Resumo em Inglês:

Vochysia divergens Pohl, known as "Cambara" in Brazil, is an invasive species that is expanding throughout Pantanal in Brazil, to form mono-dominant communities. This expansion is affecting the agricultural areas that support the typical seasonal flood and drought conditions of this biome. This article describes the development and validation of an HPLC-DAD analytical method to quantify 5-methoxyflavones in methanolic extracts of greenhouse-grown V. divergens associated with one of two endophytic fungal species Zopfiella tetraspora (Zt) or Melanconiella elegans (Me) and later subjected to water stress. The developed method gave good validation parameters and was successfully applied to quantify the flavones 3',5-dimethoxy luteolin-7-O-β-glucopyranoside (1), 5-methoxy luteolin (2), and 3',5-dimethoxy luteolin (3) in the target extracts. Inoculation of the plant with Zt decreased the concentration of flavone 1 in the extract by 2.69-fold as compared to the control. Inoculation of the plant with Zt or Me did not significantly alter the contents of flavones 2 and 3 in the extracts as compared to the control. Therefore, the aerial parts of germinated V. divergens plants inoculated with either Zt or Me responded differently in terms of the production of flavones. These results can cast light on the symbiosis between fungal microorganisms and V. divergens, which most likely influences the response of V. divergens to changes in the availability of water in Pantanal.

Resumo em Inglês:

The structures and molecular interactions of (R)nN-CO2 complexes of amines and CO2 in the gas phase were computationally studied by using ab-initio methods and quantum theory of atoms in molecules (QTAIM). The analysis of the electrostatic potential showed that the interaction N∙∙∙C present in this type of aggregates is favored by the potential difference between the N and C atoms. On the other hand, it was observed the interaction energy is being more exergonic in molecular aggregates having highly substituted amino groups and cyclic structure; in addition, the geometric deformation of CO2 and other additional molecular interactions facilitate the process of complexation of this gas. The QTAIM analysis showed that the interaction N∙∙∙C has an electrostatic character and its strength increases with the substitution of the amino group.

Resumo em Inglês:

Toca Exú do Jurubeba is part of a set of archaeological sites located in the Serra da Capivara National Park (Piauí, Brazil), a region of great world interest due to its archaeological potential, especially rock art. However, rock art is constantly threatened by both natural and anthropic factors. Among the natural salts efflorescences that are deposited on the painted graphics often even concealing them. The present study consisted of the spectroscopic analysis of different saline efflorescence samples of the Serra da Capivara National Park, using examination techniques (optical microscopy and Scanning Electron Microscopy) and analysis (Fourier Transform Infrared and Laser Induced Breakdown Spectroscopy). The analysis allowed to identify at least four different compositions of the samples as a mixture of hydrated calcium oxalate (CaC2O4 H2O) with kaolinite (Al2SiO3(OH)4), gypsum (CaSO4 2H2O), tetrahydrate calcium nitrate (Ca(NO3)2 4H2O) and aluminosilicates in the state of fossilization. The obtained results open the way for the conservation of rock art, initially in the archaeological site under study and can serve as basis for other interventions that may be developed in the region.

Resumo em Inglês:

The use of a palladium film electrode (PdFE) as an alternative electrode for the determination of thallium (Tl+) and lead (Pb2+) in water samples by anodic stripping voltammetry is proposed. Preliminary studies of the influence of the substrate were performed on the electrochemical behavior of PdFE prepared ex situ. Using a silver solid amalgam electrode as substrate (AgSAE), the effect of several parameters such as potential and deposition time, composition and pH of supporting electrolyte on the analytical response of PdFE for Tl+ by differential pulse anodic stripping voltammetry (DPASV) was initially investigated. Under best experimental conditions of deposition potential of −1.2 V and deposition time of 300s the analytical curve was linear in the Tl+ concentration from 3.0 to 100.0 µg L−1 with a relative standard deviation (RSD) <2.0%. The limit of detection (LOD) and limit of quantification (LOQ) were 0.89 µg L−1 and 2.96 µg L−1, respectively. The PdFE was successfully applied for the determination of Tl+ in water samples. Moreover, this electrode showed promising as a sensor for the simultaneous determination of Tl+ and Pb2+ and as a suitable alternative to the mercury electrode.

Resumo em Inglês:

The synthesis, characterization and antimicrobial activity of novel vanadium (IV) complex derived of amide natural piplartine is reported. The minimum inhibitory concentrations (MIC) of complex, piplartine and vanadyl sulphate used in the synthesis were determined against six bacteria and one fungus. The complex exhibited good activity with minimal inhibitory concentration values ranging from 156.2 to 625 µg mL-1, it was observed the lowest value for the Escherichia coli bacteria with MIC 156.2 µg mL-1 and Microsporum gypseum fungus with MIC 312.5 µg/mL. In overall, the complex showed better antimicrobial activity than the piplartine. Additionally, the V-PIP complex was completely soluble in water, on the contrary of the piplartine free; which means that the proposal complex consists in a potential candidate to drug.

Resumo em Inglês:

Lactobionic acid and its salts are substances that have several applications in the pharmaceutical area. These products were obtained by bioconversion through the enzymatic complex glucose-fructose-oxidoreductase (GFOR)/gluconolactonase (GL) present in calcium alginate immobilized cells of Zymomonas mobilis. In the reactions catalyzed by this enzyme system, the medium pH must be controlled at slightly acid values. For this purpose, NaOH, KOH, or Ca(OH)2 were used, and as a result, the respective salts were formed. The kinetic study on the formation of sodium, potassium and calcium lactobionates was followed by the steps of purification and characterization aiming the potential use of these compounds in the pharmaceutical area. In the assays for the bioproduction of sodium, potassium or calcium lactobionates, yields of 74, 77 and 84% were obtained, respectively. In the salts purification step, purity levels of approximately 95% were achieved. The structural identities of the lactobionate salts were determined by high resolution mass spectrometry, in addition to the 13C and 1H NMR analysis. The characterization demonstrates the selectivity of the enzymatic reaction of GFOR/GL of Z. mobilis, in the production of lactobionic acid and its salts.

Resumo em Inglês:

This paper describes the optimization of a sample preparation method using response surface methodology for Al, Cd, Cu, Fe, Mg, Mn, Mo, Na, Ni and Ti determinations in samples of rice husk and rice husk ash by MIP OES. Sample preparation was performed using a reflux system adapted to the digestion tubes. This system allowed the decomposition of the samples without the necessity of replacement of the acids during this step without any loss of volatile elements. The decompositions were performed with 3.6 mL of HNO3 and 1.4 mL of H2SO4 for 205 min in a digester block at 225 ºC. The detection limit for determination of respective analytes in both samples were satisfactory. The RSDs for the analytes were less than 10%. Moreover, the accuracy of the method can be verified by recovery tests, whose values ranged from 82 to 115% for husk samples and 82 to 120% for ashes. The proposed method was presented as a simple, safe and low cost procedure being suitable for sample preparation and subsequent determination of metals by MIP OES.

Resumo em Inglês:

Hexagonal boron nitride (h-BN), graphite analogous structure, has many interesting applications due to its excellent thermal, electrical and mechanical properties. In this study, different routes of liquid exfoliation using solvent and ultrasound were used to obtain two-dimensional (2D) nanosheets of h-BN. The efficiency of the exfoliative routes was evaluated by Transmission electron microscopy (TEM) and UV-Vis spectroscopy. Results demonstrated that the technique was effective in the exfoliation of h-BN bulk and that the solvent's choice, considering an optimum surface tension of the solvent-solute system, and the rotation of the centrifugation in the selection of the exfoliated nanosheets, are crucial for the performance of the technique. The most promising exfoliation route has been found to be the dispersion of h-BN in solvent mixture (20% IPA in water) for 3 h on ultrasound, followed by centrifugation at 1500 or 3000 rpm.

Resumo em Inglês:

In this paper, a computational methodology based on Artificial Neural Networks (ANN) was developed to estimate the index of PM10 and PM2.5 concentration in air of San Francisco de Campeche city. A three layer ANN architecture was trained using an experimental database composed by days of the week, time of day, ambient temperature, atmospheric pressure, wind speed, wind direction, relative humidity, and solar radiation. The best ANN architecture, composed by 30 neurons in hidden layer, was obtained using the Levenberg-Marquardt (LM) optimization algorithm, logarithmic sigmoid and linear transfer functions. Model results generate predictions with a determination coefficient of 93.01% and 90.10% for PM2.5 and PM10, respectively. The proposed methodology can be implemented in several studies as public health, environmental studies, urban development, and degradation of historical monuments.

Resumo em Inglês:

Chemical investigation of Croton gratissimus led to the isolation of fourteen compounds, and their structures were identified to be caryophyllene oxide (1), 1β-methoxycaryolan-9β-ol (2), kaur-16-en-19-oic acid (3), cis-ozic acid (4), spathulenol (5), lupeol (6), 7δ-methoxyopposit-4(15)-en-1β-ol (7), germacra-4(15),5,10(14)-trien-1β-ol (8), β-sitosterol (9), ent-kaur-16-en-18-ol (10), 15-methoxy-neo-clerodan-3,13-dien-16,15-olide-18-oic acid (11), 6α-methoxyeudesm-4(15)-en-1β-ol (12), sucrose (13) and N-methyl-trans-4-hydroxy-L-proline (14) on the basis of 1D and 2D-NMR spectra. This is the first report on the occurrence of compounds (2), (4), (7), (9-12, 14) in the genus Croton.

Resumo em Inglês:

The extraction of kahweol and cafestol involves saponification reaction. This step is important for the efficiency of the extraction as the diterpenes are susceptible to structural changes during hydrolysis. The microwave-assisted saponification has been successfully used in different matrices, but there is no previous report of the use of this technique in the saponification of diterpenes. Therefore, the effect of microwave-assisted saponification on the extraction of kahweol and cafestol in roasted coffee was evaluated. A 32 factorial experimental design was used in order to evaluate the effect of temperature (70, 80, and 90 ºC) and reaction time (4, 8, and 12 min). The quantification of diterpenes was performed by high-performance liquid chromatography and the results were compared to with those obtained by a method, which uses thermostatic bath for saponification. Temperature and time had a significant effect (p < 0.05) on diterpenes levels. For simultaneous saponification of kahweol and cafestol, the optimal reaction conditions were 80 ºC / 12 min. The use of microwave-assisted procedure lead to lower yields of kahweol (24%) and cafestol (35%) compared to reference method. However a significant reduction of reaction time (80%) was achieved, and the procedure also has the advantage of controlled process conditions and the possibility of extended scale.

Resumo em Inglês:

Alzheimer's disease is an irreversible, degenerative and age-related disease which is growing more and more with the increase in life expectancy. Kaurane diterpenes are a class of natural products available in large amounts in nature and isolated from plants grown worldwide. In the present work¸ twenty-seven kaurane diterpenes of natural origin and some readily available derivatives were assayed for acetylcholinesterase inhibition and the structure-activity relationship was analyzed. The kaurenoic acid derivatives screened showed to be promising inhibitors of AChE, which could provide new leads for drugs to fight Alzheimer's disease symptoms. Among them, eleven compounds showed activities comparable or higher than the positive control galantamine. Existence of an allylic hydroxyl group showed to be an important structural feature for AChE inhibition. In addition, presence of free hydroxyl groups at C-17 and C-19, furnished a diol especially active, able to completely inhibit AChE.

Resumo em Inglês:

The aim of this study was to develop and characterize a Brazil nut oil microemulsion system and determine the effect of this microemulsion on the superoxide release in human phagocytes. The microemulsion was formulated using distilled water, Brazil nut as the oily phase, Sorbitan monooleate, Polysorbate 80, and butan-1-ol. Hydrophile-lipophile balance of Brazil nut oil was determined, pseudoternary diagrams were prepared, and microemulsion diagram regions were preselected. Preliminary and accelerated stability tests, rheological characterization and dynamic light scattering were performed. The immunomodulatory effect of the microemulsion on the interactions with leukocytes was determined by superoxide release. The developed formulations were classified as oil-in-water, showed a Newtonian profile, with linear viscosity and droplet sizes of 46.9; 66.5 and 34.3 nm. When we assessed the interaction of the microemulsion of Brazil nut oil with phagocytes, we observed an increase in superoxide release. Our findings indicate that the developed formulation improved the immunomodulatory activity of the Brazil nut oil, proving to be a natural product option for future applications, in particular for infectious diseases.

Resumo em Inglês:

The biosynthesis of amylase and collagenase, produced by A. acidocaldarius and A. sendaiensis respectively, were studied, and different matrices evaluated for the microorganisms immobilization and enzymes production optimization, such as loofa sponge, alginate-sponge and alginate, followed by concentration through ultrafiltration. Using a wheat bran substrate, the amylase enzyme displayed enzymatic activity of 0.45 U mL-1 and optimum temperature and pH conditions of 75 °C and pH 3.0, respectively. Thermal stability was in the range of 55 to 60 °C. The apparent Km and Vmax were 3.2 mg mL-1 and 0.5 U mL-1, respectively. The production of collagenase by A. sendaiensis was carried out with potato dextrose broth substrate and the activity obtained was 7.2 U mL-1. For amylase, the best results were obtained from immobilization in loofa sponge and the use of ultrafiltration (0.67 U mL-1) and for the collagenase extract, from the free biomass and ultrafiltration (13.6 U mL-1). The use of an ultrafiltration system enabled an average increase of 54% in the activity of both enzymes. Therefore, Alicyclobacillus are capable of producing enzymes of industrial interest, with the possibility of economically viable application of the substrate, and the use of immobilization and ultrafiltration produced positive results.

Resumo em Inglês:

In this work a series of 2-(2- pyridyl)quinolines were prepared via a Povarov reaction between anilines, 2-pyridinocarbadehyde and ethyl vinyl ether under microwaves heating conditions. The optimized conditions herein reported allowed the preparation of several pyridylquinolines in yields in the range of 30-83%, some of them not previously accessible by this multicomponent process. The reported methodology has advantage over previous report due to its larger scope and short reaction time (2 hours). All quinolines obtained were assayed against five species of clinically important yeasts Candida sp and against Cryptococcus neoformans. Some of them possessed a broad spectrum of action including 2-(2-pyridyl)quinoline (20) and 6,8-dimethoxy-2-(pyridin-2-yl)quinolone (22) that were highly effective in inhibiting Candida species (IC50 < 1.95 µg/mL against C. tropicalis and C. krusei). Some compounds were more potent than commercial drugs Nistatin and Miconazole.

Resumo em Inglês:

Spectroscopy associated with chemometrics is a non-destructive method of the samples for the prediction of phenolic compounds. The objective of the work was to apply the near infrared spectroscopy (NIR) technique for the prediction of phenolic compounds and flavonoids in aerial part samples of cover crops plants Raphanus sativus L., Secale cereale L. and Avena strigosa L. Samples were collected at 60, 80 and 100 days after sowing (DAS) of the plants and, after lodging (DAA), at 15 and 30 days, in an experiment implanted in the field, in the city of Ituporanga, Santa Catarina. The samples were homogenized, identified, transported on dry ice, lyophilized, crushed, sieved and stored at -20 °C for analysis. For the calibration, 84 samples were used and for the validation 10 samples. The combination of NIR spectroscopy and multivariate analysis by partial least squares regression allowed the development of prediction models of phenolics and flavonoids with associated errors averaging 10%. NIR spectroscopy is recommended for the development of calibration models because it allows to non-destructive infer phenolic and total flavonoid contents, with high analytical frequency, without the use of reagents and other inputs required by the reference method, with results very close to those obtained in the laboratory.

Resumo em Inglês:

The second generation (2G) ethanol obtained from lignocellulosic biomass has been considered as a potential alternative source of energy for the transportation sector. However, the technologies to convert lignocellulose into fermentable sugars still face several challenges. One of the major challenges of this process is related to the cost of the cellulolytic enzymes. Thus, the development of bioprocesses for enzyme production and strategies to increase the final yield of the enzymatic hydrolysis reactions are required to ensure the economic feasibility of the biomass conversion process. In this review, it is discussed the progress related to fungal enzyme technology over the past few years with major emphasis on the biocatalysts needed for cellulose degradation as well as on cultivation strategies for the production of enzymes on-site. The potential of applying secretome analysis as a tool for the characterization of the enzymatic complexes and some limitations on the use of enzymatic cocktails in the saccharification step, such as the unproductive adsorption of enzymes onto lignin are also discussed in light of the recent literature.

Resumo em Inglês:

Emerging contaminants occur in parts per trillion or less in aquatic matrices. The effects related to the exposure of aquatic biota and human to them have been identified for different compounds. The knowledge about the concentrations of the exposure is the first step to perform risk assessments. The present work describes a literature review about occurrence in Brazilian aquatic matrices, and a discussion about biological effects, legislation and analytical aspects involving the presence of emerging compounds. The review includes 58 papers published between 1997 and 2016, considering the occurrence of personal care and pharmaceutical compounds, illicit drugs, hormones, pesticides and some other endocrine disruptors compounds in the matrices sewage, surface, ground and drinking waters. The concentrations varied from ng L-1 to µg L-1, depending on the region and the compound. However, the contamination scenario was aggravated by the combination of poor sanitation status - such as low investment in sewage treatment plants, which led to an expressive contamination of the receiving waters with sewage - and the current goods consumption level, which is similar to that of developed countries. These data provide a good insight into the particular levels of contamination and can be used both for further researches and decision making in the regulation area of public policy.

Resumo em Inglês:

Biodiesel purity expressed as fatty esters content is one of its most important quality parameters. Although several instrumental methods have been employed, gas chromatography with internal standard calibration has been the most used. Biodiesel is a very complex matrix, therefore finding a suitable internal standard (IS) is not straightforward. EN14103:2003 standard established methyl heptadecanoate (C17:0) as IS. Since this fatty ester is naturally present in some biodiesel feedstock as tallow, that standard was reviewed in 2011, and methyl nonadecanoate (C19:0) became the new IS. In turn, C19:0 produces a peak on the chromatogram that is difficult to resolve from methyl linoeate (C18:2) and metyl linolenate (C18:3) ones. In this paper, a GC-FID method for the determination of the esters content in methyl and ethyl biodiesel from canola and soy oils, using hexadecyl acetate as a new internal standard was validated. EN14103:2003 was used as reference method. Method selectivity, accuracy (t student parameter < 2.18 from both methods), repeatability (0.1 - 0.4%), intermediate precision (0.2 - 1.8%), and robustness (0.1 - 1.6%) were investigated and considered appropriate for the scope.

Resumo em Inglês:

In this work we describe a methodology to obtain phosphor screens used in various applications to produce images or patterns such as detectors and microscopes. The main advantages of these screens are the particle free and self-heating properties that allows it to be used in controlled environments minimizing the adsorbed gases in the surface of the screen. A polyvinyl alcohol deposited on top of the phosphor layer acts as an adhesive layer preventing the removal of phosphor particles from the screen surface that could result in measurement environment contamination. The tin oxide layer has a high melting point enabling the self-heating. These characteristics on screens are important for ultra-high vacuum environment and to study carbon nanotube emission patterns through field emission microscopy (FEM).

Resumo em Inglês:

This paper addresses a didactic activity based on computer-supported collaborative learning (CSCL) principles applied to a scientific communication course offered to undergraduate chemistry students. We investigated the dynamics of interactions among the students within the groups focusing on skills of conversation described in the Collaborative Learning Model developed by Soller et al. In a virtual learning environment named eduqui.info students solved investigative case studies related to environmental pollution caused by plastic and oil, replacement of aviation gasoline by ethanol and replacement of trans fat found in foods. The messages posted on eduqui.info Forum were analyzed for the identification of the students' collaboration effectiveness. The major subskills related to Collaborative Learning Model found in the students' messages were inform, argue and request. Activities like the one addressed in this study can help undergraduate chemistry students to learn and apply core scientific concepts and skills.

Resumo em Inglês:

Volhard method is extensively employed in the teaching laboratories of classical quantitative analysis to chloride determination and is based on the reaction of Ag+ with Cl- and Ag+ residual titration with SCN-. Its drawback is that SCN- reacts with the AgCl(s) initially formed. Nitrobenzene is used to avoid this stripping, but it is toxic to the environment and causes problems in final disposal. This work proposed the use of soybean oil as an alternative to nitrobenzene. The traditional and modified methods were applied in the standardization of 0.05 mol L-1 KSCN solution employing 0.05000 mol L-1 NaCl standard and the proposed modification did not affect the results obtained (α = 0.05). No significant differences were observed in the variances and NaCl recovery percentage in the titration of aliquots of 5.00 to 15.00 mL of solution of this salt. The recovery percentages obtained with soybean oil on the titration of synthetic 0.07000 mol L-1 NaCl samples diluted 1:1 to 1:100 were equivalent and even better than with nitrobenzene. The chloride determination in samples of saline, whey cheese, sea water and olive brine obtained by the modified method was satisfactory when compared to the official method with relative errors below 3%.