Resumo em Inglês:

Chemically modified imidazole molecules: 4-(1H-imidazol-1-yl)aniline, 4-(1H-imidazol-1-yl)benzaldehyde, 4-(1H-imidazol-1-yl)phenol and (4-(1H-imidazol-1-yl)phenyl)methanol were investigated as inhibitors of the copper (Cu0) corrosion in 0.5 mol L-1 H2SO4 medium. The electrochemical corrosion data were obtained by monitoring open circuit potential, linear potentiodynamic polarization and electrochemical impedance spectroscopy techniques, while the computational density functional theory (DFT) method was applied to correlate the electronic properties of the molecules with corrosion inhibition efficiencies. All molecules had inhibited the Cu corrosion, and the inhibition values lied between 80 and 94%. A good correlation between the inhibition efficiencies values and Gibbs adsorption energy was found, showing that the more negative Gibbs energy, better interaction between the corrosion inhibitor with the Cu0 surface, diminishing its corrosion in 0.5 mol L-1 H2SO4 medium. The DFT calculations showed significative differences in electronic and reactivity properties of imidazole and other molecules. The higher corrosion inhibition of imidazole derivates could be explained by electrophilic characteristic of these molecules, since there are empty molecular orbitals spread over mainly in benzene rings that make a metal-ligand charge transfer, receiving electronic density from the copper surface by backbonding, according to the electronic Fukui functions and the potential charge distribution considering the map of electrostatic potential.

Resumo em Inglês:

Mari-mari (Cassia leiandra Benth.) is an Amazonian native fruit that is highly appreciated in the northern region of Brazil, but there are few studies regarding its chemical composition and/or biological properties. A phytochemical study was conducted on the extracts of the pulp, peel and seeds; and their antioxidant, cytotoxic and antimicrobial potential were also determined. Methanol and acetone extracts from different fruit parts were subjected to total phenolic, 2,2-diphenyl-1 picrylhydrazyl (DPPH) radical scavenging and FeIII reducing capacity (FRAP) assays. From the peel extracts, the engeletin and astilbin could also be isolated and characterized based on nuclear magnetic resonance spectroscopy and high-resolution mass spectrometry. A quantification using ultra-fast liquid chromatography of acetone dry crude extracts (DCE) of the peel showed that engeletin was the main compound (532.77 mg g-1 DCE). Astilbin content was also determined (131.53 mg g-1 DCE). The antibacterial and antiproliferative activities were evaluated and the methanol extract of the peel showed higher growth inhibition activity against all tested bacteria. Engeletin showed a relevant antimicrobial effect against Staphylococcus aureus, Staphylococcus epidermidis and Escherichia coli. Acetone and methanol peel extracts exhibited a relevant inhibitory effect on the proliferation of breast carcinoma cells (MCF-7), with no toxicity to the normal cell line (NIH/3T3).

Resumo em Inglês:

The worldwide emergence of viral diseases such as Zika, Dengue, Chikungunya, West Nile and Yellow Fever urge the search for solutions to eliminate their common vector, the Aedes aegypti mosquito. This paper describes the quantitative structure-activity relationship (QSAR) and docking studies of a series of nine 3-(3-aryl-1,2,4-oxadiazol-5-yl)propionic acids (AOPA), 1-9, previously published by our group. Additionally, three new 1,2,4-oxadiazoles, 10-12, have also been synthesized, characterized and studied. The QSAR and docking studies of all compounds, 1-12, clearly indicate that larger hydrophobic substituents such as biphenyl groups attached on position 3 in 1,2,4-oxadiazoles improve the larvicidal activity. It is worthwhile to mention that nanocapsulation of compounds 10-12 were necessary to help their dissolution in water and these three new 1,2,4-oxadiazoles also exhibited approximately equal or higher larvicidal activities compared to the former prototypes at stage L4.

Resumo em Inglês:

Chagas disease, caused by the parasite Trypanosoma cruzi, occurs most commonly in Latin America. As the treatment is highly toxic and ineffective in the chronic phase of the disease, alternative treatments are needed. Through quantitative structure-activity relationship modeling (QSAR) analysis using ligand-based and structure-based virtual screening methods, we predicted the trypanocidal potential of 47 neolignans against three targets, the enzymes cruzain, trypanothione reductase, and sterol 14-alpha demethylase. A combined analysis allowed for the selection of potent inhibitors against Trypanosoma cruzi. Of these compounds, two were isolated and shown to inhibit the growth of epimastigotes at concentrations of 9.64 and 8.72 µM, and trypomastigote forms at 4.88 and 2.73 µM. Therefore, the compounds (2R, 3R)-2,3-dihydro-2 (4 methoxyphenyl)-3-methyl-5-(E)-propenylbenzofuran (46) and ottomentosa (47) may be a good option of growth inhibitors for the parasite stages and warrant additional study.

Resumo em Inglês:

In this work, cellulose-based composite biofilms doped with silver nanoparticles (AgNPs) have been produced by eco-friendly process. The AgNPs were synthesized from Ilex paraguariensis with an average size of 45 nm, a characteristic plasmon band at 450 nm and zeta potential of -23 mV. The biofilm has been synthesized by casting method, using different volumes of AgNPs suspension with glycerol plasticizing agent (T6-T10) or not (T1-T5). The AgNPs were successfully incorporated into the biofilms, which was confirmed by scanning electron microscopy. The mechanical and optical structural and the antimicrobial properties of the biofilms have been determined. In the presence of AgNPs, the mechanical properties, thermal stability and water vapor barrier of the biofilms have not been altered. However, the addition of glycerol decreased the tensile strength and the modulus of elasticity, in addition to increasing the elongation of the biofilms and the water vapor barrier. The biofilm T10 showed a transmittance of ca. 10%, with high potential to be used as a UV light blocker. Finally, the biofilms doped with AgNPs showed activity against the bacterium Pseudomonas fluorescens. Given the above, this work presented a new biofilm with activity against the bacterium Pseudomonus fluorescens obtained by eco-friendly process.

Resumo em Inglês:

Here, we discuss the use of metal oxide films as charge transport layers in polymer light-emitting diodes containing poly(9,9-dioctyl-9H-fluorene-2,7-diyl) (PFO) as emissive layer. A simple device architecture consisting of glass-ITO | poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) | poly(9-vinylcarbazole) (PVK) | PFO | Ca | Al was used as starting point. This device assembly allows the investigation of basic properties of polymeric emitting layers, but does not provide stable devices with high performances. Thus, a more complex, multilayered diode structure is needed. We pursuit that goal with focus on the use of low-cost, easily processed materials. At one side, solution-processed non-stoichiometric MoOx films were used to replace the PEDOT:PSS as hole transport layer. At the other interface, solution-processed ZnO films containing either the bare oxide or a ZnO/carbon dots composite were introduced as electron transport layer. By tunning the characteristics of the metal oxide films, the performance of the blue-emitting PFO-based polymer light-emitting diodes (PLEDs) was massively enhanced.

Resumo em Inglês:

The approach proposed here is focused on the separation of light fractions (corresponding to fatty acids with molecular chains between 8 to 14 carbons) from the fatty acid methyl esters (FAMES) of the biodiesel obtained by the reaction of transesterification of triacylglycerols in the kernel gueiroba oil (Syagrus oleracea) with methanol. The whole biodiesel was fractionated through atmospheric distillation in a single glass column with thermal insulation. Such a separation produced 59.79% in volume of light biodiesel (LB), which was mixed with the standard mineral Jet-A1 kerosene (cf. ASTM, corresponding to the QAV-1, cf. the Brazilian standard of the ANP) for aviation, in the volumetric ratios LB:Jet-A1 2:98; 5:95; 10:90 and 20:80. The values of density, water content, distillation analysis, flash point, calorific value and freezing point were carefully checked for their compliance with the official recommendations for jet fuel. It was found that the mixtures richest in the Jet-A1 mineral kerosene, that is, those containing no more than 5% LB by volume, well meet the recommended standards and are technologically viable to replace pure Jet-A1 kerosene for the propulsion of turbine aircraft.

Resumo em Inglês:

Eugenia punicifolia (Kunth) DC, known as “pedra ume-caá” or “pitanguinha do cerrado”, is popularly used to treat infectious diseases like inflammation, and diabetes. Therefore, this study aimed to develop and validate an analytical method by high-performance liquid chromatography with diode array detector (HPLC-DAD) for the seasonal quantification of gallic acid (GA) and ellagic acid (EA), and to co-validate the method for quantification from the ethanol extract and fractions of the E. punicifolia leaves. Chromatographic separations were performed with a mobile phase gradient of acetonitrile/methanol/water acidified with 0.2% formic acid, a flow of 0.8 mL min 1, detection at 254 nm, and a C18 column (250 × 4.6 mm, 5 µm). Method validation parameters were determined following Brazilian legislation. The HPLC-DAD analytical method developed for the quantification of GA and EA was validated and demonstrated to be selective, linear, precise, accurate, robust, and without matrix effect. Accordingly, it is helpful for the analysis of these tannins in crude ethanol extracts and fractions from E. punicifoila leaves. Thus, our results may be of great help for quality control assessment and standardization of raw materials containing Eugenia punicifolia.

Resumo em Inglês:

The assessment of chlorine, fluorine, and sulfur concentrations in depth profile of drill cuttings was performed using ion chromatography after sample preparation by pyrohydrolysis. The parameters for pyrohydrolysis were optimized using a Box-Behnken design, and the established conditions were 300 mg of sample, 300 mg of V2O5, temperature of 1000 °C, reaction time of 25 min, and absorbing solution of 50 mmol L-1 NH3 + 150 mmol L-1 H2O2. The accuracy was evaluated by the analysis of certified reference materials and recovery tests, and the results showed a good agreement between determined and certified values and recoveries (89-108%). The precision (relative standard deviation (RSD) < 10%), and the limits of detection (0.5-2.5 mg kg 1) were suitable for drill cuttings analysis. The concentration of chlorine, fluorine, and sulfur in drill cuttings at different depths was at mg g-1 range, and its variation is related to the mineral composition of the samples.

Resumo em Inglês:

Rapid recognition of the sources of drugs can provide some valuable clues and the basis for determining the nature of the case. A novel recognition method was put forward to identify the sources of heroin drugs rapidly and non-destructively by using a hand-held near infrared (NIR) spectrometer and a multi-layer-extreme learning machine (ML-ELM) algorithm. In contrast to traditional linear discriminant analysis (LDA), support vector machine (SVM) and extreme learning machine (ELM) algorithms, the accuracy, sensitivity and specificity were the highest for the proposed ML-ELM algorithm. The prediction accuracy of the ML-ELM algorithm was 25.33, 20.00, 17.33% higher than that of LDA, SVM and ELM algorithm, respectively, for 4 cases. The ML-ELM models for recognizing the different sources of heroin drugs had the best generalization ability and prediction results. The experimental results indicated that the combination of the hand held NIR technology and ML-ELM algorithm can recognize the different sources of heroin drugs rapidly, accurately, and non-destructively on the spot.

Resumo em Inglês:

Interlaboratory comparisons (IC) present a challenge related to multivariate data analysis. ISO 13528:2015 is a reference document for interlaboratory comparisons. This standard does not provide descriptions of statistical methods for multivariate analysis and, according to our best knowledge, there is no practical guidance for the organizing and evaluation of multivariate data analysis for interlaboratory comparisons available. Due to this reason, some researchers have made efforts to develop methodologies that make it possible to analyze multivariate data in IC. Generally, these approaches are based on dimensionality-reduction methods like principal component analysis. This paper proposes a new approach to reduce the dimensionality of large data set and check the performance of laboratories based on multidimensional scaling (MDS) and robust confidence ellipse/ellipsoid (RCE). MDS is a multivariate analysis technique that allows grouping laboratories according to their similarity in a Euclidean space. On the other hand, RCE is a statistical method for outlier detection in a multivariate data set. In this work, it is proposed to combine MDS and RCE to evaluate laboratory proficiency in interlaboratory comparison. This methodology was compared with the multivariate z-score and both methodologies identified the same outlying laboratories. This preliminary result indicates that MDS/RCE is promising for classifying IC results.

Resumo em Inglês:

Hot potassium carbonate (HPC) process aims to remove the CO2 present on synthesis gas. This removal is done in an absorption process, where takes place the reaction of CO2 with a K2CO3 solution. This reaction is slow and H3BO3 can be used to increase the rate of reaction. The rate-based model is the most suitable way to model the process. This approach uses different correlations to calculate important mass transfer and hydraulic parameters, such as: mass transfer coefficient, interfacial area, and liquid holdup. This paper aims to evaluate the performance of many correlations to represent the HPC process. An automatic procedure was developed to test a high number of equations, using MATLAB and Aspen Plus software. The best set of correlations was found after a comparison with industrial data. Correlations with errors less than 10% for the entire evaluated operating conditions were calculated for mass transfer coefficient and the interfacial area, as well as for liquid holdup.

Resumo em Inglês:

Diethylene glycol is an extremely toxic substance to humans. Recently, cases of beer contamination in Brazil have raised awareness of the need for developing simple screening methods to evaluate this type of compound. This research developed a liquid-liquid extraction with low-temperature partitioning technique to determine diethylene glycol in beer via gas chromatography. Employing a flame-ionization detector simplifies the method, lowers its cost and therefore, it can be used as screening step to assess the possibility of contamination. A gas chromatograph coupled to a mass spectrometer would be used only for a confirmatory analysis. The optimized method was validated for the main figures of merit, and it proved to be adequate, with good values of recovery rate (94-106%), limit of detection (3.0 mg L-1), and quantification (10.0 mg L-1). Accuracy, in terms of repeatability and intermediate accuracy, showed variation coefficients lower than or equal to 20%. This method was applied to 28 samples of beers marketed in Brazil, and diethylene glycol was found above the limit of detection in three of them (10.7%). These results were confirmed by a gas chromatograph coupled to a mass spectrometer, which showed the reliability of the screening method for determining diethylene glycol in beer samples.

Resumo em Inglês:

The Brazilian regulations for processed coconut water establish the range concentrations of Na and K, being necessary high-throughput analytical methods, as microwave-induced plasma optical emission spectrometry (MIP OES) for quality control. Samples of natural (green and mature) and processed coconut water were treated by acid decomposition assisted by microwave radiation before their MIP OES analysis. Recoveries for Na and K were 103 and 95%, whereas the relative standard deviation (RSDs) were 7.6 and 1.3%, respectively. The limit of detection (LOD) was 1.77 mg kg-1 for K and 2.31 mg kg-1 for Na. Na and K were determined in the ranges of, respectively, 27-490 and 1,600-3,500 mg L-1 in natural samples, whereas in processed samples the ranges were 26-168 and 814-2,054 mg L-1. K-means cluster analysis identified a group of processed samples with compositions similar to green coconut water. All the processed samples were in accordance with the established regulation, except one dehydrated sample for which K content was below the accepted range. Natural coconut water is an excellent source of K in the diet as its daily consumption can supply more than 20% of the recommended daily ingestion of K for adults and 30% for children.