Resumo em Inglês:

The enantioselective synthesis of highly functionalized cyclohexa-1,3-dienes was achieved via an organocatalytic one-pot three-component domino reaction. In addition, a possible mechanism accounting for the reaction was proposed.

Resumo em Inglês:

The present work focused on the mineralization of herbicide glyphosate (N-(phosphonomethyl) glycine) (C3H8NO5P) in aqueous phase by Glidarc plasma following the orthophosphates released and the reduction of the total organic carbon (TOC). Furthermore, the effect of initial concentration, pH and the degradation process of glyphosate in the presence of Fe2+ were also examined. The results showed that the efficiency of degradation increased with the presence of ferrous ions as catalysts in aqueous medium and also the release of orthophosphate is more efficient in acid medium with pH range of 3.5-6.3. The kinetics of the release of orthophosphate and the TOC removal obey the first order rate law. The ninhydrin and orthophosphates tests showed that the degradation of glyphosate in water by Glidarc plasma was mainly by OH and NO attacked with C–N and C–P bond cleavage leading to complete mineralization.

Resumo em Inglês:

In this work we carried out a study covering conformational analysis, docking calculations and molecular dynamics (MD) simulations of six excited state intramolecular proton transfer (ESIPT)-fluorescent 2-(2'-hydroxyphenyl)-benzoxazoles, interacting with the Dickerson-Drew (d(CGCGAATTCGCG)2) dodecamer in B-DNA conformation. In the analysis of the molecular docking calculations, the derivatives with the -NH2 group in the phenolic ring presented the most favorable interaction energies with the DNA, and the scores were even more favorable for the ligands containing the -NO2 group as substituent in the benzoxazolic ring. In the analysis of the MD simulations, the complexes showed stable interactions, with minimal induced structural distortions in the DNA, being the largest increase of the Rise parameter when the ligands were intercalated, and also the unwinding of Twist. During all simulations, the ligands showed stable interactions with the oligonucleotide, without denaturation. Considering these interactions and the peculiar photophysical properties of this class of molecules, they could be used as biological probes.

Resumo em Inglês:

This study evaluates the interaction of volatile corrosion inhibitors (VCIs) of the amino group with the zinc or zinc oxide surface by means of computational calculations using density functional theory (DFT) and comparing with experimental methods such as electrochemical impedance spectroscopy (EIS) and wet chamber tests. The application of these methods allowed indicating the most promising VCI and understanding its mechanism of action. Thus, after the vaporization of VCI molecules, they condense on the surface and form a protective film or a film with oxidizing characteristic, thereby preventing the corrosive action of the chemical species present in the environment.

Resumo em Inglês:

The electrocatalytic oxidation of unsymmetrical dimethylhydrazine (UDMH) has been studied on a Prussian Blue modified carbon paste electrode (PBMCPE) by cyclic voltammetry technique. The results show that Prussian Blue acts as a suitable modifier for electron transfer in the oxidation of UDMH. A linear range of 3 × 10-5 to 1.15 × 10-3 mol L-1, with a limit of detection (3σ) of 1.6 × 10-5 mol L-1 was obtained using the amperometric method. The proposed sensor exhibited several advantages, including, namely, no interference from hydrazine, simple preparation, good stability and repeatability. Finally, the PBMCPE was successfully applied for determination of UDMH in water samples.

Resumo em Inglês:

The aim of this study was to obtain new films based on collagen-chitosan with and without silver for biomedical applications. Membranes with a thin transparent elastic structure were obtained and after immersion in silver nitrate new membranes with silver have been elaborated and their physicochemical properties were assessed using infrared spectroscopy as well as contact angle determinations, and sorption properties. The water absorption has permitted the evaluation of the diffusion coefficient for modified collagen membranes and the values were comparable with diffusion coefficient specific for human cornea. Adsorption and desorption studies of silver ions were investigated based on the concentration of the silver solution. This concentration was determined by an inductively coupled plasma spectrometer. Antimicrobial investigations performed on Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus bacteria and hemolytic properties assays have been evaluated measuring optical density. The enhancement of antibacterial activity of membranes with silver content was emphasized.

Resumo em Inglês:

The compound extraction is an important step before analyzing composition of samples with antioxidant capacity. Several extraction conditions can be employed (temperature, polarity of solvent and extraction time, for example), and the chosen variables exert great influence upon final results. Thus, in order to execute an efficient extraction, it is needed to manage them with rigor. In this work, a new device was designed and tested. The Prompt, TOugh and eCO-friendly (PTOCO) system is the first equipment in mini-scale that allows a good control of antioxidants extraction conditions. It is a simple and cheap device that only needs small amounts of sample and solvent to obtain sufficient volumes of extract for application in routine analytical methods. Twenty experiments from an experimental design were executed using only 0.5 g of oregano and 60 mL of water. The total antioxidant capacity assays, as well as the mass spectra, confirmed the extraction efficiency.

Resumo em Inglês:

A solid sampling electrothermal vaporization inductively coupled plasma optical emission spectrometry (ETV-ICP OES) method for determination of As, Cd, Cr, Cu, Mn, Mo, Ni, Pb, Pd, Pt, Rh, Ru and V in pharmaceuticals is proposed. Tricyclic pharmaceuticals were directly analyzed due to their difficult decomposition with acids. Pyrolysis and vaporization temperature, sample mass, and reaction gas (Freon) flow rate were evaluated. The effect of organic and inorganic compounds was evaluated for matrix matching. The limits of detection ranged from 0.04 µg g−1 (Cu) to 107 µg g−1 (As) and the relative standard deviation was lower than 10%. The investigated elements were not detected in the analyzed samples with the exception of Cr in cyclobenzaprine hydrochloride. Since there was no certified reference materials available for metals and metalloids in pharmaceuticals, the accuracy of the method was evaluated by an independent technique and by analyte recovery. Inductively coupled plasma mass spectrometry was employed for analyte determination after sample decomposition by microwave induced combustion. The agreement of the results found by both techniques was better than 87% and analyte recoveries ranged from 91 to 103%.

Resumo em Inglês:

A flow-injection spectrophotometric procedure was developed for screening organophosphorus pesticides. The method is based on the inhibition of acetylcholinesterase immobilized on controlled porous glass beads with acetylcholine chloride as the substrate. Methyl parathion, chlorpyrifos, malathion and dichlorvos have been tested. The analytical peak height for a given acetylcholine chloride concentration correlates linearly with the logarithmic concentration of the pesticides between 1.0 × 10-3 mol L-1 and 1.0 × 10-6 mol L-1. If bromine water is added to the pesticide solution, a dramatic increase is observed in the analytical signal, and correlations with the logarithm of the concentrations are observed from 1.0 × 10-3 to 1.0 × 10-10 mol L-1.

Resumo em Inglês:

Cloud point extraction was employed for the separation and preconcentration of cadmium and lead prior to the determination by thermospray flame atomic absorption spectrometry. Di-2- pyridyl ketone salicyloylhydrazone (DPKSH) was used as complexing agent and the cadmium and lead complexes were extracted from the aqueous phase by the Triton X-114 surfactant. The variables associated with the preconcentration (pH as well as DPKSH, surfactant and electrolyte concentration) were optimized by using a full factorial design with two levels, four variables and a central composite. Under the optimized conditions, a sample volume of 100 µL was introduced into a hot Ti tube at a flow rate of 0.6 mL min-1 and the integrated absorbance was measured. Calibration curves were obtained with linear ranges of 0.075-2.0 µg L−1 (Cd) and 2.5-100 µg L−1 (Pb). The detection limits of 0.04 µg L−1 (Cd) and 1.3 µg L−1 (Pb) (99.7% confidence level) were obtained. The proposed method was applied to hemodialysis solutions and water samples. The accuracy of the method was evaluated by analyzing a certified reference material (NIST CRM 1643e) and the results were in agreement with the certified values at a 95% confidence level according to t-test.

Resumo em Inglês:

Crystalline (BiO)2CO3 nanosheets were synthesized by a rapid one-step reaction via microwave-assisted hydrothermal method using urea as a morphology mediator and carbon source. The hydrothermal method combined with microwave heating allowed to obtain sheet-like (BiO)2CO3 particles at shorter reaction times when compared to the conventional heating hydrothermal method. The photocatalytic activity of the as prepared samples was evaluated towards degradation of Ponceau 4R (C.I. 16255) under artificial UV-Vis light irradiation. The results show that good photocatalytic efficiency can be obtained for powders prepared with reaction times as low as 2 minutes.

Resumo em Inglês:

Hyaluronic acid (HA) microparticles crosslinked with divinyl sulfone (DVS) are primarily used in viscosupplementation to restore the viscoelastic properties of synovial fluid in the treatment of joint diseases. The crosslinking degree provides the swelling and rheological properties required for injectable application and biological stability. In this work, we studied the effects of alkaline medium on the crosslinking performance between HA and DVS. The crosslinking degree was evaluated based on the modification of the swelling and rheological properties of HA microparticles crosslinked at 1/1 HA/DVS mass ratio. Stable microparticles were obtained by shearing in the narrow pH range of 11.79 to 12.63. The microparticles exhibited gel-like dynamic mechanical behavior in the frequency range examined. Alkalinity increased the swelling and decreased the viscoelasticity of the HA microparticles. Ultimately, the interplay between the chemical modification and conformation of HA chains may control viscoelasticity and swelling at the levels required for specific applications.

Resumo em Inglês:

Indigenous bacteria isolated from a crude oil sample from a deep water reservoir in the Pampo Sul Oilfield (Campos Basin-RJ, Brazil) were previously classified as strains of B. pumilus. However, their enzymatic activities with fluorogenic probes and rates of petroleum biodegradation were completely different. Some of the bacteria depleted n-alkanes, whereas others did not. Aromatic compounds reported to be recalcitrant were also biodegraded by some of these Bacillus strains, revealing their outstanding ability to deplete petroleum. Further classification using matrixassisted laser desorption/ionization-time-of-flight mass spectrometry (MALDI-TOF MS) followed by statistical analysis revealed that these strains could be clustered into three different groups, consistent with their enzymatic activity evaluation. A more accurate phylogenetic analysis using gyrB gene sequences confirmed the MALDI-TOF MS classification of three groups of strains and identified them as Bacillus safensis, B. cereus and B. thuringiensis.

Resumo em Inglês:

Iron nitroprusside (FeNP) particles have been synthesized from drop by drop (n-FeNP) and bulk mixing (BM) (b-FeNP) methods. FeNP particles obtained from both methods were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM). n-FeNP particles were used in constructing modified carbon paste electrode (CPE), which has been further used for electrochemical studies. The effect of pH and electrolyte cation on the electrochemical behavior of n-FeNP modified CPE has been studied in detail. Oxidation of nitrite and reduction of peroxodisulfate reactions have been electrocatalyzed at two redox centers of n-FeNP modified CPE. Based on the electrochemical experiments conducted and Tafel plots, mechanism for both the reactions has been proposed. Both the analytes were estimated in soil and ground water samples using n-FeNP modified CPE and the results were validated with the help of standard methods.

Resumo em Inglês:

Comprehensive two-dimensional gas chromatography has been successfully applied to the analysis of various organic contaminants; however, few studies report its use in the analysis of endocrine disrupting compounds. These compounds are suspected to cause dysfunction of the endocrine system in humans and animals. This work describes the development of a method to analyse dibutylphthalate, benzylbutylphthalate, nonylphenol and octylphenol in water using solid-phase microextraction (SPME) and comprehensive two-dimensional gas chromatography with a flame ionisation detector. The merit parameters of the comprehensive two-dimensional gas chromatography with flame ionisation detector method were weighed against a gas chromatography/mass spectrometry-single ion monitoring method of endocrine disrupting compounds analysis. The compounds were evaluated over a concentration range of 0.2 to 6.0 µg L-1 . The use of a two-dimensional chromatography method proved to be advantageous in analysing endocrine disrupting compounds, according to the observed increase of the signal relative to the noise and peak resolution.

Resumo em Inglês:

Polystyrene (PS) nanofibers incorporated with ion-pair (IP) reagent, e.g., sodium dodecyl sulfonate (SDSn), were developed as functional adsorbents for the solid-phase extraction (SPE) of ionic neurotransmitter such as 5-hydroxytryptamine (5-HT), prior to the determination by high performance liquid chromatography-fluorescence detection (HPLC-FLD). A comprehensive study was initiated to optimize the preconcentration step by exploring the main factors that affect the extraction/preconcentration efficiency of 5-HT, such as the composition of nanofibers, eluent and its volume, amount of adsorbent, pH and ionic strength. The validity of this method was investigated and optimal analytical performance was achieved including a wide dynamic range of 0.50-200 ng mL-1, detection limits of 0.50 ng mL–1 and precision (as RSD%) lower than 4% for both intra-day and inter-day assays. This method was then applied to the determination of 5-HT in human plasma with satisfactory results.

Resumo em Inglês:

New butyrolactones aspernolides C and D, along with two known butyrolactones (A and B) were isolated from the culture of the endophytic fungus Aspergillus versicolor. Their structures were elucidated on the basis of extensive spectroscopic analysis, including 1D and 2D nuclear magnetic ressonance techniques, and electronic circular dichroism. The butyrolactones aspernolides C and D were tested for their anti-tobacco mosaic virus activity. The results showed that butyrolactones aspernolides C and D exhibited moderate anti-tobacco mosaic virus activity with IC50 values of 64.2 and 88.6 μM, respectively.

Resumo em Inglês:

Packed bed reactors can be used as an interesting alternative on the bioreduction of β-ketoesteres mediated by immobilized microorganisms. Here in, we report our results on the bioreduction of ethyl 3-oxohexanoate by immobilized Kluyveromyces marxianus cells and tert-butyl 3-oxobutanoate by immobilized Rhodotorula rubra cells under continuous flow conditions leading the desired β-hydroxy esters corresponding in high yields and enantiomeric excess.

Resumo em Inglês:

Lignosulfonate is a type of natural polymer surfactant. Its capability to reduce the surface tension of aqueous solution depends on its adsorption configuration at the air/liquid interface. The dynamic surface tension, the air/liquid interfacial film properties of lignosulfonate at different solution concentrations, pH values and ionic strengths had been measured in the present work. The results showed that the adsorption equilibrium of lignosulfonate at the air/liquid cannot be achieved in a short period; the diffusion coefficient of lignosulfonate from the liquid to the air/liquid interface decreased with the increasing of pH value, while it increased with the increasing of ionic strength. Lignosulfonate could form soluble monomolecular film at the air/liquid interface, whereas the film was unstable. The stability of lignosulfonate monomolecular film became poor with the increasing of solution concentration, ionic strength and decreasing of pH value. Combining with our previous research results, the adsorption mechanism of lignosulfonate at the air/liquid interface was proposed.

Resumo em Inglês:

The synthesis of five quinolines 8-octyloxy-4-[4-(octyloxy)phenyl]quinoline and 6-alkoxy- 2-(4-alkoxyphenyl)-4-[(4-octyloxy)aryl]quinolines are described by three-component coupling reaction mediated by Lewis acid FeCl3 and Yb(OTf)3. 4-n-octyloxybenzaldehyde, anisaldehyde, 4-n-octyloxyaniline p-anisidine, and 1-ethynyl-4-heptyloxybenzene, 1-ethynyl-4-octyloxybenzene and 2-ethynyl-6-heptyloxynaphthalene are the reagents in this protocol. A Yb3+ catalyst resulted in higher yields of quinolines than Fe3+. Polarizing optical microscopy (POM) revealed that none of the quinolines were liquid crystals, even the more anisotropic. UV-Vis measurements of one of the quinolines in polar solvent show two absorption bands at 280 and 350 nm related to π,π* and n,π* transitions. No changes were observed to lower-energy absorption band (ε < 104 mol L-1 cm-1) related to n,π* transition. A laser flash photolysis study for one of the quinolines relates a main transient band at 450 nm with a lifetime of 2.6 µs in ethanol, which is completely quenched in the presence of oxygen. This transient band was assigned to triplet-triplet absorption of one of the quinolines, which is semi-oxidised in the presence of phenol. Radiative rate constants have been determined along singlet and triplet excited state energies (3.39 and 3.10 eV, respectively). The chemical structure of one of the quinolines was also unequivocally confirmed by single-crystal X-ray analysis.

Resumo em Inglês:

A 22 factorial design (two factors with two levels, in triplicate) was performed to investigate the influence of factors A (soybean oil content in supplemented diet, at 2.1 and 4.2%) and B (time of treatment, 15 and 30 days) in three responses [(a) total n-3 fatty acids; (b) n-6/n-3 ratio; and (c) polyunsaturated fatty acids (PUFA)/saturated fatty acids (SFA) ratio] from lipids of Nile tilapia submitted to experimental treatment. Normality of residuals was assessed through statistical tests. Factors A and B were significant in all obtained regression models, while AB interaction was not a significant contributor for PUFA/SFA response. ANOVA and response surfaces obtained from factorial design indicated best results in tilapia that received the diet containing 4.2% of soybean oil during 30 days.

Resumo em Inglês:

For the first time, the adsorption of pesticides such as azinphos-methyl and methamidophos by polyamidoamine (PAMAM) derivatives was studied. Amine groups of PAMAM (G4 and G5) were functionalized with different biomolecules such as folic acid, coumarine, arginine, lysine, and asparagine. Subsequently, the synthesized compounds were used to trap organophosphates (OP), and its affinity to do so was measured by high-performance liquid chromatography (HPLC). The obtained experimental data was compared with the interaction energy values obtained through a nanoinformatic methodology, by using conformational sampling through Euler angles and semi‑empirical quantum mechanical calculations. Both, the experimental and the in silico methodology can be employed to screen with high accuracy the molecular interactions between OP agents and the functionalized PAMAM. Furthermore, affinity results by HPLC and molecular dynamics were supported by in vitro enzyme acetylcholinesterase activity assays.

Resumo em Inglês:

An inexpensive and fast vanadium [(IV), (V)] speciation method was performed by using optical chemical sensor that incorporates lipophilized calmagite (Cal) with cetyl pyridinium chloride (CPC) as a suitable ligand on triacetylcellulose membrane in aqueous solutions prior to UV-Vis spectrometric determination. Absorbance decrease of the optode in pH 6 at 490 nm depended on the V(V) ion concentration. The V(IV) content was found after oxidation to V(V) at the mentioned conditions. Two aliquots of sample were used for speciative determination of V(V) and V(V) + V(IV) mixture. With the optimized proposed sensor V(V) and V(IV) can be assayed with detection limits of 0.002 and 0.003 nmol L−1, respectively. The optode was tested by analysing several mixtures containing different ratios of V(V) + V(IV) and was found to be highly reproducible. The validity of the method was checked via spiked water samples with total relative standard error less than 4%.

Resumo em Inglês:

Based on single factor experiments, a three level, four variable central composite designs were carried out to establish a quadratic regression model for the catalytic synthesis of isoamyl isovalerate over sulfonated organic heteropolyacid salts as a function of molar ratio of alcohol to acid, reaction time, the amount of water-carrying agent and the amount of catalyst. The optimum conditions were obtained as follows: n (isoamyl alcohol): n (isovaleric acid) = 1.1:1, amount of catalyst was 6.4% of acid, reaction time 2 h and water-carrying agent 10 mL. Under these conditions, the yield of isoamyl isovalerate reached 97.5%. The ionic liquid could be reused six times without noticeable drop in activity. Under optimum conditions, catalysts showed a superior catalytic efficiency and reusability due to better superacidity, lower molecular transport resistance and self-separation characteristics.

Resumo em Inglês:

A monolithic stationary phase based on 3-(methacryloxypropyl)trimethoxysilane monomer, prepared within a fused silica capillary externally coated with a UV-transparent fluoropolymer was employed for separation of estriol, 17-b-estradiol and progesterone by capillary electrochromatography in a standard mixture. A 23 factorial design was used to optimize the separation system. The optimized condition containing 30% (v/v) of acetonitrile and 10 mmol L-1 aqueous ammonium acetate presented a total run time less than 10 min by applying 25 kV. The resolution between adjacent peaks ranged from 1.8 up to 2.9 and the plate numbers per column meter in this condition was 1873, 3631 and 3886 for the estriol, 17-b-estradiol and progesterone peaks, respectively. The optimized method was employed in the quantitative analysis of a commercial transdermal emulsion formulation.

Resumo em Inglês:

Linear and non-linear quantitative structure-activity relationship (QSAR) models were presented for modeling and predicting anti-diabetic activities of a set of inhibitors of acetyl-CoA carboxylase 1 and 2 (ACC1 and ACC2). Different algorithms were utilized to choose the best variables among large numbers of descriptors and then these selected descriptors were used for non-linear (artificial neural network) and linear (multiple linear regression) modeling. The variable selection methods were consisted of stepwise-multiple linear regression (stepwise-MLR), successive projections algorithm (SPA), genetic algorithm-multiple linear regression (GA-MLR) and Bayesian regularized genetic neural networks (BRGNNs). The prediction abilities of the models were evaluated by Monte Carlo cross validation (MCCV) in variable selection and modeling steps. The results revealed that the best variables for describing the inhibition mechanism of ACC were among topological charge indices, radial distribution function, geometrical, and autocorrelation descriptors. The statistical parameters of R2 and root mean square error (RMSE) indicated that BRGNNs is superior for modeling the inhibitory activity of ACC modulators over the other methods. The sensitivity analysis together with the frequency of the selected molecular descriptors in this work can establish an understanding to the mechanism of ACC inhibitory activity of small molecules.