Resumo em Inglês:

Studies often neglect the different trends between enantiomers in soil chiral contaminants. In the present study, paclobutrazol was chosen as the target analyte and the selective degradation patterns of this chiral pesticide were investigated in soils. After 14 days of culture, the degradation kinetics results demonstrated the degradation process of the two enantiomers conforms to first-order degradation kinetics equation, and the degradation rates were significantly different (paired t-test, P < 0.05). The degradation rate of (2S,3S)-paclobutrazol (S-paclobutrazol) was higher than that of (2R,3R)-paclobutrazol (R-paclobutrazol), with the concentration decrease of 42.6 and 28.7%, respectively. Meanwhile, the enantiomer fraction (EF) was 0.43 at final sampling point, and the half-life (t1/2) of S-paclobutrazol and R-paclobutrazol were 17.3 and 28.9 days, which demonstrated significant enantioselective degradation. Results from this study served to enhance our understanding about the enantioselective degradation behaviors of chiral pesticides, which provided some scientific basis for the potential risk assessment of chiral pesticides in the environment.

Resumo em Inglês:

This paper reports a method for simultaneous determination of H2, O2, N2, CO, CO2, CH4, C2H2, C2H4, C2H6, C3H4 (propadiene and propyne), C3H6, C3H8 and C4H10 (n-butane and isobutane) by gas chromatography using thermal conductivity and flame ionization detectors. A single porous layer open tubular column (0.53 mm internal diameter ? 30 m length ? 30 µm thick) was applied and no catalytic converter was needed to convert CO and CO2 into CH4 to enable identification by a flame ionization detector. The most appropriate chromatographic conditions were defined for the method and it was validated according to the recommendations of the National Health Surveillance Agency and the National Institute of Metrology, Standardization and Industrial Quality. Chromatographic conditions defined for the target gases presented satisfactory linearity (r > 0.99), and limits of detection ranged between 0.0916 and 2.75 ppm. High accuracy (98-101%) obtained for the gas chromatography/thermal conductivity detector/flame ionization detector method associated to low relative standard deviation (?λτ; 2%) confirmed its applicability in routine quantification of target gases formed during the pyrolysis of municipal refuse-derived fuel.

Resumo em Inglês:

CdTe quantum dots (QD-CdTe) functionalized with mercaptosuccinic acid (MSA) were synthesized in an aqueous medium, varying synthesis time from 0.5 to 4 h. The nanoprobe were characterized by a direct relationship between synthesis time and QD size (2.61-3.04 nm). The QD-CdTe-MSA interacted with protamine (PT), a cationic protein, forming a bioconjugate, thus quenching the photoluminescence intensity and generating an on-off system. The nanoprobe produced at a synthesis time of 1 h (QD-CdTe1) presented PT’s best sensitivity in a succinate buffer (pH = 5). Under the optimized conditions, the proposed method presented a linear range of 0.05-0.5 mg L-1 (10-100 nM), limit of detection (LOD) 0.01 mg L-1 (2 nM), and relative standard deviation (RSD) ≤ 2.01% (n = 10). The interaction of the nanoprobe and PT led to aggregation due to a bioconjugate formation. The systems’ hydrodynamic radius varied from 4.31 nm (QD-CdTe1) to 30.50 nm for the bioconjugate (QD-CdTe1-PT). The method was sensitive to variation in ionic strength and based on thermodynamic parameters; it was demonstrated that the interaction mechanism occurred preferentially through electrostatic forces. Finally, the method proved to be fast, sensitive, and viable for quantifying PT in drugs and synthetic urine samples with recoveries above 95%.

Resumo em Inglês:

Selecting a polymer depends on its characteristics, the properties of the drug and of the remaining ingredients in the formulation. The drug, when incorporated into a polymeric matrix, can show several advantages when compared with its conventional form. In this context, this work describes the preparation and characterization of polyethylene glycol (PEG 4000) and its derivative particles loaded with benznidazole, as well as evaluates their trypanocidal activity. In this work, reactions to modify the PEG 4000 polymer and the subsequent incorporation of the benznidazole were made. The nuclear magnetic resonance (NMR) analysis confirmed the efficiency in modifying the PEG chains. The morphology of polymeric films was observed by atomic force microscopy (AFM) and showed considerable changes on the film organization. The acetylation of PEG favored the stability of the system and an increase in the zeta potential from ?14.83 to ?25.54 mV was observed. Although encapsulation efficiency values between 30.14 and 39.48% were found, the enhanced benznidazole dissolution profile by microparticles enables the use of lower drug concentrations. This fact can be proven by the increased trypanocidal effect of benznidazole when encapsulated in BP3 microparticles. Finally, the high selectivity of the formulations for trypanocidal action guarantees their safety as an alternative for the treatment of the Chagas disease.

Resumo em Inglês:

In the brain of patients with chronic Alzheimer’s disease (AD), the butyrylcholinesterase (BuChE) levels rise while the acetylcholinesterase (AChE) levels decrease. Therefore, development of new selective BuChE inhibitors is of vital importance. Here we present a series of bis(n)-lophine analogues, where two lophine derivatives are connected by a methylene chain. The bis(n)-lophine analogues were synthesized through one-pot four component reaction between pyridinecarboxaldehydes, 1,n-alkanediamines, benzil, and ammonium acetate. The reactions were performed in a microwave reactor in one step for symmetrical bis(n)-lophines, and in two steps for unsymmetrical bis(n)-lophines. The compounds are strongly selective to BuChE, since none of them inhibit AChE. All the compounds, except 7a, 7b and 7c, displayed potent inhibitory activity against BuChE at a micromolar and sub-micromolar range (half maximal inhibitory concentration (IC50) 32.25-0.03 µM). The enzyme kinetic and docking studies suggests that the inhibitor act as a dual binding site inhibitor, binding into the bottom of the gorge and in the peripheral anionic site (PAS) of BuChE cavity. Furthermore, in vitro studies showed that compounds 5b and 12b had no cytotoxic effects in kidney Vero, hepatic HepG2 and C6 astroglial cell lines.

Resumo em Inglês:

It is known that the reactivity of the nanocatalytic systems is related to the particle size and shape and also to the features of the capping agents on the nanostructures. In this study, gold nanorods (AuNRs) were synthesized by the seed-mediated method using different tetra-alkylammonium bromide salts as capping agents, that are, cetyltrimethylammonium (CTABr), N,N-dimethyl-N-cetyl-N-(2-hydroxyethyl)ammonium (HEA16Br), and N,N-dimethyl-N-cetyl-N-(2-hydroxypropyl)ammonium (HPA16Br), and used as catalyst for the chemical reduction of p-nitrophenol (PNP) in the presence of NaBH4. The catalytic systems were characterized by ultraviolet-visible (UV-Vis) absorption spectroscopy and transmission electron microscopy (TEM). The effect of the ammonium bromide-based capping agent on the catalytic activity of AuNRs was evaluated by performing the chemical reduction of p-nitrophenol in the presence of excess NaBH4 in aqueous medium. Under the reaction conditions employed, the catalytic systems displayed detectable subtle differences in terms of induction times and apparent activation energy (Ea) values. These results show that slight changes carried out in the chemical structure of the capping agent are able to imprint even slightly modification of the kinetic parameter of the catalytic reaction.

Resumo em Inglês:

Hierarchical ZSM-5 zeolites were prepared by alkali treatment (desilication) at two temperatures, two reaction times, and two NaOH concentrations. A 23 factorial design was used to study the effect of these variables on the crystallinity, microporosity, and mesoporosity of the zeolite due to the desilication treatment. The factorial design analysis showed that the temperature, reaction time and NaOH concentration and the second order interaction between temperature and time have statistically significant effect on the micropore volume. On mesopore volumes (Vmeso) and areas (Smeso), the reaction time and NaOH concentration factors have statistically significant effects. In the case of mesopore volumes, the second order reaction time and NaOH concentration interaction factor are also significant. On the other hand, only the alkali concentration affected, negatively, the relative crystallinity. Two hierarchical ZSM-5 zeolites with the highest relative crystallinity and mesoporosity were selected and further characterized by inductively coupled plasma (ICP) analysis, 29Si nuclear magnetic resonance (NMR), 27Al NMR, Fourier transform infrared (FTIR) spectroscopy in the OH stretch region and pyridine adsorbed FTIR spectroscopy. NMR and FTIR results showed that the alkali treatment selectively removed silica from the zeolite framework, decreasing the SAR (silica-to-alumina ratio) values, while decreasing Brønsted acid site concentrations and increasing Lewis acid sites concentrations.

Resumo em Inglês:

The search for new biomaterials has increased continuously in recent years and, in this context, the application of polypyrrole (PPy) as a promising material for this function has been reported as a result of positive responses, such as bioactivity and biocompatibility. In this study, PPy was obtained through modifications/adaptations made in methodologies of previous papers, which focused mainly on conductive properties. The use of additives in the synthesis significantly improves the application in the biomedical area, which depends directly on a diversity of structural and morphological parameters. Here, physicochemical characterization was helpful to determine PPy structures and morphologies of the resulting samples. The addition of phytic acid (PA) and methyl orange (MO) directly influenced not only the particle morphology and size, but also the antibacterial activity and cytotoxicity. The results of antibacterial activity against Staphylococcus aureus and Escherichia coli as well as the negligible cytotoxicity of PPy obtained here indicate a wide applicability of the materials in wound dressing and tissue engineering.

Resumo em Inglês:

The sol-gel technique has drawn considerable attention in the area of biomolecules immobilization by virtue of its intrinsic properties including chemical inertness, thermal stability, and good biocompatibility. The present work reports the development of a bio-sensing methodology which involves the immobilization of horseradish peroxidase enzyme (HRP) on pencil graphite electrode (PGE) using TiO2 sol-gel and its application for 5-aminosalicylic acid (5-ASA) determination in pharmaceutical formulations. TiO2 sol-gel film was deposited on the PGE surface by dip coating, and the HRP enzyme was immobilized on the film by adsorption and cross-linked binding using glutaraldehyde. The analytical performance of the methodology was investigated through amperometric measurements at -0.08 V in the presence of 5-ASA (electron mediator) and hydrogen peroxide (substrate). The biosensor was successfully applied for 5-ASA determination, where limits of detection and quantification of 3.3 and 10.0 µmol L -1, respectively, were obtained. The application of the methodology for 5-ASA determination in pharmaceutical formulations led to satisfactory recovery rates ranging from 80 to 98%. The biosensor developed in this work is simple, inexpensive and has the potential to be applied for the determination of other pharmaceutical compounds, which also act as electron mediators in the catalytic cycle of HRP.

Resumo em Inglês:

This work deals on the preparation of silicon oxycarbide (SiOC) and silicon boron oxycarbide (SiBOC) ceramics from pyrolysis involving alkoxysilanes with different organic groups. Boron content, organic substituent and annealing time were evaluated on crystallization and composition of resulting ceramics. B-free precursors composed of methyltriethoxysilane (MTES), phenyltriethoxysilane (PTES) and vinyltrimethoxysilane (VTMS) were obtained by the sol-gel method, whilst B-containing precursors were prepared by adding to each alkoxysilane a proper amount of boric acid resulting in B/Si atomic ratios of 0.1 and 0.5. Precursors were pyrolyzed at 1500 ºC for 1 and 3 h to produce respective SiOC and SiBOC ceramics. X-ray diffraction (XRD) patterns revealed enhanced SiC phase crystallization for PTES-derived ceramics, followed by those containing vinyl and methyl groups, which was also confirmed by X-ray photoelectron spectroscopy (XPS) from percentages of SiºC and Si?O bonds. Csp2 and Csp3 amounts varied among ceramics, indicating direct influence of organic substituent on conductive carbon phase development. Boron addition induced the growth of SiC crystallites, having more evident effect in matrices with higher proportions of amorphous fraction and lower residual carbon amounts. Organic group nature, boron content and annealing time played an important role for production and evolution of SiC and C phases into ceramics.

Resumo em Inglês:

Expensive and complex methodologies are available to determine the ethanol concentration in alcohol gel samples. The aim of this article was to demonstrate that alcoholmeter could be used as an alternative method to determine ethanol in gel formulations. Alcohol gel samples were produced using: hydroxypropylmethylcellulose (HPMC), hydroxyethylcellulose (HEC) and Carbopol 940© (CBP). A factorial design was performed to evaluate the interaction between the ethanol concentration, glycerin and polymer contents in the samples in the recovery data of the ethanol content. Rheological analyses were also performed to identify the limiting factors to ethanol quantification. All the results were compared to high resolution magic angle spinning nuclear magnetic resonance (HR-MAS NMR) as a reference methodology. The results demonstrated that the alcoholmeter could be used to determine alcohol concentration, moreover the level of polymer HEC or HPMC, glycerin and ethanol has no effect in the determination. Yield stress, and not viscosity or flow index, appeared as the limiting factor to the use of alcoholmeter in non-acidified CBP samples. Acidification appears to be mandatory to determination of ethanol concentration in CBP samples. It was possible to achieve an inexpensive, handy and fast methodology to quantify alcohol in gelled samples, in the range of concentrations used in this article.

Resumo em Inglês:

The wastewater that originates from the widespread usage of synthetic dyes in the industry have become a severe environmental problem. Several efforts have been made to develop new types of treatment which are capable of performing the degradation of the dyes from the environment. Within this scope, much attention has been drawn to enzymatic approaches, mainly the ones applying oxidative enzymes, such as peroxidases. A recently discovered superfamily of peroxidases, the so called dye-decolorizing peroxidases (DyPs) is a promising alternative to further improve the efficiency of these processes. In this work, two of these peroxidases (Saccharomonospora viridis (SviDyP) and Thermobifida fusca (TfuDyp)) were tested together with twelve different reactive dyes in order to evaluate the efficiency of degradation and decolorization, leading to good results. When applying the SviDyP enzyme in experiments carried out for 12 h in pH 3, the degradation efficiencies were above 80% for some dyes. The biodegradation efficiency data and cyclic voltammograms were recorded to obtain the redox potential of the chosen dyes and enzymes. In addition, an electrochemical biosensor was used to gauge the genotoxicity of the generated bioproducts. This analysis showed that bioproducts from dye degradation mostly present a lower degree of genotoxicity when compared to the control reactions.

Resumo em Inglês:

Reduced graphene oxide/ruthenium oxide hexacyanoferrate (rGO/RuOHCF) modified electrode showed synergic activity between the materials attested by the increase of electrochemical current and stability. The preparation of the nanocomposite was made by a simple two-step electrochemical approach. The material structure was characterized by spectroscopic techniques (Raman, infrared and energy-dispersive X-ray) as well as its morphology by scanning electron microscopy and compared to the analogously prepared reduced graphene oxide (rGO) and ruthenium oxide hexacyanoferrate (RuOHCF) thin films spectra and images. The results suggest that the improvement of the nanocomposite electrochemical activity is generated by the well-distributed RuOHCF nanometric particles over high-surfaced graphene sheets. Ethanol electrochemical oxidation in the rGO/RuOHCF modified electrode was performed in 0.1 mol L-1 NaCl (pH = 1.5) solution and it showed an anodic current peak starting at 0.9 V. Scan rate tests exhibited a diffusion-controlled process not followed by any coupled chemical reaction. The determination of ethanol by amperometry coupled with batch injection analysis (BIA) system resulted in a wide linear range (20-400 mmol L-1) and good sensitivity (0.150 µA L mmol-1). The nanocomposite also showed application as an electrochemical sensor of ethanol in commercial samples mainly because of its easy preparation comparing to biosensors.

Resumo em Inglês:

A highly efficient and reusable catalyst QA-HPMV was successfully prepared by the reaction of quinoline-2-formic acid (QA) with molybdovanadophosphoric heteropolyacid (H4PMo11VO40, HPMV) for the nitration of benzene. The physical and chemical properties of the sample was characterized by X-ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FTIR), UV-Vis and thermogravimetric analysis (TG). The characterization results showed that the formed QA-HPMV retained the Keggin structure of HPMV. As a catalyst for benzene nitration, QA-HPMV showed good catalytic performance and the yield of nitrobenzene was 82.5% under the optimized reaction conditions. As a heterogeneous catalyst, QA-HPMV can be easily recycled from the reaction medium by filtering and remained highly catalytic performance even after five runs of recycling.

Resumo em Inglês:

Shrimp residues generated by the seafood industrial processing are generally discarded in the environment without any further treatment, leading to a loss of nutritional value such as proteins, lipids, chitin, carotenoids, and minerals. This practice can lead to environmental problems due to the decomposition of these substances in the air. The objective of this study was to extract astaxanthin-rich materials from shrimp (Litopenaeus vannamei) industrial residue (WO) and smaller-scale residue meal (MO) in processing shrimp with soybean oil to evaluate their physicochemical characteristics, fatty acid content, and antioxidant potential. WO and MO were found to contain 27.48 and 33.34 µg g -1 of astaxanthin, respectively. The physicochemical properties of pigmented oils are established by legislation. The MO material showed significantly higher antioxidant activity compared to the soybean oil (control), especially when based on the oxygen radical absorbance capacity (ORAC) test, which showed antioxidant activity of 0.484 and 0.264 µmol eq Trolox g -1 for the MO and soybean oil (control), respectively, possibly accompanying their respective astaxanthin contents in the MO sample. The pigmented oils from both the shrimp residues showed significant potential for being used in the food industry due to their affordability and their high antioxidant activity.

Resumo em Inglês:

Brazil has the greatest plant diversity on the planet, distributed in different types of biomes. These plants are important sources of biologically active natural products, which are derived from various drugs marketed worldwide. This paper presents an electrochemical study of three unusual dimeric flavonoids, pharmacologically active, isolated and identified for the first time by our research group, in a Brazilian plant (Fridericia platyphylla). The results showed that oxidation processes are favored at higher pH, and mass transport was controlled by diffusion. Brachydins derivatives, Bra-A was oxidized at the lowest potential value (0.48 V vs. Ag/AgCl, KCl(sat)) and Bra-B and Bra-C, presented the highest oxidation potentials (ca. 0.71 and ca. 0.57 V vs. Ag/AgCl, KCl(sat), respectively). This study shows that electrochemistry is one more tool that would help us focus on future bio-pharmacological investigations of these unusual compounds.

Resumo em Inglês:

Polyesters of xylitol and succinic acid were prepared yielding from 70 to 75% by enzyme-catalyzed esterification using a molar mass from 1:1 to 2:5 at 120 and 140 °C employing from 1 to 10% m/m of enzyme. Control over branching degree was achieved by tuning the reaction conditions (temperature, time, comonomer ratio, enzyme content). This one-step process from renewable starting materials avoids protection-deprotection techniques, as well as the use of toxic solvents by introducing limonene as solvent for polyesterification for the first time. All materials were structurally characterized by infrared (IR) and nuclear magnetic resonance (NMR) spectroscopy, their thermal properties were studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), and the molecular weight of samples were obtained by gel-permeation chromatography (GPC).