Resumo em Inglês:

In this work, novel nanocomposite beads based on polyvinyl alcohol (PVA) coated polyacrylonitrile (PAN) with encapsulation of TiO2 nanoparticles (PPT) were developed successfully via a novel green synthetic method and its methylene blue (MB) removal ability by adsorption was also investigated. As-prepared nanocomposite beads were characterized by different techniques such as Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). TiO2 nanoparticles were encapsulated into the composite beads to endow the composite beads with photocatalytic ability and enhance its adsorption capacity for MB. Batch experiments with several variables such as TiO2 nanoparticle content, pH of the solution, contact time and initial MB concentration were carried out. The adsorption kinetic study revealed that the MB adsorption process agreed well with pseudo-second order model and showed 3-stage intraparticle diffusion model. The adsorption isotherm study indicated that the MB adsorption process could also be better described by Langmuir isotherm model. According to Langmuir isotherm equation, the maximum adsorption capacity and removal rate for MB was 242.13 mg g-1 and 98.4%, respectively. Moreover, the stability and reusability of as-prepared PPT beads were further explored and results demonstrated that PPT could be reused at least five times with negligible loss of sorption capacity and removal rate. Therefore, PPT is expected to be a potential candidate for effluents treatment.

Resumo em Inglês:

Unexpectedly high uranium concentrations, up to 930 µg L-1, approximately thirty times higher than the World Health Organization (WHO) guidance level, were observed in groundwater samples from the mountainous region near Rio de Janeiro City, the so-called “Região Serrana”, approximately 60 km from the city. This region is characterized by a large number of tourist activities and water-related industries, such as mineral water and breweries that can be impacted by these findings. In addition, the water supplies in small communities of this region are partially or entirely based on groundwater sources. Uranium contamination was observed in 7 of the 16 counties in this region. Based on these data, this study concluded that the probability of obtaining uranium-contaminated groundwater is high in some specific areas of this region. In addition, high 222Rn concentrations were verified, with levels reaching 1570 Bq L-1. Furthermore, a maximum level of 4.6 Bq L-1 210Pb was also measured, which has a WHO guidance level of 0.1 Bq L-1. Based on the present findings, it is suggested that any artesian well deeper than 80 m in this region should be tested for uranium and 222Rn.

Resumo em Inglês:

Self-nanoemulsion drug delivery systems (SNEDDS) represent a potential carrier to improve solubility and bioavailability of health care products. In this sense, copaiba oil (CO) loaded on cosurfactant-free SNEDDS formulations (CO-SNEDDS) were obtained by using phase diagram performed on different concentrations of constituents (oil, surfactant and water). The CO-SNEDDS are composed of 1% (m/m) of oil phase, 20% (m/m) of Tween 80, and 79% (m/m) of double-distilled water. Specifically, varying the oil phase to 1% of CO affords the so-called SNECO system, and 1% of CO blended on a 1:1 ratio with coconut oil or sunflower oil affords, respectively, the SNECO-COO and SNECO-SO derivative systems. CO sample was authenticated by gas chromatography equipped with a flame ionization detector and the CO-SNEDDS samples were characterized by droplet particle size, zeta potential, polarized light microscopy, pH, conductivity, refractive index, rheological and surface tension analyses. According to the antioxidant tests reducing power and hydroxyl inhibiting formation, the findings displayed 47.89 and 72.92% for SNECO, 46.48 and 84.11% for SNECO-COO, and 52.46 and 74.48% for SNECO-SO, respectively. From now on CO-SNEDDS based systems become available as promising targets for novel medicinal investigations and also could be undertaken for the oral administration of poorly water soluble drugs.

Resumo em Inglês:

Volatile organic compounds (VOCs) were isolated from acerola fruits (Malpighia emarginata D.C.), by means of different solid phase microextraction (SPME) fibers. For the extraction, the headspace SPME method was used, identifying the VOCs by gas chromatography (GC) with mass spectrometry (MS). The objective of this work was to evaluate the efficiency of SPME fibers and determine the best conditions for extracting VOCs from acerola fruit. The investigated conditions were: extraction time (20, 30 and 40 min), extraction temperature (25, 45 and 65 ºC) and agitation (0, 50 and 100 rpm). Of the evaluated fibers, polydimethylsiloxane (PDMS)/divinylbenzene (DVB) extracted the highest number of VOCs, most belonging to terpene, carboxylic acids and hydrocarbons. According to the investigated conditions, most compounds were obtained with an extraction time of 20 min, extraction temperature 65 ºC, and no agitation. Compounds cumene, o-xylene, thymol, m-cymene, o-cymene, 2-methyl-1,3-butadiene, anethol, 3-buten-2-one and methyl octadecanoic ester were responsible for the volatile profile of acerola.

Resumo em Inglês:

The present work aimed the study of atmospheric deposition of toxic elements near to a tannery industry by collecting black material deposited on leaf surfaces of cinnamon trees (Cinnamomum zeylanicum). Elements such as As, Ba, Cr, Cu, Fe, Ni, Pb, Sb, V, and Zn were analyzed by inductively coupled plasma mass spectrometry (ICP-MS). For comparison purpose, black particles deposited on the leaf surface of lemon trees (Citrus lemon) collected away from the tannery industry were also analyzed. Results showed that the amount of toxic elements found in the black particles collected near tannery area was significantly higher than the amount of those measured in the comparison site. Enrichment factors (EF) of As and Cr were markedly impacted by anthropogenic emissions, whereas the other elements were moderately/slightly enriched. Cluster analysis (CA) identified the leather industry as the anthropogenic source, while As possibly comes from the wide use of pesticides and herbicides in agricultural practices. The results indicated that emissions from the leather industry and agricultural activities are the main source of pollution in this area.

Resumo em Inglês:

Synthetic herbicides are widely used for weed control in crops. Continuous application of chemicals induces the adaptation of weeds, leading to the development of resistance. Therefore, research for novel synthetic herbicides plays an important role in crop protection and food production. Within this context, it is important to understand the relationship between the structures of a set of compounds endowed with herbicide activity and their biological response. In this work, a quantitative structure-activity relationship (QSAR) study of 34 nostoclide analogues was carried out in order to analyze their ability to inhibit the photosystem-II. Compounds were optimized using the DFT/B3LYP/Def2-TZVPP method. 2D and 3D (Lennard-Jones and electrostatic potential energies) molecular descriptors were calculated at the same theory level. QSAR models showed major importance of electrostatic ligand-acceptor interactions and indicated the presence of aromatic interaction in the benzyl group. A photoelectron transfer via hydrogen-bond was proposed to occur between His215 residue and the carbonyl group.

Resumo em Inglês:

Efficient evaluation of biotoxicity of organics is of vital significance to resource utilization and environmental protection. In this study, toxicity of 110 alcohol compounds to tadpoles of Rana temporaria is adopted as the dependent variable and 1388 physiochemical parameters (features) calculated by PCLIENT are used for representing each compound. A feature selection pipeline with three steps is developed to refine the feature subset: 282 features that significantly correlated with biotoxicity of chemical compounds are preliminarily selected via the maximum information coefficient (MIC); 138 descriptors that have positive contribution to the model’s performance are reserved after a support vector regression (SVR) based backward elimination; 18 descriptors are finally selected via a forward selection process that integrated minimal redundancy maximal relevance (mRMR), MIC and SVR. In terms of feature subsets with different numbers of variables, quantitative structure activity relationship (QSAR) models are built using multiple linear regression (MLR), partial least square regression (PLS) and SVR, respectively. The independent prediction evaluation index, Q2, increases from -74.787, 0.824 and 0.868 to 0.892, 0.878 and 0.940, for the three regression models, respectively. Results suggest that nonlinear feature selection methods involved in MIC and SVR can effectively eliminate irrelevant descriptors. SVR outperforms classical statistical models to QSAR modeling on high-dimensional data containing nonlinear relationship between features. The methods proposed in this study have a potential application in the QSAR research field such as biotoxicity compounds.

Resumo em Inglês:

It was synthesized nine polyoxygenated chalcones with a potential and safe use as antioxidant, antimicrobial and anti-inflammatory therapies. Chalcones obtained by Claisen-Schmidt condensation were studied as antioxidant, inhibitors of human 5-lipoxygenase, antifungal, antibacterial and antibiotic resistance modifiers. Two chalcones with catecholic moieties were able to strongly decrease the minimum inhibitory concentration (MIC) of methicillin against methicillin-resistant Staphylococcus aureus, increase the antiradical activity and significantly inhibit the human 5-lipoxygenase. Only one of these chalcones was active synergistically with methicillin. Chalcones with methoxyl substituents at different positions displayed the best activities against Cryptococcus neoformans. Only one chalcone showed good activity against the plant pathogenic bacteria Pseudomonas syringae whose half maximal inhibitory concentration (IC50) value (2.5 µg mL-1) was similar to that observed with the antibiotic streptomycin (2.9 µg mL-1). These simple chalcones have safe potential uses in antioxidant, antimicrobial and anti-inflammatory therapies.

Resumo em Inglês:

This work reports on oxygen evolution reaction (OER), studied at nickel wire electrode material. Electrocatalytic behavior of non-oxidized and electrooxidized Ni wire samples was evaluated in 0.1 mol dm-3 NaOH solution for the potential range: 1600-2000 mV vs. RHE. The performance of nickel electrodes was examined by alternating current (a.c.) impedance spectroscopy, cyclic voltammetry and Tafel polarization measurements. Electrochemical oxidation of Ni wire radically increased the kinetics of the OER, exhibited through reduced charge-transfer resistance parameter and considerably modified Tafel polarization slopes.

Resumo em Inglês:

In this work, efficient adsorbents for β-lactam antibiotics based on mesoporous iron oxide containing surface [FeOx(OH)y] sites were produced by controlled precipitation of iron hydroxide and thermal treatment at 150, 200, 300 and 450 ºC (150FeOH, 200FeOH, 300FeOH and 450FeOH, respectively). Mössbauer, X-ray diffraction (XRD), thermogravimetry-mass spectrometry (TG-MS), Fourier transform infrared spectroscopy (FTIR), Raman, Brunauer-Emmett-Teller method (BET), scanning electron microscopy (SEM) and elemental analyses showed that the temperature caused a gradual dehydroxylation process with a significant increase of the mesoporous surface area (e.g., 114-142 m2 g-1 with 46-59% mesopores, i.e., 0.04-0.09 cm3 g-1) and approximate compositions of FeO1.06(OH)0.89 for 150FeOH up to FeO1.38(OH)0.26 for 450FeOH. The material 150FeOH showed high adsorption capacities of ca. 42 and 58 mg g-1 for amoxicillin and ceftriaxone, respectively. Experiments assessing the effect of NO3-, Cl-, competitive PO43- adsorption and H2O2 decomposition suggest that the [FeOx(OH)y] surface sites located in the mesopores are involved in the efficient adsorption by complexation of the β-lactam antibiotics.

Resumo em Inglês:

A new and fast method was developed to determine the iodine number of biodiesel samples by capillary zone electrophoresis (CZE). In this procedure, the biodiesel sample reacts with Wijs solution in the presence of a catalyst and all the remaining iodine monochloride is converted to the iodide ion, which is quantified by CZE. Only small amounts of sample and reactant are required and µL level amounts of chloroform and Wijs solution. The reaction time was reduced to 3 min and the total analysis time is less than 15 min. The simplicity and speed of the method can be further enhanced by using single-point calibration. The limits of quantification (LOQ) and determination (LOD) values were better than 0.6 and 0.18 g per 100 g of biodiesel. Instrumental, intraday, and interday precisions were better than 1.13, 1.04 and 6.02% relative standard deviation (RSD). The accuracy was statistically verified by comparison with the standard method EN 14111.

Resumo em Inglês:

Chrysotile:cement roofing sheets were milled with and without K2HPO4. As indicated by X-ray diffraction (XRD), the samples crystallinities were reduced with the increasing milling time. The same tendency was observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), with disaggregation of the chrysotile fiber bundles and formation of non-fibrous micrometric agglomerate particles. After milling for 16 min, most of the phases present in the cement and chrysotile were transformed into amorphous materials, except quartz, in which the structure integrity was preserved, and calcium carbonate, where the particles were reduced to nanometric size. Both milled samples were submitted to release experiments in water, where the characteristics of a potential slow release fertilizer and acid soil conditioner were observed. The process is a viable alternative not only to eliminate the hazard of chrysotile fibers without the need to remove them from the cement matrix, but also as aggregation value to the milled almost amorphous mixture.

Resumo em Inglês:

In this work, a search for antimicrobial agents against multi-drug resistant (MDR) bacteria was undertaken. It involved two natural diterpenes of different basic skeletons, named ent-kaurenoic acid and ent-pimaradienoic acid, that were used as precursors to access 28 semi-synthetic derivatives that were also submitted to biological assays. All 30 substances were assayed against a set of seven clinically isolated MDR bacteria, including three Staphylococcus aureus strains. Results classified both natural compounds as promising bactericidal antimicrobial agents against these MDR bacteria, especially for their performance in time-kill curve assay, improving on the positive control vancomycin. Moreover, di-hydro ent-pimaradienoic acid, obtained as one of the derivatives, also displayed promising minimum inhibitory concentration (MIC) values against the microorganism set, proving optimum activity against S. aureus strains. Thereby, this work also yielded a promising semi-synthetic bacteriostatic antimicrobial agent against MDR S. aureus. Furthermore, the study was carried out with 30 structures in order to verify the veracity and scope of Urzúa’s hypothesis about the structure-activity relationship between diterpenes and antimicrobial action. Our results are 93% in agreement with this hypothesis.

Resumo em Inglês:

Biodiesel synthesis from soybean oil using methanol and alkaline catalysts occurs in the following two consecutive steps: dispersion of methanol in the oil and methanolysis. The effect of the alkaline catalysts NaOCH3, KOCH3, NaOH, and KOH in the dispersion step at 30-60 ºC and under mechanical stirring at 400 rpm was evaluated. The dispersion step accounts for 44.6-73.3% of the total synthesis time and was poorly favored compared to methanolysis due to the increase in temperature. The catalysts decreased the dispersion time, although most of them increased the methanol-oil interfacial tension. K-containing catalysts were more active than their Na analogues due to higher adsorption of K+ in the methanol-oil interface and the higher production of methyl esters (which act as emulsifying agents), which promote a more favorable interfacial tension. The alkaline cation effect was more significant in the dispersion step than in the methanolysis step.

Resumo em Inglês:

Vegetable oil analyses, especially due to the complexity of the oil components, are commonly laborious, requiring several analytical techniques. In this work, electrospray ionization mass spectrometry with direct injection (DIMS), along with 18-crown-6 ether (crown ether) chelating agent and trifluoroacetic acid (TFA), was used to characterize and semi-quantitatively evaluate commercial vegetable oils. As a result, an unprecedented DIMS method of triacylglycerols (TAGs) analysis for semi-quantitative profiling of fatty acids in commercial oils (e.g., soybean, sunflower, corn, oil, canola), without sample derivatization, was developed. The results of the ion abundances related to the analyzed TAGs, with quantitative percentage analyzed by gas chromatography with flame ionization detector (GC-FID), allowed generating correction factors for each oil. DIMS analysis with crown ether/TFA resulted in the elimination of isobaric interferences from sodium and potassium adducts, facilitating the ion assignments, due to the one-ion-per-molecule observation in the mass spectrum. Chemometric analyses by principal component analysis (PCA) and heatmap, to evaluate the ionic profile of the oils, grouped them accordingly to their TAG content. Olive oil was identified as the most different from the other oils. Overall, a semi-quantitative approach to investigate the vegetable oils, reaching low percentage variation for DIMS, with 2 min analyses and 30 min sample preparation, was proposed.

Resumo em Inglês:

In this paper, we report the catalytic cracking of soybean oil for biofuel over γ-Al2O3/CaO composite catalysts. The influence of catalysts, cracking temperature and weight hourly space velocity (WHSV) on the products distribution were investigated. The maximum yield (70.0 wt.%) of biofuel with low acid value (6.7 mg KOH g-1) and oxygen content (5.6%), as well as high calorific value (44.2 MJ kg-1) was achieved over 35 wt.% γ-Al2O3/CaO at 480 ºC and 3.72 h-1. The paper focused on the variation of biofuel composition and cracking pathway caused by γ-Al2O3/CaO composite catalysts via gas chromatography-mass spectrometry (GC-MS) and thermogravimetric (TG) analysis. Calcium oxide would react with fatty acid to yield calcium carboxylates at 300-350 ºC, which were subsequently decomposed into hydrocarbons (57.9 wt.%) and ketones (22.6 wt.%) at 415-510 ºC. As for 35 wt.% γ-Al2O3/CaO, the addition of γ-Al2O3 was beneficial to generate alkenes (38.2 wt.%), arenes (10.6 wt.%) and alcohols (12.3 wt.%) with ketones decreasing (16.5 wt.%) via γ-hydrogen transfer reaction and disproportination.

Resumo em Inglês:

Natural dyes can be used in dye sensitized solar cells (DSSCs) to generate low-cost devices, although with low light harvesting because of energy losses from the recombination process. This study investigates recombination reactions in DSSCs with natural dyes extracted from eggplants, plums, and hibiscus flowers. Titanium dioxide films were coated on a fluorine-doped tin oxide glass conductor substrate by the doctor blading method and impregnated in a dye solution for 24 h. Electrodeposited platinum was used as the cathode, and I3–/I– as the redox couple. The techniques employed were: intensity modulated photovoltage spectroscopy, intensity modulated photocurrent spectroscopy, electrochemical impedance spectroscopy, charge extraction, and cyclic voltammetry. The results show that cells containing plum dye exhibited the best photovoltaic parameters, with high values of gap, charge extraction, and potential, being less resistive to charge transfer with an electron lifetime of 0.51 s, collection time of 8.54 ms, and charge efficiency collection of 0.99.

Resumo em Inglês:

The objective of this study was to explore the extraction and identification of volatile organic compounds (VOCs) present in cagaita fruit (Eugenia dysenterica). Parameters such as type of extraction fiber, agitation, extraction time and extraction temperature were investigated. Initially, the VOCs were extracted using headspace solid-phase microextraction. Then, the compounds were identified using gas chromatography coupled to mass spectrometry. Results revealed the presence of at least 26 different compounds and the polyacrylate (PA) fiber promoted the extraction of a larger number of VOCs. Regarding the PA fiber, the most efficient extraction was achieved using a 50 rpm agitation at 45 ºC for 30 min. The majority were monoterpenes (34.64%) and esters (36.28%). An increase in the extraction temperature promoted the isolation of more VOCs when using carboxen/polydimethylsiloxane (CAR/PDMS) and divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS) fibers. However, these fibers allowed the isolation of a smaller number of VOCs. The extraction time and agitation had no significant influence.

Resumo em Inglês:

Temnadenia odorifera is an endemic species from the Brazilian Atlantic Forest. This study was developed in order to identify the volatile compounds emitted by the living flowers and nectar, to evaluate the temporal pattern of scent emission, and the sugars composition of its nectar. Analyses of the flower scent by dynamic headspace in vivo, of nectar sugar composition and studies on floral biology were performed. Twenty-three volatile compounds were identified in the flowers scent. The total amount of odor emitted by flowers varied significantly throughout anthesis, ranging from 10232.7 ng g-1 (9 to 12 h) to 620.2 ng g-1 (15 to 18 h). 2-Phenylethanol and (E)-cinnamyl alcohol were the major compounds. Concentration ratio between disaccharides and the sum of hexoses ranged from 2.3 to 3.04, which can be correlated to the physiological needs inherent to big bees, the most frequent insects in T. odorifera. Analysis of the chemical composition of T. odorifera flowers provided a broader understanding of the mechanisms responsible for plant-insect interactions.

Resumo em Inglês:

Benzo[a]pyrene (BaP) is often used as a marker of polycyclic aromatic hydrocarbons (PAHs) in beverages. This marker is often quantified by chromatographic methods, which require sample preparations involving the use of reagents, solvents, extraction, pre-concentration, and/or cleanup steps. In this study, a new method for quantification of BaP in cachaças (liquors) that does not use any sample preparation was developed. Interferents in cachaças were overcome using excitation-emission matrices data modeling with parallel factor analysis (PARAFAC). The recoveries ranged from 93.20 to 101.13%, and the relative error of prediction and limit of detection were, respectively, estimated at 2.66% and 2.88 ng mL-1. The proposed method is inexpensive and less time consuming than other approaches described in the literature, uses no reagents, solvents or extraction, has no pre-concentration or cleanup steps, contributing to green analytical chemistry.

Resumo em Inglês:

Two new polyunsaturated 3,4-epoxy-heneicosane derivatives named as epoxy-lobophorene A and epoxy-lobophorene B were isolated from the brown alga Lobophora variegata, in addition to nine known compounds. The structures of the new compounds were elucidated using a combination of 1D/2D nuclear magnetic resonance (NMR) spectroscopy and high-resolution mass spectrometry (HRMS). The isolated compounds were submitted to antiproliferative assays against the human colon cancer cell line HCT-116, human metastatic prostate cancer PC-3M, murine metastatic melanoma B16-F10 and murine fibroblast cell line L929 and also tested as antibacterial. Both 3,4-epoxy lobophorene A and 3,4-epoxy lobophorene B depicted moderate antiproliferative effect against cell lines. None of them showed antibacterial activity.

Resumo em Inglês:

The aim of this study was to investigate impacts of Amazon Forest (AF) fire and conversion to pasture on carbon accumulation in particle size fractions and organic matter (OM) composition of an Acrisol. Soil samples were collected (0.00-2.00 m depth) in three sites: native AF (NAF); AF under natural regeneration for two years after burning (BAF); 23-years old Brachiaria pasture after AF burning (BRA). Assuming NAF area as reference, BAF and BRA areas showed negative carbon balance when carbon emitted to the atmosphere at AF burning is taken into account. Soil OM aromaticity and hydrophobicity, assessed via 13C nuclear magnetic resonance, in BRA and BAF were similar to that in NAF. Fire and post-fire land use altered the carbon distribution in sand, silt and clay along the soil profile and seem to have affected organo-mineral and OM self-assemblage interactions, since the relation between total soil carbon and carbon in clay was asymptotic in BAF and linear in NAF and BRA.