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Journal of the Chilean Chemical Society

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

[694 journals]

THEORETICAL STUDY OF THE STRUCTURAL AND ENERGETICS PROPERTIES OF THE INTERACTION SIDES OF GUANINE AND ADENINE IN GG AND AA TRANS BASE PAIRS
- Abstract: In the present work we have carried out an ab initio study on the structural and energetic properties of the hydrogen bonding formed between the different interaction sides of Guanine (G) and Adenine (A) in the GG and AA trans non Watson-Crick base pairs. The energies derived at the HF/6-31G(d,p) level, show that while Watson-Crick sides contribute significantly to the stabilization of the hydrogen bonding, however, Sugar and Hoogsteen sides interacciones are weaker. The inclusion of electronic correlation at the second order M0ller- Plesset perturbation method, confirm the importance of including this correlation at MP2/6-31G(d,p) and MP2/6-311G(d,p) levels. It is concluded that two Guanine molecules form hydrogen bonds energetically more favorable than AA pairs within the same kind of interaction, while those having the sugar-sugar GG interaction become better solvated in aqueous solution. The results also allow understanding the functional role of this type of interaction in the oligonucleotide.
MICROWAVE ASSISTED SYNTHESIS OF BIOLOGICALLY ACTIVE 4-HYDROXY-7V-(PHENYLCARBONYL)-2H-1,2-BENZOTHIAZINE-3-CARBOHYDRAZIDE 1,1-DIOXIDE DERIVATIVES
- Abstract: Microwave assisted synthesis of a series of 4-hydroxy-N'-(phenylcarbonyl)-2H-1,2-benzothiazine-3-carbohydrazide 1,1-dioxides from sodium saccharin is reported. Sodium o-benzosulfimide was N-alkylated with ethyl chloroacetate followed by base catalyzed ring expansion to six membered 1,2-benzothiazine through Gabriel-Coleman type rearrangement yielding ethyl 4-hydroxy-2H-1,2-benzothiazine-3-carboxylate 1,1-dioxide. It was later condensed with a series of benzohydrazides synthesized from various carboxylic acids to get the title compounds. All the synthesized compounds were subjected to preliminary evaluation for their biological activity against series of Gram positive, Gram negative bacteria and fungi. Some of the compounds showed marked activity against the selected microorganisms.
MODEL-BASED QUANTUM-CHEMICAL STUDY OF THE UPTAKE OF SOME POLYCHLORINATED POLLUTANT COMPOUNDS BY ZUCCHINI SUBSPECIES
- Abstract: We report the results of a search of formal relationships between accumulation data and molecular structure for some pollutant molecules (polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans and polychlorinated biphenyls) in Gold Rush, Black Beauty and Patty Green zucchini subspecies. We employed a model-based quantum-chemical approach and Linear Multiple Regression Analysis to correlate local atomic reactivity indices with accumulation capacities. We found several statistically significant relationships involving local reactivity indices, namely total and local atomic superdelocalizabilities, Fukui indices and net charges. This study, contrary to statistically-backed ones, is able to provide a microscopic insight of the mechanisms involved in the uptake process.
SYNTHESIS, COMPLEXATION AND BIOLOGICAL ACTIVITY OF NEW ISATIN SCHIFF_BASES
- Abstract: Some new Schiff-bases derived from condensation of 3-hydrazono-2-oxo-2,3-dihydroindol-1-yl)-acetic acid hydrazide (3) with benzaldehyde, p-methoxy-benzaldehyde and p-chlorobenzaldehyde have been synthesized in high yields via refluxing in EtOH in the presence of catalytic amount of acetic acid. The synthesized compounds have been characterized by elemental analysis, IR, iH-NMR and mass spectra. Cu(II), Zn(II), Mn(II) and Fe(III) complexes of the synthesized compounds were prepared and characterized by elemental analysis, conductivity measurements, IR, UV-Vis. spectra and magnetic moment measurements. TGA and DTA confirm the chemical formulation of the complexes and their thermal decomposition were evaluated. Antimicrobial activity of the synthesized compounds have been screened using the desk diffusion method with different strains of bacteria: Staphylococcus aureus, Klebsiella pneumoniae, Escherichia coli and Proteus volgaris were used.
RAPID ANALYSIS OF FINASTERIDE IN BULK AND FORMULATIONS BY RP-HPLC-PDA METHOD
- Abstract: A simple, precise, rapid and accurate LC-MS compatible RP-HPLC-PDA method has been developed and validated for the estimation of Finasteride (FIN) in bulk and tablet formulations. The chromatographic separation was achieved on Phenomenex C18 column (150 mm x 4.6 mm, 5.0 µ particle size) using the mobile phase comprising 0.02% formic acid (in water): methanol in the ratio of 20:80 (v/v) at a flow rate of 1mL/min and FIN was eluted at 3.4 min. Quantification and linearity were achieved at 220 nm over the concentration range of 5-50 µg/mL and the percentage mean of assay was found to be 100.29. The method was validated for specificity, linearity, accuracy, precision, LOD, LOQ, stability and robustness as per the ICH guidelines and is suitable to be employed in Quality Control.
SYNTHESIS, CHARACTERIZATION AND ANTIMICROBIAL STUDIES OF CO-ORDINATION POLYMERS
- Abstract: A novel heteronuclear bis-ligand namely 5-[4-(2-carboxyphenyl carbonyl amino)-phenyl-4-carbonyl methyl amino)-8-hydroxyquinoline was synthesized and characterized. This Bis-ligand was designated as CPHQ. Co-ordination polymers of this CPHQ bis-ligand were prepared with Cu+², Co+², Ni+², Mn+² and Zn+² metal ions. All of these Co-ordination polymers and the CPHQ ligand were characterized by elemental analysis, IR, NMR spectral studies, thermogravimetry, electronic reflectance spectral studies and magnetic susceptibility measurement. The synthesized novel Bis-ligand and their Co-ordination polymers were screened for their antimicrobial activity.
ESTERIFICATION OF SALICYLIC ACID USING Ce⁴+ MODIFIED CATION-EXCHANGE RESIN AS CATALYST
- Abstract: The esterification of salicylic acid with methanol was carried out over a series of Ce4+modified cation-exchange resins. The effect of different reaction conditions was studied on the conversion of salicylic acid, and the optimal reaction parameters were obtained. The experimental results indicated that Ce(SC^A)Olx7 was an effective catalyst for the synthesis of methyl salicylate. The conversion of salicylic acid could reach 93.3% while its selectivity was more than 99.0%. SEM-EDS and TG-DSC analysis were employed to characterize the structure and property of the catalyst. Besides, the catalytic performance of Ce(SC^A)Olx7 in the esterification of salicylic acid with different alcohols was compared. The reusability of Ce(SC^A)Olx7 was also studied by using salicylic acid and methanol as model substrates. The mechanism was proposed for the esterification of salicylic acid with methanol over Ce4+modified cation-exchange resins.
GALVANIZED STEEL PRE-TREATED WITH HYBRID FILM CURED BY UV: INFLUENCE OF PHOTOINITIATOR CONCENTRATION ON THE CORROSION RESISTANCE
- Abstract: Several coatings have been proposed as an alternative to replacement processes based on hexavalent chromium. Among them stand out the hybrid films. Some hybrids films, with modified composition by the addition of photoinitiators, can be cured by ultraviolet system (UV). The UV cure is the instantaneous conversion of a reactive liquid in a solid induced by radiation, starting from the polymerization and cross-linking reactions of the chemical species. In order that reaction takes place through the action of UV radiation, it is necessary to add, in the composition of the hybrid film, a substance sensitive to this radiation called photoinitiator. The aim of this work is the preparation and characterization of hybrid films, cured by UV, from TEOS and TMSPMA alkoxide precursors, with addition of photoinitiators with different concentrations (1 and 2%) and without photoinitiator on galvanized steel. The films were characterized concerning the morphology, physicochemical properties and electrochemical behavior. The presence and the increase of photoinitiator concentration on hybrid films improved corrosion resistance of the system.
SPECTROPHOTOMETRIC DETERMINATION OF ESZOPICLONE IN PURE AND PHARMACEUTICAL FORMS
- Abstract: Six spectrophotometric methods for determination of eszopiclone have been developed, validated and applied for the assay of the drug in pharmaceuticals. Methods A, B, C and D are based on ion pair complexation of drug, in acidic buffers, with triphenylmethane dyes viz., Bromothymol blue(BTB), Bromophenol blue(BPB), Bromocresol green(BCG) and Bromocresol purple(BCP). The complexes are extracted into chloroform and absorbance is measured around at 415 nm as function of concentration of the drug. The stoichiometry of the complex is found 1:1 in each case. Method E depends upon charge transfer complexation of neutralized drug with iodine which produces iodide ion whose absorbance at 366 nm is measured as function of concentration of the drug. This complex, too, has 1:1 composition as determined by Job's method. Method F is developed on the basis of oxidation of the drug with alkaline KMnO4 which generates green colored manganate ion with 610 nm. As the intensity of green color increased with increasing time kinetics of the reaction is followed and calibration curves are constructed by using initial rate and fixed time methods. Excellent recovery studies with high accuracy and precession indicate that the methods can be successfully used in industries for the assay of drug in pure form and pharmaceuticals.
NOVEL SPECTROPHOTOMETRIC METHODS FOR THE DETERMINATION OF FLUCONAZOLE IN THE PRESENCE OF ITS OXIDATIVE DEGRADATION PRODUCT
- Abstract: Five sensitive, selective and precise spectrophotometric stability-indicating methods for the determination of fluconazole in the presence of its oxidative degradation product and in pharmaceutical formulations are developed and validated. Method A is a newly developed spectrophotometric one that is called ratio difference method by measuring the difference in amplitudes between 261.5 and 266.5 nm of ratio spectrum. Method B is a third derivative spectropho-tometric one, which determines peak amplitudes from 265.5-268nm (peak-peak). Method C is ratio subtraction method. Method D is the first derivative of the ratio spectra by measuring the peak amplitude at 269 nm. Finally, method E is the mean centering of ratio spectra method by measuring the peak amplitude at 266.5 nm. The proposed methods allow the determination of fluconazole in the presence of its oxidative degradation product over a concentration range of 50400 µg.mL-1 with mean percentage recoveries of 100.24±0.91, 99.91±0.52, 100.20±1.26, 99.79±0.69, and 100.77±0.72 respectively. The selectivity of the proposed methods is checked using laboratory prepared mixtures. The proposed methods have been successfully applied to the analysis of fluconazole in pharmaceutical dosage forms without interference from other dosage form additives and the results have been statistically compared with a reported method.
DEVELOPMENT AND VALIDATION OF LIQUID CHROMATOGRAPHIC METHOD FOR NAPROXEN AND ESOMEPRAZOLE IN BINARY COMBINATION
- Abstract: The present study reports the development and validation of a simple, economic and sensitive HPLC method for the concurrent determination of naproxen and esomeprazole in pharmaceutical formulations. Isocratic chromatography was performed with C-18 column and mixture of phosphate buffer (pH 6.1) and acetonitrile in ratio of (40:60, v/v) at 1.5 mlmin-1. The eluents were monitored at 302 nm using UV detector. The method was isocratic in the range of 9.38 to 300 µgml-1 for naproxen and 0.5 to 16 µgml-1 for esomeprazole. Validation of the method was performed by testing parameters like linearity, accuracy, precision, robustness, specificity, LOD and LOQ values. In the specificity the drugs were subjected to forced degradation studies like acidic, basic, oxidative and thermal stresses. Both the analytes were separated within three minutes. As the method separates the degradation products produced during forced degradation studies from the active analytes so it can be used not only for regular determination of naproxen and esomeprazole but also for their stability studies.
DESIGN, ADMET AND DOCKING STUDIES ON SOME NOVEL CHALCONE DERIVATIVES AS SOLUBLE EPOXIDE HYDROLASE ENZYME INHIBITORS
- Abstract: Drug discovery is a lengthy and costly process which aims at bringing in a novel therapeutic molecule for the treatment of various diseases. In the present study, a novel series of eighty chalcone derivatives [(4-substituted)- (4'-substituted)-3' substituted sulphonyl (2E)- 1,3-diphenylprop-2-en-1-one] were designed to inhibit soluble epoxide hydrolase enzyme (sEH). Lipinski's rule of 5 and absorption, distribution, metabolism, elimination and toxicity (ADMET) properties of the compounds were calculated using Molinspiration server and Accord for excel software respectively. All 80 compounds have passed the Lipinski's rule of 5 and only 20 compounds showed considerable ADMET properties. These 20 compounds were subjected to molecular docking studies using AutoDock 4.2 in order to rationalize the possible interactions between test compounds and the active site of human soluble epoxide hydrolase enzyme (1ZD3). Binding energy, intermolecular energy and inhibition constant were the main parameters taken into consideration in this study. The binding energies ranged from -6.07 to -7.89 kcal/mol, the inhibition constant ranging from 1.64 μΜ to 35.45 μΜ and intermolecular energy ranging between -9.38 kcal/mol to -6.97 kcal/mol. Hence, further pharmacophore optimization and in vivo studies are necessary to develop potent chemical entities that could inhibit the sEH enzyme.
TETRABUTYLAMMONIUM HEXATUNGSTATE [TBA]₂[W₆O₁₉]: A NOVEL HETEROGENEOUS CATALYST FOR ONE-POT SYNTHESIS OF HANTZSCH 1,4-DIHYDROPYRIDINES IN SOLVENT-FREE
- Abstract: A new method for one pot synthesis of Hantzsch 1,4-dihyropyridines was achieved by the reaction of aromatic aldehydes, ethyl acetoacetate and ammonium acetate at 80 °C in the presence of an isopoly tungstate ,tetrabutylammonium hexatungstate [TBA]2[W6O19], as an effective and environmentally friendly catalyst. An important advantage of this catalyst is the ease of separating it from the reaction mixture, as well as the fact that it could be recycled a number of times.
SIMULTANEOUS DETERMINATION OF AMBROXOL, GUAIPHENESIN AND LEVOSALBUTAMOL SULPHATE IN PHARMACEUTICAL FORMULATIONS WITH THE USE OF FOUR RAPID DERIVATIVE SPECTROPHOTOMETRIC METHODS
- Abstract: Four simple, rapid, accurate, precise, reliable and economical spectrophotometric methods have been proposed for simultaneous determination of ambroxol, guaiphenesin and levosalbutamol sulphate, in pure and pharmaceutical formulations without any prior separation or purification step. The methods are first derivative zero crossing spectrophotometry, simultaneous equation, derivative ratio spectra zero crossing and double divisor ratio spectra derivative method. Developed methods show best results in terms of linearity, accuracy, precision, LOD and LOQ for standard laboratory mixtures of pure drugs and marketed formulations. Common excipients and additives did not interfere in determinations of these APIs. Results obtained by the proposed methods have been statistically compared by means of student t-test.
PRECONCENTRATION AND DETERMINATION OF SHORT CHAIN MERCAPTANS IN THE PRODUCED WATER BY DISPERSIVE LIQUID-LIQUID MICROEXTRACTION AND GAS CHROMATOGRAPHY
- Abstract: This paper describes the preconcentration of short chain n-alkyl C1-C6 mercaptans in the produced water using the dispersive liquid-liquid microextraction. In the present experiments, 0.8 mL dispersive solvent (acetonitrile) containing 10.0 µL extraction solvent (carbon tetrachloride) was rapidly injected into the samples and followed by centrifuging and direct injection into the gas chromatograph equipped with flame ionization detector. According to the results, dispersive liquid-liquid microextraction gas chromatography flame-ionization detector was successfully used for determination of short chain n-alkyl C1-C6 mercaptans. The parameters affecting the extraction efficiency were evaluated and optimized. Under the optimum conditions, the figures of merits for six short chain n-alkyl C1-C6 mercaptans were determined to be 4.0-100.0 ng/L (n = 6, RSD = 6.8%), 6.0-80.0 ng/L (n = 6, RSD = 11.0%), 2.0-90.0 ng/L (n = 6, RSD = 2.6%), 5.0-120.0 ng/L (n = 6, RSD = 4.4%), 3.0-80.0 ng/L (n = 6, RSD = 9.2%) and 2.0-110.0 ng/L (n = 6, RSD = 6.5%), respectively.
SYNTHESIS, EXPERIMENTAL AND DFT STUDIES ON THE CRYSTAL STRUCTURE, FTIR, ¹H NMR AND ¹³C NMR SPECTRA OF DRIVATIVES OF DIHYDROPYRIDINES
- Abstract: Several derivatives of dihydropyridines are prepared through the condensation of aldehydes, dimedone and NH4OAc in H2O, in the presence of a catalytic amount of nano-Fe3O4. The crystalline products were characterized by FTIR, ¹H NMR and 13C NMR. Density Functional Theory (DFT) calculations at the B3LYP level is used to optimize the geometries of isolated molecules, and to calculate the, FTIR, ¹H NMR and 13C NMR spectra of selected synthesized compounds. We found that the DFT B3LYP calculated FTIR, ¹H NMR and 13C NMR spectra are in accordance with the experimental data.
SPECTROPHOTOMETRIC METHOD FOR RANITIDINE DETERMINATION IN DRUGS USING RHODAMINE B
- Abstract: A new spectrophotometric method has been developed for the determination of ranitidine hydrochloride (RHCl) in bulk drug and in tablet formulation. The proposed method involves the addition of a measured excess of bromate-bromide reagent in hydrochloric acid medium to RHCl, followed by determination of residual bromine by reacting with a fixed amount of Rhodamine B (RB) and measuring the absorbance at λmax=557 nm. Beer's law was found in the range of 0.3-3.2 μg ml-1 of RHCl, with a good correlation coefficient (r=0.9997). The limits of detection and quantification were calculated to be 0.08 μg ml-1 and 0.24 μmg ml-1, respectively. The different experimental parameters affecting the development and stability of the proposed method were carefully studied and optimized. The validity of the proposed method tested by analyzing the pure and pharmaceutical formulations and compared well with those obtained by the official method, demonstrated good accuracy and precision.
TRANSITION METAL COMPLEXES WITH LIGAND CONTAINING THIOAMIDE MOIETY: SYNTHESIS, CHARACTERIZATION AND ANTIBACTERIAL ACTIVITIES
- Abstract: A new series oftransition metal complexes of Fe(II), Co(II), Ni(II), Cu(II) and Zn(II) with the ligand 3-thionicotinoylaminodibenzofuran (L) were synthesized. The complexes were characterized by elemental analyses, metal content, spectroscopic methods (IR, UV-vis, NMR and EPR), conductivity and susceptibility measurements and by thermal studies. A quantum-mechanical interpretation of the electronic transitions for the free and coordinated ligand in the Ni(II) complex was performed using EHT-MO approach in order to get more information about the atoms involved in coordination to the metallic ion. According to all this information, we propose an octahedral geometry for Fe(II) and Co(II) complexes, a square-planar geometry for Ni(II) and Cu(II) complexes and a tetrahedral geometry for Zn(II) complex. The antibacterial activity of the ligand and its complexes was studied against selected bacteria Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa. It was found that all the complexes are antimicrobially active and show higher activity than the free ligand.
SPECTROPHOTOMETRIC AND FLUORIMETRIC METHODS FOR DETERMINATION OF NALTREXONE IN URINE, SERUM AND TABLETS BY OXIDATION WITH CERIUM (IV)
- Abstract: This paper proposes new methods for simple and sensitive spectrophotometric and fluorimetric determination of naltrexone (NALT) in tablet and biological fluids. The spectrophotometric method involve addition of a known excess of Ce(IV) to NALT in acid medium, followed by determination of residual Ce(IV) by reacting with a fixed amount of methyl orange, and measuring the absorbance at 510 nm. Fluorimetric method was based on the oxidation of NALT with Ce(IV) to produce Ce(III) and its fluorescence was monitored at 350 nm after excitation at 250 nm. In both methods, the amount of Ce(IV) reacted corresponds to the amount of NALT and the measured absorbance or fluorescence were found to increase linearly with the concentration of NALT, which are corroborated by the correlation coefficients of 0.9999 and 0.9996 for spectrophotometric and fluorimetric methods, respectively. Different variables affecting the reaction conditions such as the concentrations of Ce(IV), type and concentration of acid medium, reaction time, temperature, and the diluting solvents were carefully studied and optimized. The accuracy and precision of the methods were evaluated on intra-day and inter-day basis. The proposed methods were successfully applied for the determination of NALT in pharmaceutical formulation and biological samples with good recoveries.
DETERMINATION OF MINING ACTIVITY OF RIVER SEDIMENTS OF THREE CHILEAN BASINS BY PARTICLE INDUCED X-RAY EMISSION (PIXE)
- Abstract: Mining is one of the most important industrial activities in Chile and there is growing concern on pollution by some mining and metallurgical processes. We have studied the contents of heavy metals in sediments from three river basins in Chile. Samples were collected based on hydrologic criteria in six sites along the rivers in their path from the Andes to the Pacific Ocean. Particle induced X-ray emission (PIXE), was used to determine elemental concentrations, and enrichment factors were used to evaluate the significance of anthropogenic sources. The results indicate the presence of Si, Al and Fe as major components. Cu, Cr, Mn, Pb and Zn are the main trace elements. In the Aconcagua river basin, which has less mining activity, the elemental concentrations are within the range of normal crust. Instead, samples from Choapa and Cachapoal river basins present high enrichment factors, mainly in copper. This is consistent with the fact that copper mines operate in the area. A correlation of the values obtained to copper using ICP and PIXE technique was statistically acceptable. Therefore, determination of Cu in river sediment by PIXE allows identification of areas affected by mining activities in river basins of northern Chile.
SILICA SUPPORTED RHODIUM METAL NANOPARTICLES STABILIZED WITH (-)-DIOP. EFFECT OF LIGAND CONCENTRATION AND METAL LOADING ON THE ENANTIOSELECTIVE HYDROGENATION OF KETONES
- Abstract: Supported nanoparticles (NPs) in presence of chiral ligand (L) were synthesized for their use in enantioselective hydrogenation reactions. Catalysts were obtained by chemical reduction from rhodium chloride hydrate, RhCl3x3H2O, in presence of (-)-DIOP ligand ((4R,5R)-4,5-Bis(diphenylphosphino-methyl)-2,2-dimethyl-1,3-dioxolane) that allows to control NPs growing and to obtain solids having chiral surfaces. Chirally stabilized rhodium NPs on SiO2 were characterized using techniques such as: TEM, electron diffraction, EDS, nitrogen adsorption-desorption isotherms and XPS. This work includes the study of some variables such as metal loading and ligand concentration and their effect in metal core sizes, catalytic activity and enantioselectivity. Catalysts properties have also been evaluated in the hydrogenation of substrates: acetophenone (AP), 1-phenyl-1,2-propanedione (PPD), 3,4-hexanedione (HD), 2,3-butanedione (BD) and ethyl pyruvate (EP) as reaction test. Ligand plays a fundamental role in the synthesis of NPs and enantioselectivity in hydrogenations reactions. That is, due to it generates metal particle size < 5.8 nm compared with unstabilized systems that generate average diameter around 14 nm. Results indicate increased activity in catalytic systems obtained from the stabilization of NPs. Enantioselectivity levels reach values up to 53% due to the chiral ligand is on the catalysts surface.
CARBON-BASED SOLID ACID CATALYZED SYNTHESIS OF POLYHYDROQUINOLINE DERIVATIVES VIA HANTZSCH REACTION UNDER SOLVENT-FREE CONDITIONS
- Abstract: An easy method for the synthesis of polyhydroquinoline derivatives via one-pot four-component Hantzsch condensation of dimedone, aryl aldehydes, ethyl acetoacetate and ammonium acetate in the presence of a catalytic amount of carbon-based solid acid (CBSA) in solvent-free conditions is described. The main advantages of the present approach are relatively short reaction times, high product yields, clean reaction profiles, simple experimental and work-up procedure.
ELECTROCHEMICAL INCINERATION OF REFRACTORY ORGANIC POLLUTION BY ELECTROCHEMICALLY GENERATED FENTON'S REAGENT
- Abstract: The electro-Fenton process is an electrochemical method for waste water treatment based on the production of hydroxyl radicals via H2O2 generation in the presence of ferrous ions. The aim of this work is of applied Electro-Fenton technique to incinerate lubricate additive biocide N,N-methylenebismorpholine (C9H18N2O2).the effect of some operational parameters such as applied cathodic potential, the electrolysis time and aeration,concentration of supporting electrolyte on the generation of H2O2 was investigated. The optimal cathodic potential on the generation of H2O2 production was -500mV/SCE corresponding to a density current of 1.4 mA/cm², the production of hydrogen peroxide with the aeration and electrolysis time, then became stationary after 2h of electrolysis, the low pH favorite production of H2O2 electro generated. Whereas the Concentrations of supporting electrolyte of the solution have a slight affect. The degradation and incineration of N,N-methylenebismorpholine in the optimized parameters was also investigated (potential, current density, COD/Fe²+ ratio ) the result indicates that 97% of COD was incinerated at 50mA and the optimal concentration of catalyst is between 28 and 58mg/l.
DESULPHURIZATION OF LIQUID FUELS BY SELECTIVE ADSORPTION THROUGH MINERAL CLAYS AS ADSORBENTS
- Abstract: Different clays collected from local sources, including Kaolinite, Montmorollinte, Palygorskite and Vermiculite have been utilized for the selective adsorption of sulphur compounds prevailing in petroleum products i.e. crude oil, kerosene and diesel oil. The desulphurization activity of the clay was compared with the charcoal, ion exchange resins and with each other. Desulphurization was performed in batch operation at different time intervals i.e 1, 3 and 6 hrs at 40 ºC temperature. Out of different adsorbents used, Kaoilinte exhibited the maximum desulphurization yield of 60 %, 76 % and 64 % at 6 hrs adsorption incase of crude oil, kerosene and diesel oil respectively. All the mineral clays adsorbents were characterized by surface area, SEM and EDX analysis. The FT-IR study of the desulphurized fractions revealed that mostly high molecular weight thioles and thiophenic compounds were depleted during adsorption process.
KINETIC AND STOICHIOMETRIC EVALUATION OF FREE RADICALS SCAVENGERS ACTIVITIES BASED ON DIPHENYL-PICRYL HYDRAZYYL (DPPH) CONSUMPTION
- Abstract: Kinetics and stoichiometric measurements based on the reactions of stable free radicals are among the most employed procedures in the evaluation of antioxidant activities of pure compounds and complex mixtures. In the present work it is shown that initial rates of diphenyl-picryl hydrazyl (DPPH) consumption elicited by cinnamic acid derivatives are closely related to their reactivity towards peroxyl radicals. This implies that kinetic data regarding DPPH bleaching can be useful on the evaluation of antioxidant reactivities. On the other hand, data obtained at a single (long) reaction time are unrelated to the reactivity of the antioxidants and mostly reflect the number of phenol groups present in the tested sample.
A FACILE SYNTHESIS OF POROUS HEMATITE NANOMATERIALS AND THEIR FAST SORPTION OF CR (VI) IN WASTEWATER
- Abstract: Porous hematite (a-Fe2O3) nanomaterials can be simply acquired from amorphous iron (III) hydroxide (Fe (OH) 3) in neutral solution by an evaporation method in an open quartz flask in a vacuum drying oven. Results show that the as-obtained a-Fe2O3 particles at 180°C for 2h or so are nearly spindle in shape. Each of a-Fe2O3 microspindles is made of many ultrafine a-Fe2O3 nanoparticles and results in a porous structure. The as-prepared porous a-Fe2O3 powders have higher surface area (~78m²/g) and can rapidly remove Cr (VI) ions in wastewater at room temperature. The model of the adsorption kinetic of Cr (VI) is best adapted to the pseudo second-order equation.
DETERMINATION OF CHLOROGENIC ACID, BAICALIN AND FORSYTHIN IN SHUANGHUANGLIAN PREPARATIONS BY HPLC-DAD
- Abstract: High performance liquid chromatography coupled with diode array detection (HPLC-DAD) was developed for the simultaneous determination of three bioactive components - chlorogenic acid, baicalin and forsythin - in traditional Chinese medicinal Shuanghuanglian preparations. The analytes were extracted successfully using 80% aqueous methanol for 15 min in an ultrasonic bath. The optical chromatographic separation conditions were performed on a Finnigan Surveyor HPLC system with an Agilent Zorbax ODS C18 (4.6x150 mm, particle size 5 ìçé ) at 30 ºC using a gradient elution program with a mixture of acetonitrile and 0.2% phosphoric acid (v/v) as mobile phase within 25 min. Method validation results were obtained through the generation of calibration curves with the mixed standard solutions and a standard addition method, regression equations revealed linear relationships (correlation coefficients 0.9965-0.9985) between the peak area and concentration of the three analytes. The average recoveries were 90-106% (n= 6) with standard deviation below 3.37%. The developed HPLC assay was specific and could be readily utilized for comprehensive evaluation of Shuanghuanglian preparations.
CORROSION INHIBITION OF AA6061 AND AA6063 ALLOY IN HYDROCHLORIC ACID MEDIA BY SCHIFF BASE COMPOUNDS
- Abstract: N, N'-bis (Salicylidene)-1, 4-Diaminophenelyne (SDP) and N, N'-bis (3-Methoxy Salicylidene)-1, 4 Diaminophenelyne (MSDP) were synthesized, and their molecular structure were determined by FT-IR and ¹H NMR. The corrosion inhibitions of these compounds on AA6061 in 1M Hydrochloric acid were evaluated by weight loss method and scanning electron microscopic technique. The weight loss study showed that the inhibition efficiency of these compounds increases with increase in concentration and vary with solution temperature and immersion time. The various thermodynamic parameters were also calculated to investigate the mechanism of corrosion inhibition. The effectiveness of these inhibitors were in the order of MSDP> MDP. The adsorption of Schiff bases on AA6061and AA6063 alloy surface in acid obeyed Freundlich adsorption isotherm. The surface characteristics of inhibited and uninhibited alloy samples were investigated by scanning electron microscopy (SEM).
meso-TETRAPHENYLIRONPORPHYRIN(III) CHLORIDE CATALYZED OXIDATION OF ANILINE AND ITS SUBSTITUENTS BY m-CHLOROPERBENZOIC ACID
- Abstract: The most fascinating feature of heme-enzymes such as cytochromes P450 is their ability to carry out oxidations with high selectivity. Metalloporphyrin complexes are used as replicate compounds for cytochrome P450. A kinetic analysis has been carried out with the aim of understanding the mechanistic studies on oxidation of anilines by m-chloroperbenzoic acid catalyzed by meso-tetraphenylironporphyrin(III) chloride in aqueous acetic acid medium. The order of the reaction is found to be second order with respect to the substrate and first order with respect to the catalyst and oxidant. Product analysis proves that azobenzene is the sole product in the catalytic oxidation. The increase of [H+] in this oxidation retards the rate of the reaction. The effects of substituents on the oxidation rate are studied with 19 ortho-, meta- and para- substituted anilines at five different temperatures. The thermodynamic parameters for the oxidation have been determined and discussed. The catalysed m-chloroperbenzoic acid oxidation with substituted anilines fulfills the isokinetic relationship and Exner correlation but not to any of the linear free energy relationships. The solvent interaction also plays a major role in leading the reactivity. Based on the kinetic results and product analysis a probable mechanism is proposed.
AQUA MEDIATED ONE POT FACILE SYNTHESIS OF NOVEL THIOXO-1,2,4-TRIAZIN-5(2H)-ONE AND [1,2,4] TRIAZINO[5,6-A]INDOLE DERIVATIVES AND THEIR BIOLOGICAL ACTIVITIES
- Abstract: Rapid and highly efficient one pot green chemical synthesis of substituted 6-(2-aminophenyl)-4-(4-substitutedphenyl)-3-thioxo-3,4-dihydro-1,2,4-triazin-5(2H)-one and 8-substituted-3,5-dihydro-2H-[1,2,4]triazino[5,6-b]indole is carried out in aqueous medium under microwave irradiation. Improved synthesis of potent bioactive Schiff and N-Mannich bases of hexahydro-1H-indole-2,3-dione is also reported. The title compounds are easily accessible by various approaches; even waste free approaches have been developed. The operational simplicity, environmentally benign conditions and high yield achieved in a very short reaction time are major benefits that meet the requirements of green production, including saving energy and high efficiency. The results obtained under microwaves are compared with that of conventional heating. Structural assignments are based on spectroscopic data. Compounds have also been screened for antibacterial and antifungal activities.
SIMULTANEOUS ESTIMATION OF MOXIFLOXACIN HYDROCHLORIDE AND DEXAMETHASONE SODIUM PHOSPHATE IN BULK AND IN OPHTHALMIC SOLUTION BY RP- HPLC
- Abstract: A new simple, precise, accurate and selective RP-HPLC method has been developed and validated for simultaneous estimation of Moxifloxacin Hydrochloride (MOX) and Dexamethasone Sodium Phosphate (DSP) in Ophthalmic Solution. The method was carried out on a Qualisil RP C-8 (250 mm x 4.6 mm, 5 µm) column with a mobile phase consisting of Methanol: Water (75:25 v/v) pH adjusted to 3.0 with ortho-phosphoric acid of aqueous phase and flow rate of 1.0 mL min¹. Detection was carried out at 240 nm. The retention time for MOX and DSP was found to be 2.22, and 7.26 min, respectively. The MOX and DSP followed linearity in the concentration range of 10 - 60 µg mL-1 and 2- 12 µg mL-1 with r²= 0.99, respectively. The amounts of both these drugs estimated by proposed method were found to be in good agreement with label claim. The developed method was validated for sensitivity, accuracy, precision, ruggedness and robustness. The LOD and LOQ were found to be 0.30 µg mL-1 and 0.91 µg mL-1 for MOX and 0.10 µg mL-1 and 0.30 µg mL-1 for DSP. The proposed method can be used for routine analysis of both these drugs simultaneously in their combined dosage form.
IMMOBILIZATION OF GLUCOSE OXIDASE IN SILICA SOL-GEL FILM FOR APPLICATION TO BIOSENSOR AND AMPEROMETRIC DETERMINATION OF GLUCOSE
- Abstract: In this study, an electrochemical biosensor was developed by using a sol-gel coating solution. The modified platinum electrode used in the study was constructed by immobilization of glucose oxidase under a layer of sol-gel film. The sol-gel coating solution was prepared by using GLYMO, TEOS, and MTEOS. Electrochemical measurements were carried out amperometrically by determining hydrogen peroxide produced by the enzymatic reaction between glucose and glucose oxidase. The amperometric responses of the resulting enzymatic electrode to glucose were rapid. It was observed that the amperometric response of the enzymatic electrode was linear for glucose concentrations in the range from 2 to18 mM with 50 s response time. LOD and LOQ for the enzymatic electrode were calculated to be 0.055 mM and 0.184 mM, respectively. It was determined that the developed biosensor had an acceptable reproducibility. The selectivity of the biosensor was determined in the presence of some interfering substances, such as lactose, sucrose, urea, uric acid, oxalic acid, and ascorbic acid. The stability of the biosensor was investigated, and it was found that the sensor response decreased by 59% of its initial response over a period of 30 days of storage in dry conditions at 4 ºC.
IN VITRO CHARACTERIZATION OF ANTIOXIDANT PROPERTIES OF CUBAN ENDEMIC VARIETIES OF Erythroxylum alaternifolium A. Rich. ISOLATION OF TWO FLAVONOL GLYCOSIDES
- Abstract: The total antioxidant capacity from leaves of three Cuban endemic varieties of Erythroxylum alaternifolium was measured using three techniques: 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS+) and Oxygen radical absorbance capacity (ORAC). The highest values of antioxidant capacity and total phenols were measured in polar n-butyl alcohol extracts. Among the varieties of E. alaternifolium assayed, the var. parvifolium showed the strongest antioxidant capacity: ABTS (6.49 ± 0.05 mg TE/g dw); DPPH (11.16 ± 0.01 mg TE/g dw) and ORAC (35.1 ± 1.5 mg TE/g dw). Additionally, n-butyl alcohol extract of E. alaternifolium var. parvifolium also showed the highest content in phenolics with 284.2 ± 7.3 mg CAE/g dw and in flavonols with skeleton quercetin, kaempferol and myricetin with 471 μg/g dw. Moreover, two flavonol glycosides: ombuin-3-O-rutinoside and quercetin-3-O-rutinoside were isolated for the first time from n-butyl alcohol extract of E. alaternifolium var. alaternifolium.