt cores. SEM, EDAX and TEM elemental mapping indicate a noticeable loss of cobalt in the case of (2) and loss of cobalt and silica in the case of (3) with an increase in porosity. Nanocomposite (3) showed the highest BET surface area 217.5 m²g⁻¹. Raman spectrum shows defect D-band and graphitic G-band as expected in carbon nanostructures. PXRD reveals the presence of cobalt(0) nanoparticles. XPS indicates the presence of Co(II) oxides and the successful doping of nitrogen in the nanocomposites. Moreover, TEM elemental mapping provides information about the abundance of Si, Co, C, N and S elements in zones. Nanocomposite (1) showed maximum uptake capacity of 192.3 and 224.5 mg/g for crystal violet CV and methyl orange MO dyes, respectively. Nanocomposite (2) showed a capacity of 94.1 and 225.5 mg/g for CV and MO dyes, respectively. Nanocomposite (4) obtained after treatment of (1) with crystal violet proved successful adsorption of CV. Co-HGC (5) prepared without addition of silica has a capacity for CV equal to 192 mg/g, while it is 769.2 mg/g with MO. Electrostatics and π–π interactions of graphite and cobalt species in the nanocomposites with aromatic rings of cationic and anionic dyes are responsible for the adsorption. Yan et al. was the best model to describe column kinetics. The thomas column adsorption model showed that the maximum uptake capacity of (1) was 44.42 mg/g for CV and 32.62 mg/g for MO. for a column packed with 0.5 gm of (1) and dye concentration of 100 mg/L at a flow rate of 1 mL/min. The column was recycled three times with no noticeable clogging or degradation of nanocomposites. Thus, Co-HGC@SiO₂ adsorbents can be used efficiently to treat water contaminated with cationic and anionic dyes.     

Dipolar cycloaddition based multi-component reaction: Synthesis of spiro tethered acenaphthylene–indolizine–pyridinone hybrids

The stereoselective syntheses of novel dispiro acenaphthylene–indolizine–pyridinone hybrid heterocycles have been achieved through one-pot four-component domino 1,3-dipolar cycloaddition–Michael addition–air oxidation sequence of reactions.     

Isophorone‐boronate ester: A simple chemosensor for optical detection of fluoride anion

A highly selective isophorone‐boronate ester based chemosensor, ( 1 ) , having a dicyanovinyl moiety as a convenient colorimetric probe, has been designed. Different types of anionic analyte such as CH₃COO^?, ClO₄^?, Cl^?, F^?, PF₆^?, Br^? and HSO₄^? were tested and among them only highly nucleophilic F^? anion displayed significant response towards the sensor. Addition of the fluoride anion across the boron atom disrupts the π‐conjugation thereby shifts the absorption wavelength towards the redshift region due to the decrease in the HOMO‐LUMO energy gap and a colour change from yellow to blue is observed under visible light condition. The detection limit of this probe was calculated to be 3.25 × 10^—8 M for fluoride anion. The binding constants and the detection limits of the sensor were calculated using absorption titration studies. The silica gel TLC strips dip‐coated by the chemosensor ( 1 ) revealed a colour change from yellow to brick red to naked eye.     

The properties of Mn–CuFe2O4 spinel ferrite nanoparticles under various synthesis conditions

The structural, morphological, magnetic, dielectric, and gas analyzing properties are studied in CuFe₂O₄(Mn–CuFe₂O₄) substituted spinel ferrite nanoparticles synthesized via evaporation and automatic combustion. The obtained nanoparticles are established to possess a spherical shape. The smallest size of Mn–CuFe₂O₄ (~9 nm) nanoparticles is achieved at using automatic combustion. X-ray diffraction and Mössbauer spectroscopy reveal that the crystal lattice constant and the Mn–CuFe₂O₄ nanoparticle size are larger at augmenting the annealing temperature from 600 to 900°С. The dielectric permeability and losses of Mn–CuFe₂O₄ nanoparticles are studied at various synthesis conditions and temperatures of annealing. Various aspects of gas sensibility of synthesized Mn–CuFe₂O₄ nanoparticles are tested, as well. The maximum response to the presence of liquefied petroleum gas is 0.28 at the optimum working temperature of 300°C for Mn–CuFe₂O₄ nanoparticles obtained via automatic combustion and it is 0.23 at 250°C for deposited nanoparticles.

     

Thiazole-tethered biaryls as fluorescent chemosensors for the selective detection of Fe3+ ions

3-Amino-5-(thiazol-2-yl)-[1,1′-biaryl]-2,4-dicarbonitriles have been synthesized employing a facile one-pot pseudo four-component domino strategy. All these thiazole-tethered biaryls exhibited blue fluorescence under UV lamp. Based on the high relative quantum yield, three compounds namely, 4a , 4d , and 4i , were chosen to explore the metal interference studies. Against several metal ions, these three thiazole-tethered biphenyl probes were found to be effective fluorescent chemosensors for the selective and sensitive detection of Fe³⁺ ions with a lower detection limit of 0.18, 0.12, and 0.16 μM, respectively.