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Journal of the Chilean Chemical Society

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Open Access journal
ISSN (Online) 0717-9324
Published by SciELO

[716 journals] [SJR: 0.207] [H-I: 16]

THE DIFFERENT RECOGNITION MECHANISM OF CARBAZOLE DERIVATIVES FOR BIOLOGICAL IMPORTANT ANION: THEORY AND EXPERIMENT
- Abstract: Two fluorescent anion sensors bearing phenol, carbazole-NH and -NO2 group were designed and synthesized. They both exhibited highly binding ability for H2PO4- among the anions tested. In the presence of H2PO4-, the fluorescence of the sensors underwent a dramatic enhancement, while the presence of other anions such as F-, AcO-, Cl-, Br-, and I-, had weak or no effect on the fluorescence. The determination limit of two sensors (1 and 2) toward H2PO4- were 3.0x10-7 and 5.0x10-7 molˑL-1, respectively. Theoretical investigation indicated it was the highest HOMO to induce the red-shift phenomena of two sensors.
SYNTHESIS, X-RAY CRYSTALLOGRAPHY, MOLECULAR DOCKING AND BIOLOGICAL SCREENING OF 2-AMINOPHENOL BASED SCHIFF BASES
- Abstract: Schiff bases, 2-{[(2-hydroxyphenyl)methylidene]amino}phenol (4) and 2-{[3-4-(dimethylamino)phenyl-2-propenylidene]amino}phenol (5), have been synthesized by the condensation of 2-aminophenol (1) with 2-hydroxybenzaldehyde (2) and 4-dimethylaminocinnamaldehyde (3), respectively. They showed good lipoxygenase inhibition and antioxidant activities, as compound 4 showed potent antioxidant activity. The products also showed good activities against Gram-positive: S. intermedius, B. subtilis and S. aureus, and Gram-negative: E. coli and S. typhi bacteria, as compounds 5 and 4 are excellent active against B. subtilis and S. typhi, respectively. These good to potent activities may be due to the presence of free hydroxyl and amino groups. They showed non-significant urease inhibition activity.
COVALENT IMMOBILIZATION OF GLUCOSE OXIDASE ON WELL-DEFINED POLYMER-SILICON WAFER HYBRIDS VIA SURFACE-INITIATED RAFT-MEDIATED PROCESS
- Abstract: A surface modification technique was developed for the functionalization of silicon surface with glucose oxidase (GOD). The silicon surface was first graft copolymerized with glycidyl methacrylate (GMA) via surface-initiated reversible addition-fragmentation chain-transfer (RAFT)-mediated process. GOD was then covalently immobilized through the ring-opening reaction between the amine groups of the GOD and the epoxide groups of the grafted GMA polymer chains. X-ray photoelectron spectroscopy (XPS) was used to characterize the surface-modified surface after each modification stage. Increasing the thickness of the polymer layer and the immobilization time could allow a great amount of GOD to be immobilized on the silicon surface. The GOD-functionalized silicon hybrids are promising candidates for the silicon-based glucose biosensors.
SYNERGISTIC INFLUENCE OF PROPARGYL ALCOHOL AND ZINC SULFATE ON INHIBITION OF CORROSION OF ALUMINUM IN 0.5M H₂SO₄
- Abstract: This paper describes the use of the Tafel polarization and electrochemical impedance spectroscopy technique (EIS) in order to study the corrosion inhibition process of aluminum in 0.5M H2SO4 solution in presence of propargyl alcohol and zinc sulfate at the open circuit potential (OCP) in the room temperature. The Nyquist diagrams consisted of a capacitive semicircle at high frequencies followed by a well defined inductive loop at low frequency values. The impedance measurements were interpreted according to a suitable equivalent circuit. The results obtained showed that the addition of the propargyl alcohol inhibits the sulfuric acid corrosion of the aluminum. The inhibition efficiency increases with an increase in the propargyl alcohol concentration. The inhibition occurs through adsorption of the propargyl alcohol on the metal surface without modifying the mechanism of corrosion process. The inhibiting action propargyl alcohol is considerably enhanced by addition of zinc sulfate. Both the inhibitors obeyed the Langmuir isotherm and the thermodynamic calculations revealed that the adsorption of inhibitors was of physical nature.
CRYSTAL STRUCTURES AND ANTIMICROBIAL ACTIVITIES OF N'-[2,5-DIHYDROXYBENZYLIDENE]-3,4,5-TRIMETHOXYBENZOHYDRAZIDE, N'-[2,4-DICHLOROBENZYLIDENE]-3,4,5-TRIMETHOXYBENZOHYDRAZIDE, AND 2,4-DICHLORO-N'-(2-HYDROXY-3-METHOXY-5-NITROBENZYLIDENE)BENZOHYDRAZIDE ETHANOL SOLVATE
- Abstract: Three benzohydrazone compounds, N'-[2,5-dihydroxybenzylidene]-3,4,5-trimethoxybenzohydrazide (1), N'-[2,4-dichlorobenzylidene]-3,4,5-trimethoxybenzohydrazide (2), and 2,4-dichloro-N'-(2-hydroxy-3-methoxy-5-nitrobenzylidene)benzohydrazide ethanol solvate (3), have been synthesized and structurally characterized by elemental analysis and X-ray single crystal structure determination. Compound (1) crystallizes in the orthorhombic space group Pbca, with unit cell dimensions a = 15.193(2), b = 11.086(2), c = 20.203(3) Å, V = 3402.8(8) Å3, Z = 8. Compound (2) crystallizes in the monoclinic space group P2(1)/c, with unit cell dimensions a = 17.127(3), b = 13.326(3), c = 7.984(2) Å, β = 99.689(2)°, V = 1796.2(6) Å3, Z = 4. Compound (3) crystallizes in the monoclinic space group P2(1)/n, with unit cell dimensions a = 12.919(3), b = 10.068(2), c = 15.205(4) Å, β = 98.288(2)°, V = 1957.0(7) Å3, Z = 4. X-ray crystallography reveals that each compound has an E configuration with respect to the C=N double bond and C-N single bond. The molecular structures of the compounds are stabilized by hydrogen bonds and weak πˑˑˑ π stacking interactions. The antimicrobial activities against Bacillus subtilis, Escherichia coli, Staphyloccocus aureus, and Bacillus magaterium were studied. The electron-withdrawing groups, such as Cl and NO2 are preferred groups for the antimicrobial material. Among the compounds, (3) showed the most effective activity against Escherichia coli, which is even stronger than the controlled drug Tetracycline.
A COMPARATIVE STUDY OF THERMODYNAMIC PROPERTIES OF STRUCTURALLY RELATED PHENOTHIAZINE DRUGS IN AQUEOUS SOLUTION
- Abstract: Association characteristics of amphiphilic phenothiazine drugs Fluphenazine and Trifluperazine dihydrochloride in water have been examined and their thermodynamic parameters have been calculated using conductometry. The electrical conductivity was measured as a function of concentration at various temperatures and cmc was calculated in the temperature range of 20-50°C. Thermodynamic parameters i.e. standard free energy of micellization, ΔG° , standard enthalpy of micellization, ΔH°m and standard entropy of micellization, ASm were calculated from cmc value using closed association model.
SIMULTANEOUS ESTIMATION OF ESOMEPRAZOLE AND LEVOSULPIRIDE IN BULK AND IN CAPSULE FORMULATION BY RP-HPLC
- Abstract: The present work deals with development and validation for simultaneous determination of Esomeprazole and Levosulpiride drugs in pharmaceutical formulations. A rapid, precise and specific reverse phase high performance liquid chromatography (RP-HPLC) method was developed for Esomeprazole and Levosulpiride. Chromatographic separations was achieved on a C-18 (5μm, 250x4.6 mm) HPLC column within a runtime of 10 min. Isocratic mobile phase contain methanol: buffer (pH 3) (65:35% v/v) and flow rate was maintained at 1.0 mL/min. Eluate was monitored at 260 nm. Levosulpiride was eluated at 2.7 min and Esomeprazole at 5.7 min. Linearity was studied in the concentratiosn range of 5 to 30 μg mL-1 and 10 to 60 μg/ mL for esomeprazole and levosulpiride respectively, with a correlation coefficient of 0.9995 and 0.9993 respectively. The method was validated according to the ICH guidelines with respect to specificity, linearity, accuracy, precision and robustness.
[PBMIM](FECL₄)₂ : AN EFFECTIVE CATALYST FOR THE ONE-POT SYNTHESIS OF 1, 3-DIHYDROPYRIMIDIN-2--ONES AND THIONES UNDER SOLVENT FREE CONDITIONS
- Abstract: An efficient, clean, and environmentally benign synthesis of 1,3- dihydropyrimidin-2- ones and thiones by one-pot three component reaction of substituted aromatic aldehydes, ethyl acetoacetate and urea/thiourea catalyzed by magnetic dicationic ionic liquid under solvent free conditions was described. This method provides several advantages such as environment benign, high yield, simple work up procedure and reusable catalyst. The magnetic ionic liquid could be readily separated from solution via application of an external magnet, allowing straightforward recovery and reuse.
RAMAN SPECTROSCOPY AND X-RAY FLUORESCENCE IN MOLECULAR ANALYSIS OF YELLOW BLOCKS FROM THE ARCHEOLOGICAL SITE PLAYA MILLER 7 (NORTHERN CHILE)
- Abstract: Yellow blocks from the archaeological site Playa Miller 7 (PLM7), on the coast of Atacama Desert in northern Chile, were analyzed by Raman spectroscopy and X-ray fluorescence (XRF) portable. Our results identify for the first time the use of K-jarosite and natrojarosite in prehispanic times (approx. 2500 year BP). In search of a possible source of supply for this mineral hydrothermal origin, our surveys were focused on Andean geothermal areas with identification, so far, from a single source in the region of Arica and Parinacota: Jurasi (JU), located at 4000 mamsl. Comparison of the Raman spectra between samples archaeological and Jurasi, allow us to infer that this hydrothermal source could be used as obtaining source of yellow pigment by prehispanic inhabitant of Formative period (3700-1500 years B.P.).
SULFONATED ORDERED NANOPOROUS CARBON AS AN EFICIENT SOLID CATALYST FOR THE SYNTHESIS OF PERIMIDINE DERIVATIVES
- Abstract: Sulfonated ordered nanoporous carbon (CMK-5-SO3H) efciently catalyzes the synthesis of perimidines using cyclocondensation of various aldehydes and ketones with 1,8-diaminonaphthalene in ethanol as a solvent at room temperature. This catalyst can be recovered and reused without significant loss of activity. This methodology provides a simple synthetic route to interesting classes of heterocycles in excellent yields at short time.
HIGH SPEED CENTRIFUGAL COUNTERCURRENT CHROMATOGRAPHY (HSCCC) ISOLATION AND IDENTIFICATION BY LC-MSⁿ ANALYSIS OF THE POLAR PHENOLICS FROM VASCONCELLEA QUERCIFOLIA
- Abstract: High speed centrifugal countercurrent chromatography (HSCCC) was successfully applied to preparative isolation of the main polar phenolics from the Peruvian Caricaceae Vasconcellea quercifolia A. St.-Hil. High-performance liquid chromatography with diode array (HPLC-DAD) and electrospray ionisation mass spectrometric detection (ESI-MS) was used to carry out a comprehensive characterisation of phenolic compounds from fruits and leaves of this plant. The main phenolics were the quercetin diglycoside rutin and the triglycoside manghaslin. Nine minor flavonoids were tentatively identified as kaempferol, quercetin, isorhamnetin and methoxymyricetin glycosides. HSCCC combined with other chromatographic methods allowed the isolation of the main phenolics from the plant. HPLC-DAD-MS analysis shows that the main phenolic compounds in V. quercifolia are similar to those described for V. pubescens but differs in the identity of the minor constituents.
STRUCTURAL AND THERMAL STUDY OF A NEW COORDINATION POLYMER POLY-BIS ( μ ₂ -BUTANE-1,2-DIYL BIS (PYRIDINE-3-CARBOXYLATE) K²N,N-SILVER(I) TETRAFLUOROBORATE
- Abstract: Reaction of L (L=butane-1,2-diyl bis(pyridine-3-carboxylate) with AgBF4 in a 1:1 ratio afforded crystals of [Ag(L)(BF4)]∞ which proved to be a one-dimensional linear polymeric chain. This compound crystallizes in the space group C2/c. In the crystal structure the linear chains are connected to another one via hydrogen bonds involving C15 as the donor atom, and O1 of the carboxylate group as the acceptor atom, thereby generating R²2(20) centrosymmetric rings to form a two-dimensional supramolecular aggregate. The thermogravimetric analysis shows that this compound is thermally stable up to 298 °C. The decomposition process is produced in one stage. The weight loss occurs from 298 to 780 °C, which is attributable to the complete removal of the ligand molecule and BF4 anion.
CO-DETERMINATION OF TWO ANTIPARASITICS DRUGS BY DERIVATIVE SPECTROPHOTOMETRY AND ITS PHOTODEGRADATION STUDIES
- Abstract: This work proposes a method for the co-determination of praziquantel and fenbendazole in veterinary pharmaceutical formulations (VPF) by second-derivative spectrophotometry at 226.4 nm (Zero-crossing method) and 324.6 nm (Graphic method), respectively. The excipients commonly used in VPF do not interfere. To obtain the optimal determination conditions, studies of solvent and light effects, were performed. The results of the light effects show that the expose of both drugs to indirect light and darkness does not produce any chemical change, since their zero-order spectra remained unchanged during the experiment. However, the exposition to the direct light only affects the fenbendazole. The zero order spectrum of FBZ in EtOH-HCl, present two broad bands (200 to 240 nm and 260 to 330 nm), these signals disappear and appear others totally different, at 230 nm and other with two peaks (285 and 295 nm). The FT-IR spectrum shows characteristics signals of the FBZ structure as the amide-NH group (3336.3 cm¹), this signal disappear indicating the bond break of the amide group caused by the exposition to sunlight for a time. These spectral changes evidenced a structural transformation as a result of photochemical decomposition in acid medium.
SYNTHESIS, SPECTROSCOPIC CHARACTERIZATION AND X-RAY ANALYSIS OF 6-NITROQUINAZOLINE-2,4(1H,3H)-DIONE
- Abstract: In this work, 6-nitroquinazoline-2,4(1H,3H)-dione was obtained in two step with good yields using a facile synthetic method. Its structure was characterized by X-ray single crystal diffraction technique (XRD), IR, 1D-NMR (¹H-NMR and 13C-NMR) and 2D-NMR (H-H COSY and H-C HMBC) spectroscopy. All N and O carbonyl atoms are involved in hydrogen bonding, with an average HˑˑˑO distance of 1.89(2) Å and N-HˑˑˑO angles in the range 169.5(2)-177.2(2)°. In the crystal packing the molecules are associated by two strong intermolecular N-H-O hydrogen bonds forming centrosymmetric ring with graph-set motif R²2(8), which are linked by N-HˑˑˑO hydrogen bonds.
KINETIC STUDY OF THE HYDROGENATION OF CITRAL ON Ir PROMOTED Au/TiO₂ CATALYST
- Abstract: A kinetic study of citral hydrogenation over an Au-Ir/TiO2 catalyst was performed with the aim to understand the effect of iridium on gold in this catalytic system. Au-Ir/TiO2 catalyst was prepared by co-deposition precipitation in an atomic ratio of 3/1. The effect of citral concentration, hydrogen pressure and temperature effect were also studied. The product distribution obtained is related with the proportion of Meδ+/Me0 sites. The deactivation of the catalyst occurs in the whole studied temperature range, 363 to 403 K, being more drastic as temperature increases due to the irreversible adsorbed CO blocks principally Ir0 sites. From initial reaction rates treatment an apparent global order close to 1 was determined. A Langmuir-Hinshelwood-type kinetic model involving the surface reaction as the rate limiting step between adsorbed citral and hydrogen on active sites with different nature shows good agreement with experimental initial reaction rates.
MODELING THE RELATIONSHIPS BETWEEN MOLECULAR STRUCTURE AND INHIBITION OF VIRUS-INDUCED CYTOPHATIC EFFECTS: ANTI-HIV-1 AND ANTI-H1N1 (INFLUENZA A) ACTIVITIES AS EXAMPLES
- Abstract: In this paper we tested the hypothesis that the building up of model-based methods to correlate molecular structure with the concentration required for the production of some biological effects such as giant cell formation, reduction of the number of viable cells, etc. is possible. We provide data supporting this model presenting structure-relationships results for two sets of molecules displaying inhibitory activity against some effects of HIV-1 and H1N1 viruses. The local atomic reactivity indices were calculated at the ZINDO/1 level of the theory. We found several statistically significant equations showing that some process is charge-, orbital- and/or steric-controlled. The main and most important conclusion is that the method, originally designed only for in vitro molecule-site equilibrium constants, nicely works for other properties like cytopathicity protection and cytostatic concentrations. This opens an entirely new research field and raises the possibility that this methodology be applied to other types of reports of biological activity data. We conjecture that this method is superior to the Hansch approach and that it is related in a still unknown form to the Hammett methodology.
PRELIMINARY ANTIPROLIFERATIVE EVALUATION OF NATURAL,-SYNTHETIC BENZALDEHYDES AND BENZYL ALCOHOLS
- Abstract: Vanillin, o-vanillin, natural and synthetic benzaldehydes and benzyl alcohols were assessed for antiproliferative effects using different human cell lines. Benzyl alcohols were synthesized from benzaldehydes reduced with NaBH4 in methanol solution. A new method for deprotection of ether compounds with TiCl4 solution was achieved with better performance, than previously reported. Twenty four compounds were tested. The in vitro growth inhibition assay was based on sulphorhodamine dye to quantify cell viability. Catechol 9 derived from piperonal as well as compounds 4 and 12 showed higher cytotoxicity on breast and prostate cancer cell lines (MDA-MB-231 and PC-3 respectively). o-Vanillin 5 has the highest cytotoxicity for all cell lines. IC50 values of 35.40 ± 4.2 μM Breast MDA-MB231; 47.10 ± 3.8 μM Prostate PC-3; 72.50 + 5.4 μM Prostate DU-145; 85.10 + 6.5 μM and Colon HT-29, were obtained without toxicity towards dermal human fibroblast (DHF cells).
COMPARISON OF DRY ASHING, WET ASHING AND MICROWAVE DIGESTION FOR DETERMINATION OF TRACE ELEMENTS IN PERIOSTRACUM SERPENTIS AND PERIOSTRACUM CICADAE BY ICP-AES
- Abstract: The work was to demonstrate a repaid, precise and accurate determination method for ten trace elements (Al, Cd, Cr, Cu, Fe, Mg, Mn, Ni, Se and Zn) in periostracum serpentis (PS) and periostracum cicadae (PC) by inductively coupled plasma atomic emission spectrometry (ICP-AES). In order to evaluate the best digestion method, three different sample digestion methods including dry ashing, wet ashing and microwave digestion procedures were compared in this study. Method validation was carried out through the generation of calibration curves with multi-element standard solutions and a standard addition method by using standard reference material (GBW 07604-Poplar leaves). The results revealed the microwave digestion procedures were the best sample digestion method because of dry ashing and wet ashing procedures without any advantages in terms of digestion efficiency than the microwave digestion procedures. Trace element contents in PS and PC samples presented a wide variability from the test results, and ten trace element contents in PC were found to be higher than in PS. Determination of trace elements by ICP-AES after microwave digestion was more sensitive and precise, which can be used for quality control and analysis of pharmacological effect in various ecdyses of some animal samples.
TWO NEW SCHIFF BASE NI^II AND CU^II COMPLEXES: SYNTHESIS AND STRUCTURES
- Abstract: Schiff base ligands 2-bromo-4-chloro-6-[(2-piperidin-1-ylethylimino)methyl]phenol (BCP) and 2,4-dibromo-6-[(2-morpholin-4-ylethylimino)methyl]phenol (DBP) and their nickel(II) and copper(II) complexes [Ni(BCP)2(CH3OH)2]2NO3 (1) and [Cu(DBP)2] (2), have been prepared and characterized by elemental analyses, IR, and single crystal X-ray crystallographic determination. The crystal of (1) is orthorhombic: space group Pbcn, a = 23.894(1), b = 8.244(2), c = 19.900(2) Å, V = 3919.9(10) Å3, Z = 4. The crystal of (2) is monoclinic: space group P2(1)/c, a = 7.072(2), b = 15.426(3), c = 14.214(3) Å, β = 96.718(2)°, V = 1540.0(7) Å3, Z = 2. The Schiff bases coordinate to the metal atoms through the phenolate O and imine N atoms. The Ni atom in (1) is in an octahedral coordination, and the Cu atom in (2) is in a square planar coordination.
NEW OPTICALLY ACTIVE ORGANO-SOLUBLE POLY(AMIDE-IMIDE)S FROM [N,N'-(4,4'-DIPHTALOYL)-BIS-L-AMINO DIACID]S AND 1,2-BIS[4,4'-AMINOPHENOXY] ETHANE: SYNTHESIS AND CHARACTERIZATION
- Abstract: Six new dicarboxylic acids 3a-f were synthesized by the reaction of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) 1 with L-amino acids 2a-f in a solution of glacial acetic acid/pyridine (Py) at refluxing temperature. Then six new optically active poly(amide-imide)s (PAI)s with good inherent viscosities were synthesized by direct polycondensation reaction of [N,N'-(4,4'-diphtaloyl)-bis-L-amino diacid]s with 1,2-bis[4,4'-aminophenoxy] ethane (APE) 4 in a medium of N-methyl-2-pyrrolidone (NMP)/ triphenyl phosphite (TPP)/ calcium chloride (CaCl2)/pyridine. Not only PAIs are optically active but also soluble in various organic solvents. These resulting new polymers can be used in column chromatography for the separation of enantiomeric mixtures. The resulted polymers were fully characterized by means of FTIR, ¹H-NMR spectroscopy, elemental analyses, inherent viscosity, specific rotation, solubility tests and UV-Vis spectroscopy. Also thermal properties of the PAIs 3a-f were investigated using thermal gravimetric analysis (TGA).
SOLVENT-FREE C-ALKYLATION OF BARBITURIC ACID IN THE NANOCRYSTALLINE MORDENITE MEDIA
- Abstract: A simple, efficient and clean procedure has been developed for the C-alkylation of barbituric acid. The Michael addition of barbituric acid to α,β-unsaturated esters by employing K2CO3 in the nano-mordenite media (K2CO3/nano-MOR), as catalyst, gave C-alkylated barbituric acid in good to excellent yield. Nano-MOR showed good reusability. K2CO3/nano-MOR catalyst has been found to be an excellent catalyst for the reaction under solvent-free conditions at 80-90 °C.
COMPARATIVE STUDY OF NEW SPECTROPHOTOMETRIC METHODS; AN APPLICATION ON PHARMACEUTICAL BINARY MIXTURE OF CIPROFLOXACIN HYDROCHLORIDE AND HYDROCORTISONE
- Abstract: Simple, specific, accurate and precise spectrophotometric methods were developed and validated for simultaneous estimation of Ciprofloxacin hydrochloride (CIP) and Hydrocortisone (HYD) in their pure form and pharmaceutical dosage form. Two new spectrophotometric methods were applied: extended ratio subtraction (EXRSM) and ratio difference (RDSM) methods. The results were compared to three well-established methods: Mean centering of ratio spectra method (MCR), Isoabsorpative point spectrophotometric method (IsoM) and Absorbance ratio method (ARM). The linearity range for the spectrophotometric methods was found to be (2-14 μg/mL) and (1-14 μg/mL) for CIP and HYD respectively. The selectivity of the developed methods was investigated by analyzing laboratory prepared mixtures of the two drugs and their combined dosage form. The results obtained from the proposed methods were statistically compared using one-way analysis of variance (ANOVA) where no significant difference was observed between the new (EXRSM and RDSM) and the well-established methods which prove their validity for the analysis of this binary mixture. The methods were validated as per ICH guidelines regarding accuracy, precision, repeatability and robustness; which were found to be within the acceptable limits. The new methods were simple, sensitive and don't need a special program, so they could be easily applied as alternative methods to LC methods in quality control laboratories lacking the required facilities for those techniques.
SPECTROPHOTOMETRIC DETERMINATION OF BISMUTH IN WATER SAMPLES BY DISPERSIVE LIQUID-LIQUID MICROEXTRACTION AFTER MULTIVARIATE OPTIMIZATION BASED ON BOX-BEHNKEN
- Abstract: A new simple and rapid dispersive liquid-liquid microextraction has been applied to preconcentration trace levels of bismuth as a prior step to its determination by spectrophotometric detection. In the proposed method, dithizone was used as a chelating agent, and tetrachloride carbon and ethanol are selected as extraction and dispersive solvent. The optimization strategy is carried out by using two level full factorial designs. Results of the two level full factorial design (2(4)) based on an analysis of variance demonstrated that the pH, concentration of dithizone, amount of dispersive and extraction solvents were statistically significant. Optimal condition for four variables: pH, concentration of dithizone, amount of dispersive and extraction solvents are obtained by using Box-Behnken design. Under the optimum conditions, the calibration graphs were linear in the range of 5-300 ng mL-1 with detection limit of 1.6 ng mL-1 (3δB/m) and the enrichment factor of this method for bismuth reached at 150. The relative standard deviation (R.S.D.) is 2.3% (n = 5, c = 50 ng mL-1). The method is successfully applied to the determination of trace amount of bismuth in water samples.
SYNTHESIS AND CHARACTERIZATION OF PCL/CALCINED BONE COMPOSITES
- Abstract: In this article, the hydroxyapatite and carbonate(HAC) nanoparticles were obtained by calcining the original pig bones, and the influence of different calcining temperature on morphology and size was investigated. Then, the polycaprolactone(PCL)/HAC composite materials were synthesized through in-situ polymerization with caprolactone(CL) and HAC. The effects of different weight ratios of HAC to CL on the performance of composites was discussed, and the morphology and microstructure of obtained composite materials were characterized by transmission electron microscopy(TEM), Fourier transform infrared(FT-IR) and (X-ray diffraction)XRD, etc. The results showed that HAC was uniformly dispersed in PCL matrix, and the composite material with HAC of 6 wt% was chosen for further application. This study provided a new way for synthesizing PCL/HAC materials that could be used for repairing and substituting for human damaged bone, which is significant in the theory and practice of bio-medicine.
KINETIC SPECTROPHOTOMETRY METHOD FOR THE DETERMINATION OF MORPHINE, NALBUPHINE AND NALTREXONE DRUGS IN BULK AND PHARMACEUTICAL FORMULATIONS
- Abstract: A novel study describes the development and validation of a selective and simple kinetic spectrophotometric method for the determination of some analgesic drugs namely, morphine (MOF), nalbuphine (NAB) and naltrexone (NAT) in bulk and in pharmaceutical formulations. This method was based on the reaction of the drugs under studying with alkaline KMnO4 to form a water-soluble bluish green colored product with a maximum absorbance at 605 nm. Although, the determination of MOF, NAB and NAT drugs by rate constant, fixed-concentration and fixed time methods were feasible with the calibration equations obtained, the fixed time method has been found to be more applicable. The fixed-time method is adopted for constructing the calibration curves, which were found to be linear over the concentration ranges of 4 - 18 μg mL-1 MOF, 2 - 20 μg mL-1 NAB and 2 - 16 μg mL-1 NAT. Different experimental parameters which can affect the development and stability of the color were carefully studied and optimized. The fixed time method of 20 min was further applied to pharmaceutical formulations of each drug and the percentage recoveries were 99.85±0.049 to 102.27±0.024. Statistical comparisons of the results with the reference methods show the excellent agreement and indicate no significant difference in accuracy and precision.
A FAST PROCEDURE FOR THE PREPARATION OF BENZIMIDAZOLE DERIVATIVES USING POLYMER-SUPPORTED WITH TRIFLUOROMETHANESULFONIC ACID AS NOVEL AND REUSABLE CATALYST
- Abstract: A highly selective synthesis of benzimidazoles from the reaction of o-phenylenediamines and aromatic aldehydes in the presence of PVP- trifluoromethanesul-fonic acid is reported, and morphological investigation was reported by FT-IR. The remarkable advantages of this method are the simple experimental procedures, shorter reaction times, high yields of product, and non-toxic catalyst. However, the reactions were performed in solvent-free and the catalyst could be reused for several runs.
ELECTROCHEMICAL DETERMINATION OF ETHYL MALTOL ON A GLASSY CARBON ELECTRODE MODIFIED WITH GRAPHENE
- Abstract: Ethyl maltol can be used to enhance the scent of foods. Its monitoring in foods is very important due to the potential harmfulness to human beings if large amounts of this flavor enhancer are ingested. A novel electrochemical method for the determination of ethyl maltol in food samples based on the electrochemical catalytic activity of graphene modified glassy carbon electrode is reported in this paper. The sensor exhibited excellent oxidation activity towards ethyl maltol. Using 1 mol L-1 NH3H2O-NH4Cl buffer solution (pH 8.0) as supporting electrolyte, ethyl maltol yielded a sensitive oxidation peak on the modified electrode. The influence of some experimental variables for EMA determination, such as supporting electrolyte, scanning rate, accumulation time and concentration of ethyl maltol, were studied. The oxidation peak current showed a linear relationship with the concentrations of ethyl maltol over the range between 6.0 x 10-7 and 1.0 x 10-4 mol L-1, with the detection limit of 1.0 x 10-7 mol L-1. The prepared electrode was used for EMA determination in beer samples with good results.
DATA ANALYSIS AND EVALUATION OF THE ELECTROCHEMICAL PARAMETERS FOR THE ET PROCESS VIA CONVOLUTIVE VOLTAMMETRY AND DIGITAL SIMULATION
- Abstract: Data treatment and determination of the standard heterogeneous rate constant of simple ET process (simple electron transfer) & number of electrons consumed in electrode reaction were carried out via convolution-deconvolution voltammetry and digital simulation methods. The working curves required for determination of the standard heterogeneous rate constant, k s, were constructed and discussed. The number of electrons, n, consumed in electrode reaction was calculated via simple method. The electro-reduction of Pb2+ was carried out at hanging mercury drop electrode while the redox behaviour of Fe3+ /Fe2+ couple was performed at glassy carbon electrode to confirm the validity of the reported method in calculation of k s and n in case of simple ET.
SYNTHESIS OF BIOLOGICALLY ACTIVE CHALCON ANALOGUES VIA CLAISEN-SCHMIDT CONDENSATION IN SOLVENT-FREE CONDITIONS: SUPPORTED MIXED ADDENDA HETEROPOLY ACID AS A HETEROGENEOUS CATALYST
- Abstract: Biologically active chalcones were synthesized via Claisen-Schmidt condensation of aldehydes with different ketones in solvent-free conditions using H5PMo10V2O40 supported on SiO2 as a reusable heterogeneous catalyst with excellent reusability.
SYNTHESIS OF STRUCTURALLY NOVEL CARBON MICRO/ NANOSPHERES BY LOW TEMPERATURE-HYDROTHERMAL PROCESS
- Abstract: Carbon spheres with two to four attached lobes having axial, trigonal and tetrahedral morphology were synthesized at considerably low temperature of 200 °C by a hydrothermal reaction. The source of carbon used was sucrose in sulfuric acid medium. The product obtained was characterized by X-ray diffraction, Fourier transforms infrared and Raman spectroscopy, which have inferred us the graphitic nature of the product. Further Scanning and Transmission electron microscopic studies have revealed the spheres having attractive morphology with attached lobes and nodes like structures. The carbon spheres are having the size ranging from 200 nm to 4 μrn. The spheres are solid balls exhibiting metallic luster. They possess surface area and pore volume of 2.956 m² g-1 and 0.616 x 10-2 cm³ g-1 respectively as obtained from Brunauer-Emmett-Teller method. The yield product obtained was about 70-80 %.
SINGLE-STEP SYNTHESIS, CHARACTERIZATION AND ANTIMICROBIAL STUDIES OF NOVEL STEROIDAL 1', 2', 3'- THIADIAZOLES
- Abstract: A convenient one-step synthesis of steroidal thiadiazoles 7-9 from steroidal 6-ketone semicarbazones 1-3 with thionyl chloride has been reported. The steroidal 6-ketone thiosemicarbazones 4-6 under similar reaction conditions also provided the same products 7-9. The structures of these newly synthesized compounds have been established on the basis of their IR, ¹H NMR and 13C NMR, elemental and analytical data. The synthesized compounds were screened for in vitro antimicrobial activity against different bacterial (gram positive and gram negative) and fungal strains. All the synthesized compounds showed significant activity against various micro-organisms.