JOURNAL OF THE IRANIAN CHEMICAL SOCIETY(JICS)
Year:2015 | Volume:12 | Issue:6|Papers Count:20

A rapid, sensitive and reproducible HPLC method has been developed for enantioseparation of six non-steroidal anti-inflammatory drugs, which are acidic compounds: carprofen, fenoprofen, flurbiprofen, ibuprofen, indoprofen and ketoprofen. The effects of the mobile phase composition on retention times and resolutions of the analytes were studied. A column based on vancomycin immobilized by reductive amination to aldehyde functionalised silica was prepared in house and used. The prepared sorbent shows a great stability and selectivity over a range of pH (4-6), and the separation was carried out using the mobile phase composed of a mixture of 40 % of methanol in ammonium nitrate buffer (50 mM) at pH 5.0. Another mobile phase consisted of 50 % of methanol in phosphate buffer (5 mM) at pH 5.0 was also prepared and tested. The two mobile phases are the optimum conditions obtained. All experiments were conducted at flow rate 0.6 ml/min, using a UV detector wavelength at l=254 nm.

The flexibility and simplicity of stir bar sorption extraction (SBSE) have been combined with the selectivity of ion imprinted polymers (IIP) and a selective and fast extraction and preconcentration method for Ag(I) has been developed. The stir bar was coated with silver imprinted polymer using sol-gel technique in combination with double-imprinting concept. The retained silver was eluted with 250 mL thiourea solution (0.5 mol L-1) at a pH of 3.0-4.0 and was determined by flow injection-flame atomic absorption spectrometry. The factors affecting the separation and preconcentration of Ag (I) were optimized. Under the optimized conditions, the method exhibited a linear dynamic range of 0.5-50 mg L-1 with a detection limit of 0.04 mg L-1 and an enhancement factor of 196. A relative standard deviation of 3.2 % (n = 6) was obtained at the level of 20 mg L-1. The proposed method was successfully applied to the determination of silver in hair, nail and different water samples. The accuracy of the proposed procedure was verified by recovery experiments, independent analysis by electrothermal atomic absorption spectrometry (ET-AAS) and application of the method to the determination of silver in a certified reference material.

A novel lanthanide porphyrin [TbIII (H2TPPS) IV.H3O.2H2O] n (1) (H2TPPS = tetra (4-sulfonatophenyl) porphyrin) has been synthesized through a hydrothermal reaction and structurally characterized by single-crystal X-ray diffraction. Complex 1 is characterized by a three-dimensional porous open framework with the terbium atom coordinated by eight oxygen atoms to yield a distorted square anti-prism. TG-DTA measurements reveal that complex 1 is thermally stable up to 400 oC. Photoluminescence investigations show that complex 1 has an emission in the red region with a quantum yield of 1.7 % and a lifetime of 341 ms. CV-DPV studies discover one reductive potential of -0.36 V and one quasi-reversible wave with E 1/2=-0.82 V.

Five novel Cu (II) complexes derived from the condensation between 5-bromosalicylaldehyde (bs) and α-amino acids (L-alanine, L-phenylalanine, L-aspartic acid, L-histidine and L-arginine) were synthesized and characterized by their elemental analyses, thermogravimetric analysis, IR, mass and electronic spectra, conductance and magnetic measurements. Moreover, the stoichiometry and the stability constants of the prepared complexes have been determined spectrophotometrically using continuous variation and molar ratio methods. The obtained results indicated that the Schiff bases of the amino acids: L-alanine, L-phenylalanine, L-histidine and L-arginine behave as tridentate ligands. The ligands are coordinating with the Cu (II) via azomethine nitrogen, deprotonated carboxylate oxygen and phenolic oxygen. However, in the case of L-aspartic, the ligand acts as tetradentate due to the coordination of the second carboxylate group. Based on the studies of magnetic moments and electronic spectra, a square planar geometry has been proposed for all Cu (II) complexes except bromsalicylaldehydine aspartate complex which has a distorted tetrahedral structure. The representative Schiff bases and their Cu (II) complexes were tested in vitro for their antibacterial activity against two Gram-positive bacteria (Micrococcus luteus and Bacillus cereus) and one Gram-negative bacteria (Pseudomonas aeruginosa). All the complexes showed activity against the organisms more than the free Schiff base ligands and the activity increases with the increase in concentration of test solution containing the new complexes. Moreover, the interaction of the prepared Schiff base amino acid Cu (II) complexes with calf thymus DNA has been investigated by absorption spectra, viscosity and gel electrophoresis measurement and the mode of CT-DNA binding to the complexes has been explored. The investigated complexes exhibit cooperative binding and presumably intercalate into DNA and follow the trend: bsarc>bshc>bsalc>bsphalc>bsasc.

A series of tripodal nitrogen containing ligands including amidine and aminopyridines with extra oxazoline functionality were synthesized. The corresponding titanium complexes bearing such ligands were synthesized by diethylamine elimination route. Diethylamidotitanium trichloride [Et2NTiCl3] reacts with the functionalized anilines, 2-(4, 4-dimethyl-4, 5-dihydrooxazol-2-yl)-N-(2-fluorophenyl)-aniline (FOxH) and 2-(4,4-dimethyl-4,5-dihydrooxazol-2-yl)-N-(2-methoxyphenyl)aniline (MeOOxH), the amidine(E)-N’-(2, 6-diisopropylphenyl)-N-(2-(4, 4-dimethyl-4, 5-dihydrooxazol-2-yl) phenyl) benzimidamide ( Am OxH), and the aminopyridines N-(2-(4, 4-dimethyl-4, 5-dihydro oxazol-2-yl)phenyl)-6-(piperidin-1-yl) pyridin-2-amine (ApOxH) and N-(2-(4, 4- dimethyl- 4, 5-dihydrooxazol-2-yl)phenyl)-6-(2,4,6-triisopropyl phenyl)pyridin-2-amine (Ap*OxH), under diethylamine elimination to form the corresponding titanium trichlorides [FOxTiCl3], [MeOOxTiCl3], [AmOxTiCl3], [ApOxTiCl3] and [Ap*OxTiCl3] in excellent yields. These compounds were characterized by spectroscopic methods, and X-ray crystal structure analysis (selected complexes). Furthermore, their behavior in ethylene polymerization was explored. The complexes show moderate activity towards ethylene if activated with MAO. The observed PEs were analyzed by HT-GPC and were found to be of low molecular weight for the amidinate AmOxTiCl3 but of very high one (Mp up to 3.5 million g/mol) for the aminopyridinate Ap*OxTiCl3 titanium complex.

Using principal components as input of a multivariate calibration model always brings up the question what subset of PCs gives the best reliable regression model with the most predictability. In this current study, two different methods are presented and discussed for the determination of naproxen (NAP) in serum based on principal component regression. At the first step, the fluorescence landscapes of NAP in serum with excitation wavelengths from 235 to 293 nm and emission wavelengths in the range 320–420 nm were obtained. The resulted excitation emission fluorescence matrices were unfolded and subjected to principal component analysis, and a linear regression model was built to model the relationship between the extracted principal components (PCs) and the concentrations. Two approaches were applied to select the most relevant principal components: eigenvalue ranking and correlation ranking. The results of this study showed that the importance of each PC to the multivariate calibration is not correctly described by its eigenvalue, but by its influence on the prediction of the dependent variable. Since it is possible for a PC to have a low variance in original dataset (low eigenvalue) but a high correlation with the dependent variable, eigenvalue ranking selection should not be employed. The proposed method is an interesting alternative to the traditional techniques normally used for determining naproxen such as HPLC. Compared to HPLC method, the proposed EV-PCR and CR-PCR methods were rapid, easy and of low cost for the quantification of NAP in serum using simple UV–Vis spectrofluorimetry.

Nano  g-Fe2O3@SiO2-AlCl2 is synthesized and applied as a recyclable catalyst for cost-effective synthesis of amidoalkyl naphthols, from aldehydes, 2-naphthols, and amides (or urea). This heterogeneous catalyst enhances product purity and can efficiently be removed by an external magnet. Characterization of the catalyst is carried out by SEM, XRD, ICP, TGA, and VSM. The thermal solvent-free procedure offers advantages such as shorter reaction times, simple work-ups, excellent yields, and reusability of the catalyst.

In a unique approach, four-component synthesis of some pyrano [2, 3-c] pyrazoles by [ChCl] [ZnCl2] 2and [H-NMP] HSO4 as inexpensive and recyclable acidic ionic liquids were investigated. Excellent yields of products were obtained using both environmentally friendly safe ionic liquids. A comparative study of [ChCl] [ZnCl2] 2 as Lewis acidic ionic liquid and [H-NMP] HSO4 as Bronsted acidic ionic liquid was also carried out. The results showed that advantages of these ionic liquids were their low reaction time, lack of by-products and their reusability in comparison with reported basic ionic liquid.

Due to special effects of water such as abundant, environmentally benign, hydrogen bonding in the transition state and high cohesive energy density as well as negative activation volume; the use of water as a green solvent is emphasized in green chemical processes. Heterocyclic compounds play an important role in the treatment of many diseases and also are effective in biological processes. Multi-component reactions are powerful synthetic methods in construction of new organic molecules because in these methods product is formed as one-pot and reduced number of reaction separation steps. For these reasons, the synthesis of heterocyclic systems using a simple multi-component approach in water is investigated greatly in the recent years. In this review, multi-component reactions that have been used for the synthesis of heterocyclic compounds in aqueous media during the last two decades are described.

Detection and identification of chemical warfare agents and their precursors/reaction products in various environmental matrices are important tasks which are considered in chemical weapons convention (CWC). 2-[(2-chloroethyl) (alkyl) amino] ethyl alkyl methylphosphonates I and N-alkyl bis (2-(alkoxy-methylphosphoryloxy)amines II are covered under schedule 2.B.4 of CWC and have structures closely related to the nerve and blister agents. In fact, they are products of the reactions between these two different CWC scheduled compounds: nerve agents and nitrogen mustards. Ion fragmentations during mass spectrometry studies of these chemicals were investigated using electron ionization mass spectrometry. Structures of fragments were confirmed using EI-MS analysis of the deuterated analogs. Density functional theory was also used to show preferred fragmentation pathways. Mass spectrometric studies revealed some fragmentation pathways, such as, McLafferty-type and hydrogen rearrangements and elimination of chlorine, chloromethylene radical, alkene and HCl.

Synthesis of novel derivatives of imidazo [1, 2-a] pyrimidine from one-pot three-component reaction of aldehydes, 2-amino-benzimidazole, and a-tetralone in the presence of catalytic amount of p-toluene sulfonic acid under reflux condition in EtOH has been presented. The simplicity and safety of the process, high yields and short reaction times were the main advantages of this protocol.

A nitrite electrochemical sensor based on electrodeposition of zirconium dioxide nanoparticles on carbon nanotubes (MWCNTs) modified gold electrode was proposed. Scanning electron microscope and energy-dispersive X-ray spectroscopy analysis were used for the characterization of ZrO2/MWCNTs composite. Electrochemical experiments showed that the proposed ZrO2/MWCNTs composite-modified electrode exhibited excellent electrocatalytic properties for nitrite. The potential utility of electrodes constructed was demonstrated by applying them to the analytical determination of nitrite concentration. An optimized limit of detection of 0.3 mM was obtained at a signal-to-noise ratio of three and with a fast response time (within 3 s). Additionally, the ZrO2/MWCNTs/Au electrodes exhibited a wide linear range from 0.5 to 1,115.5 mM and high sensitivity. The simple fabrication, high stability, and low cost of the modified electrode are the promising features of the proposed sensor.

In this study, a simple, rapid, and an economical method has been proposed for the extraction, preconcentration, and determination of parabens (methyl-, ethyl-, and propylparaben) in different samples based on derivatization by acetic anhydride and preconcentration using air-assisted liquid–liquid microextraction in a single step. In this method, 1, 1, 2, 2-tetrachloroethane (extraction solvent) containing mL-level of acetic anhydride (derivatization agent) is injected into aqueous sample containing parabens and picoline (catalyst). The mixture of aqueous and organic phases is withdrawn into a glass syringe and then injected into the test tube for several times till a turbid solution is obtained. After centrifuging, 1 mL of the sedimented phase is injected into gas chromatography-flame ionization detector. The effect of catalyst volume, derivatization agent volume, extraction solvent type and volume, ionic strength of the solution, pH, and numbers of extraction on the extraction efficiency is investigated. Under the optimal conditions, the enrichment factors and enhancement factors for the parabens were obtained in the ranges of 310-353 and 2,484-5,298, respectively. Limits of detection were between 0.18 and 8.5 mg L-1. The method was found to be linear over the range of 10-10,000 mg L-1 with good coefficients of determination (R2 > 0.999). The obtained extraction recoveries ranged from 69 to 107 % and precision of the method, expressed as relative standard deviation (RSD %), was within the range of 4.0-13 %. The proposed method was successfully applied for determination of parabens in different samples such as cream, toothpaste, and mouthwash.

We have investigated the interaction of a COS molecule with a SiC nanotube by means of density functional theory calculations. A carbon or silicon atom of the tube was replaced by an Ag atom, exploring its effect on the interaction. Replacing a carbon and a silicon atom by an Ag atom increases and decreases the adsorption energy, respectively. We found that the carbon doping by Ag atom makes the nanotube a potential chemical sensor to the gaseous COS molecules.

Structural and thermochemical properties of boron-nitride analogues of organic azides and benzotrifuroxan, as novel high energetic nitrogen-rich precursors, were studied using M06-2X/6-311G (d, p) and B3LYP/6-311G (d, p) density functional methods. The influence of azido (N3) group was investigated for the stability, molecular volume, molecular surface area, crystal density, positive, negative and total average potentials, variances, average deviation and electrostatic balance parameter on the molecular surface. It was found that crystal density and enthalpy of sublimation of azidoborazines are distinctly augmented by increasing the numbers of azido substituents. Meanwhile, the stability of these compounds decreases significantly. The B-substituted azidoborazines are more stable than N-substituted ones. Crystal densities of B-substituted di- and triazidoborazines are also larger than N-substituted compounds. Since the condensed-phase enthalpies of formation of azidoborazines are more positive than nitro and nitraminoborazines, these compounds have greater detonation performance. Detonation pressure and velocity of both triazidotrinitroborazines and boron-nitride analogue of benzotrifuroxan are larger than 2, 4, 6-trinitrotoluene (TNT). Detonation performances of these compounds are also between cyanuric triazide and triazidotrinitrobenzene.

Proteins as a mediator in the interfacial interactions between cell and substrates play an important role in the regulation of cell functions. In this study, polycaprolactone (PCL) nanofibers were prepared using electrospinning apparatus to obtain substrates with various physical characteristics and the same chemistry. Electrospin processing parameters were designed by Taguchi method and their effects on PCL fiber properties evaluated. Scanning electron microscopy was used for visual observation of fiber diameter, size distribution and bead formation. Mechanical properties of each specimen including tensile strength and elongation at break were assessed by means of standard mechanical test machine and correlated to the spinning parameters. In addition, adsorption of serum protein to each sample was quantified by Bradford method. SDS-PAGE analysis confirmed these results and revealed a significant difference between protein adsorption (up to 250 %) for the fibers with the same chemical composition. Additional experiments confirmed that the degree of protein adsorption is improved on increasing the quantity of beads in the structures. It was also verified that with increasing the time of exposure from 1 to 24 h, higher amount of proteins were adsorbed. The selected sample with the average diameter of 274 nm without any bead exhibited the highest tensile strength (7.6 MPa) and the lowest amount of adsorption. The results indicated that electrospinning processing parameters change the physical characteristics of the fibers (diameter and bead) and also their biological performance such as protein adsorption as well as cell attachment and cell spreading.

We investigated geometric and electronic properties of pristine and Be2O2-decorated carbon nanocones (CNCs) in the presence and absence of an H2S molecule using density functional calculations. It was found that the H2S molecule is physisorbed on the pristine nanocone, but it presents much higher reactivity toward the decorated CNC by Be2O2 cluster. The addition of more H2S molecules has also been considered on the Be2O2/CNC surface. With the increase of H2S coverage, the interaction between H2S molecules and Be2O2/CNC becomes weaker, and up to four H2S molecules can be chemisorbed on the cone, in which adsorption energies ranged from -27.21 to -10.28 kcal/mol at the B3LYP/6-31G(d) level of theory. The results also indicate that decoration of the Be2O2 cluster on the surface of the cone induces some changes in electronic properties of the cone and its Eg is changed after the adsorption of H2S molecule.

An efficient procedure has been reported for the synthesis of 4H-pyrano [2, 3-c] pyrazoles in the presence of ZnS nanoparticles as a heterogeneous catalyst at the room temperature by grinding method. The ZnS nanoparticles were synthesized by hydrothermal method and characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and N2 adsorption-desorption isotherm analysis. The 4H-pyrano [2, 3-c] pyrazoles were obtained with high yields (87-97 %) in a short reaction time (5-21 min) under solvent-free condition. This method has advantages such as it is solvent free, uses simple grinding method that can be carried out at room temperature, requires short reaction times and production of pure products without any by product. The nanocatalyst can be easily recovered and reused for five runs without appreciable loss of its catalytic activity.

In this research, a simple method was developed for the separation and determination of L-tryptophan in aqueous solutions. The method consists of a solid-phase extraction (SPE) cleanup system utilizing a column packed with nickel–aluminum layered double hydroxide as a nano-sorbent, followed by a spectrofluorometric detection step. Some factors influencing the SPE efficiency, including pH, the sample flow rate, the elution conditions and the amount of nano-sorbent were evaluated and optimized. The selectivity of the presented SPE method with regard to L-tryptophan was studied in the presence of other amino acids and potentially interfering ions. Under optimum conditions, the calibration graph was linear in the range of 0.1-120.0 mg L-1 with a correlation coefficient of 0.9975. The limit of detection and relative standard deviation for L-tryptophan were 0.01 mg L-1 and 0.62 %, respectively. The maximum sorption capacity of the sorbent for L-tryptophan was 37.6 mg g-1. The method was successfully applied to determine L-tryptophan in several food samples with recoveries in the range of 96.2-104.2 % for the spiked samples.

In this paper, we have screened a library of two different series of compounds to identify potent lipoxygenase (LOX) inhibitors. A number of new biphenyl bis (benzenesulfonamides) 2–3, indol-3-yl-benzenesulfonyl and acetohydrazides 4-5 and indol-3-yl-hydrazinecarboxylate 6 were synthesized and evaluated in vitro for LOX inhibitory activity. Compounds biphenyl bis (benzenesulfonamide) 2aand indol-3-yl-benzenesulfonylhydrazide 4e presented the best anti-LOX activity within these series with IC50 values 96.31±0.18 and 81.21±2.14 mM, respectively. The results were confirmed with docking studies.