Resumo em Inglês:

This paper presents arsenic speciation studies by high-performance liquid chromatography with inductively coupled plasma-mass spectrometer (HPLC-ICP-MS) using a chromatography column containing a strong anion exchange stationary phase (Agilent Bio SAX G3154A/101) for determination of arsenobetaine (AsB), dimethylarsinic acid (DMA), AsIII, monomethylarsonic acid (MMA), and AsV. The best separation was achieved in 15 min, using a 4 min isocratic step with 1 mM (NH4)2HPO4 pH 10.2, followed by a 2 min salt gradient from 1 to 10 mM, which was kept for 4 min. Compared to the Food and Drug Administration (FDA) method for rice using the PRP-X-100 column, the Bio SAX method was quicker, provided at least equal separation of AsB from the next peak, and led to more symmetrical peaks. The linearity between 0.5 and 60 µg L-1 was shown. The method was tested with 10 µg L-1 fortified rice and fish samples extracted in ultrasound using methanol/water 1:1, and recoveries between 40 and 90% were obtained.

Resumo em Inglês:

Clinical studies have identified that an excessive exposure of UV light can cause oxidative stress (OS) and tyrosinase enzyme over-expression, which are associated with multiple diseases including atherosclerosis, cancers, diabetics, rheumatoid arthritis. In this study, we investigated the impact of grape seed proanthocyanidin (GSPE) on regulating OS and tyrosinase activity in human epidermal melanocytes. This study revealed that GSPE did not affect cell viability and protected cells from UV induced damage in a dose-dependent manner. 5-(-6)-Carboxy-2,7-di-chlorodihydro-fluorescein diacetate staining (i.e., a fluorescence staining for intracellular (OS)) indicated that GSPE reduced OS level caused by UV exposure. A similar trend was also confirmed by flow cytometry analysis, where GSPE down-regulated OS level. Tyrosinase analysis showed that GSPE treatment decreased tyrosinase activity. Taken all data together, GSPE may restore the cellular damage caused by excessive UV-exposure and promote skin health by reducing tyrosine generation. Clinically, GSPE could be potentially utilized for improving skin health against excessive UV exposure.

Resumo em Inglês:

An improved and simpler method for the synthesis of benzodiazepin-2,5-diones and 7-iodobenzodiazepin-2,5-diones catalyzed by glacial acetic acid using isatoic anhydride and 6-iodoisatoic anhydride, respectively, as starting materials is reported. The target products were achieved in good yields (up to 71%) using microwave irradiation as the activating mode of reaction in the presence of acetic acid instead of the traditional polar aprotic solvents as dimethylformamide (DMF), dimethyl sulfoxide (DMSO) or dimethylacetamide (DMAC). Moreover, relatively simple purification workup is required. The optimal temperature to obtain the benzodiazepin-2,5-dione derivatives was 130 ºC, while the best irradiation time was 3 min. In addition, the methodology for the selective preparation of 6-iodoisatoic anhydride with an overall yield of 62% is presented.

Resumo em Inglês:

The investigation of the distribution of antioxidant compounds between emulsions phases, employing natural sources of these compounds directly in the emulsions, is rarely addressed. The use of ultra performance liquid chromatography coupled to a mass spectrometer (UPLC-MS), combined with accelerated oxidation tests and oxygen radical absorbance capacity method (ORAC), using the fluorescein (FL) decay curve (ORACFL) assay, enable an improved evaluation of the distribution of the antioxidant compounds and their lipid protection abilities. The lipid protection tendency observed was in agreement with the polar paradox theory. The ORACFL results reported here are higher than other reported in the literature, even when performing a sample extraction directly into one of the emulsion phases, thus demonstrating the effectiveness of this direct addition regarding the antioxidant activity. The analysis of the mass spectra of the emulsions enabled to verify the existence and distribution of some phenolic compounds in both phases. The direct extraction in the aqueous and oil phases of the emulsion increased, in a general way, the amount of identified compounds in each phase.

Resumo em Inglês:

The purification of the hexanic extract from the leaves of a native variety of mahogany collected in Santarém (Pará, Brazil) afforded eight new phragmalin limonoids along with eight known compounds. This variety, according to field observations, should be considered resistant against the specialist insect Hypsipyla grandella, that attacks the terminal shoots only of juvenile mahogany and not of matured ones. After observing that four phragmalin limonoids were present just in mature leaves, we carried out two bioassays, one of them using a fraction from hexanic extract of mature leaves and another using a mix of four limonoids. The results of the bioassay using the isolated limonoids showed a direct effect on the larvae of H. grandella, suggesting that these limonoids act as inhibitors of larvae growth. This should be the reason why larvae choose the young leaves for their development.

Resumo em Inglês:

The removal of the beta-lactam antibiotics (ceftriaxone and cefadroxil) through zero-valent copper nanoparticle (nZVC) was studied in this work. Excellent removal degrees (> 85%) were obtained for both analytes in only 20 min of reaction. Studies were performed in both oxic and anoxic conditions, and in the presence of t-butyl alcohol (TBA), an inhibitor of radicals. The results did not show significant changes. Therefore, the hydroxyl radicals are not the main species responsible for the removal. Total organic carbon cefadroxil analysis indicated a removal of 57% after 180 min of reaction. Studies involving Cu+ indicated that probably these are the principal species responsible for the removal of antibiotics. Kinetic studies have shown that two-phase reaction occurred in the antibiotics removal process and both phases followed pseudo-first order kinetic model. The first mechanism is related to the antibiotics degradation by Cu+ species and the second mechanism is related to the antibiotics adsorption by hydroxides/oxides of Cu2+ species.

Resumo em Inglês:

In this work, enantiopure 1,1’-bi-2-naphthol (BINOL) derivatives and carboxylic acids were evaluated as chiral solvating agents (CSAs) in the nuclear magnetic resonance (NMR) chiral discrimination of primary amines. Among the CSAs screened, the readily available (+)-BINOL revealed a simple and rapid chiral auxiliary for 1H NMR chiral discrimination. The procedure required few minutes, assigning of the absolute configuration. The protocol was improved using the 1H pure shift pulse sequence for overcrowded alkyl primary amines due to the absence of JHH couplings. The 1H pure shift NMR experiment and the readily available (+)-BINOL chiral auxiliary can be used for routine chiral discrimination analysis of complex NMR spectra.

Resumo em Inglês:

Due to the amount of pigments, sugars and fibers found in fruits, the fatty acid quantification process leads to errors, such as its amount underestimation in the matrix. Therefore, the proposed method allows performing experiments in shorter time with reduced amount of sample and reagent. Design Expert software was used to find the validated time for alkaline and acidic reactions, which were six and eight minutes, respectively, and both concentration was 0.5 mol L-1. The validation was made for avocado pulp and different fruits were used for application of the method, such as: apple, mango, coconut and another avocado variety. Accuracy values ranged from 89.05 to 100.21%, being in accordance with acceptable values. Also the relative standard deviation (RSD)intra-day (0.30 to 1.30%) and the RSDinter-day values (0.32 to 1.44%) confirmed that the proposed method for fatty acid derivatization has good precision.

Resumo em Inglês:

This study aimed to use a differential pulse voltammetric (DPV) assay, based on the electroreduction of oxygen, to evaluate the antioxidant capacity of pequi pulp. The results were expressed in coefficient of antioxidant capacity (K), at different pH values and in trolox equivalent antioxidant capacity (TEAC), and were compared to the 2,2’-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) spectrophotometric assays. The principal component analysis showed higher K for pequi pulp extract and pH tending to 7.15. The antioxidant capacity was related to the presence of gallic acid in its composition. Regarding the TEAC value, the best result was obtained by the DPV test (53.43 ± 5.14 µmol trolox g-1 pulp). The pequi pulp showed antioxidant capacity, compared to the standard antioxidant compounds evaluated. It was concluded that the voltammetric protocol was efficient to assess the total antioxidant capacity of pequi pulp and can be an alternative to conventional spectrophotometric assays, for the analysis of food matrices.

Resumo em Inglês:

The amorphous, mesoporous SiO2-SO3H catalyst with a surface area of 115 m2 g-1 and 1.32 mmol H+ per g was very efficient for the protonation of ketones on a 10% (m/m) basis, and the catalyst-bound intermediates can be trapped by polyalcohols to produce ketals in high yields or suffer aldol condensations within minutes under low-power microwave irradiation. The same catalyst can easily reverse the ketalization reaction.

Resumo em Inglês:

Fatty acid esters (methyl and ethyl) prepared from babassu nut oil were blended with the respective esters from soybean oil. These binary blends (babassu:soybean) were made in proportions of 10:90, 20:80, 30:70, 40:60, and 50:50 (vol%). The ester content of all the blends was higher than 96.5%, which is the minimum value required by the Brazilian National Agency of Petroleum, Natural Gas and Biofuels (Agência Nacional do Petróleo, Gás Natural e Biocombustíveis, ANP). The thermal properties of the babassu, soybean and binary mixtures of esters were investigated by thermogravimetry-differential thermogravimetry (TG/DTG) and differential scanning calorimetry (DSC). The thermal stability of the blended biodiesels decreased as the total contents of the babassu esters increased. From the experiments it was found that babassu methanol biodiesel is stable up to 49.6 ºC and the ethanol biodiesel is stable up to 53.7 ºC in air. The methyl esters blends were thermally stable up to 83.2 and 56.8 ºC, for 90:10 and 50:50 blends (soybean:babassu), respectively. The ethyl ester blends presented values of temperature ranges somewhat higher than the methyl esters, such as 85.2 and 64.5 ºC for 90:10 and 50:50 blends, respectively. The esters from babassu oil have satisfactory performance at low temperatures with respect to the point of crystallization, which were below –9.8 ºC for ethylic esters and –8.5 ºC for methylic esters. A good correlation between the crystallization onset temperature and the increase in the concentration of the babassu oil esters was obtained in the mixtures analyses. In the 50:50 combination (babassu:soybean), the crystallization onset temperature were –6.73 and –9.12 ºC for methyl and ethyl esters, respectively.

Resumo em Inglês:

A series of manganese-based catalysts supported on foamed metal nickel (FMN) with various Mn/Ni ratios was prepared for low-temperature selective catalytic reduction (SCR) of NO with NH3 (NH3-SCR). The effects of calcination temperature, amount of added Mn, optimal operating conditions, and H2O on the elimination of nitrogen oxides (de-NOx) performance of catalysts were studied. The catalysts were characterized by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and temperature-programmed desorption experiments of NH3 analyses. The experimental results revealed that the Mn7.5/FMN catalyst calcined at 350 ºC exhibited the best NO conversion that was ca. 100% at 120-200 ºC. Moreover, it had excellent H2O tolerance. The superior activity of the Mn7.5/FMN catalyst, which was calcined at 350 ºC, was attributed to the presence of amorphous manganese oxide, more unsaturated Ni atoms and structural defects, an increase in NH3 adsorbance, and the number of surface acid sites. Based on these studies, we established that the reaction of the NH3-SCR with Mn7.5/FMN catalyst mainly exhibits an Eley-Rideal mechanism.

Resumo em Inglês:

Microscopic techniques were combined to study the influence of corrosion rate on the morphologic behavior of AISI 1020 steel specimens submitted to thermal degradation of a typical acid crude oil (total acid number (TAN) = 2.1390 mg KOH g-1 and total sulfur (S) = 0.7778 wt.%). The techniques used were light microscopy (LM), scanning electron microscopy/energy dispersive spectroscopy (SEM/EDX), atomic force microscopy (AFM) as well as Raman spectroscopy. Assays were performed in six different degradation time (t = 6, 12, 24, 36, 48 and 72 h) at 320 ºC. After the exposure of the specimens to petroleum, a reduction above 37% in the TAN after t = 72 h was observed, with a maximum corrosion rate during the first periods of degradation (t = 6 and 12 h). Correlating the TAN and corrosion rate data with the microscopic data, the images of LM, AFM, and SEM/EDX showed that after 6 h of exposure to petroleum, a passivation film was formed on the surface of the steel. This film consisted of two layers, an external one, formed of FeS, and an internal one, composed of iron oxides and oxyhydroxides. However, after 48 h of thermal degradation, this morphology was altered to a single layer of FeS coating the steel surface.

Resumo em Inglês:

Iodine value is an important quality parameter for evaluation of the oxidative stability of biodiesel and vegetable oils, but the official methods are time-consuming and demand large amounts of reagents and solvents. The present work describes a novel procedure for determination of iodine value based on the discoloration of a triiodide aqueous solution due to halogenation of the unsaturated compounds in the samples. Iodine is extracted to the organic phase and consumed proportionally to the amount of unsaturated compounds in the samples. Thus, the remaining fraction of I3- quantified by spectrophotometry in the aqueous phase is inversely proportional to the concentration of unsaturated compounds. For biodiesel samples, responses were linear from 10 to 106 g I2 per 100 g, with coefficient of variation and limit of detection estimated at 5.0% (n = 8) and 2.5 g I2 per 100 g, respectively. The corresponding values for vegetable oils were 20 to 140 g I2 per 100 g, 3.0% (n = 10), and 7 g I2 per 100 g, respectively. The procedure consumed only 1.2 mL of sample, 365 µg of I2, and 42 mg of KI with ca. 2.4 mL of waste generated per determination. The results agreed with those obtained by the official methods at the 95% confidence level.

Resumo em Inglês:

One new natural product, 1-phenylethyl-O-a-L-rhamnopyranoside, together with eight known diketopiperazines and two benzene derivatives were isolated from the endophytic fungus Colletotrichum crassipes, whereas six known compounds including two griseofulvins, three cytochalasins and one dihydroisocoumarin were produced from the endophyte Xylaria sp., both endophytic fungi are associated with leaves of Casearia sylvestris. Cyclo(D)-Pro-(D)-Phe, N-(2-phenylethyl)acetamide and 5-carboxy-6-hydroxy-3-methyl-3,4-dihydroisocoumarin exhibited potent antifungal activity against Cladosporium cladosporioides and C. sphaerospermum. The compounds cyclo(D)-Pro-(D)-Phe, griseofulvin, cytochalasin B and cytochalasin D exhibited antioxidant activity, and the compounds cyclo(D)-Pro-(D)-Phe, cytochalasin B and cytochalasin C showed potent acetylcholinesterase (AChE) inhibition. In addition, this is the first report on the isolation of secondary metabolites from two endophytic fungal strains, associated with Casearia sylvestris.

Resumo em Inglês:

New application of modified silica aerogel nanoparticles was carried out for adsorption of Vietnamese spilled crude oil obtained from Bach-Ho field. The aerogel was synthesized by atmospheric drying method without critical extraction procedure in liquefied CO2 followed by surface modification using polydimethylsiloxane precursor in n-hexane solvent. The synthesis mixture contained precise amounts of water, tetraethyl orthosilicate (TEOS), ethanol and HCl with volume ratios of 2:1:4:0.0003, respectively. The modification was established by the mixing of the as-synthesized aerogel and polydimethylsiloxane followed by calcination at 350 ºC for 4 h obtaining the surface modified aerogel. The modified aerogel was applied in the adsorption of the spilled crude oil in mild temperature and atmospheric pressure. Some techniques such as X-ray diffraction (XRD), transmission electron microscopy (TEM), Brunauer-Emmett-Teller surface area analysis (BET) and Fourier transform infrared spectroscopy (FTIR) were used for characterizing the materials.

Resumo em Inglês:

Carbamazepine is an antiepileptic drug which is considered one of the persistent compounds detected in Malaysian aquatic environment. In this present study, a full factorial experimental design was applied for the analysis of effect NaCl amount, initial concentration of carbamazepine, applied voltage and treatment time on the electrochemical removal percentage of carbamazepine. However, applied voltage was found as the most significant factor with p = 0.00 lower than 95% confidence level. The investigation of effect NaCl and Na2SO4 on the pathway degradation for carbamazepine was provided using liquid chromatography-time of flight/mass spectrometry (LC-TOF/MS). The results showed that new by-products were identified such chloro-epoxy carbamazepine, and other by-products, were detected in the presence of NaCl and Na2SO4 electrolytes. High inhibition percentage of Escherichia coli (E. coli) bacteria was observed at 24.0 h incubation time for both NaCl and Na2SO4 electrolytes after 80 and 20 min of treatment, respectively.

Resumo em Inglês:

The aim of the present study is to assess the potential of ethanol deriving from the mesocarp of babassu coconut to be used in fuel cells. Babassu ethanol was generated through hydrolysis and fermentation processes. The Pt, PtRh and PtRu electrodes were prepared in carbon Vulcan XC72R through the reduction method and applied as electrocatalysts in ethanol oxidation reaction. X-Ray diffraction (XRD), energy-dispersive X-ray (EDX), stripping CO, cyclic voltammetry, chronoamperometry, and online differential electrochemical mass spectrometry (DEMS) were used to characterize the synthesized eletrocatalysts. The electrocatalyst Pt80Ru20/C presented larger active area and higher catalytic activity than other studied materials. The current efficiency of CO2 production rated less than 1% in all studied electrocatalysts, thus showing that babassu ethanol oxidation produces less pollutants than the commercial ethanol.

Resumo em Inglês:

This study evaluated the incorporation of β-carotene, lutein and lycopene into tilapia (genetically improved farmed tilapia, GIFT) fillets supplemented through 0, 20 and 40 days, and their influence on the fatty acid composition and nutritional quality of raw and grilled fillets. A control diet and a diet containing those carotenoids were elaborated with the same lipid source (soybean oil). For carotenoids analysis, the extraction was performed according to the literature, employing acetone and hexane. The relative intensities of m/z ratios of those carotenoids ions were obtained by ultraperformance liquid chromatography-tandem mass spectrometry with chemical ionization at atmospheric pressure (UPLC-APCI MS/MS), and an increase of carotenoid concentration in the supplemented fillets was observed, especially after the grilling process (180 ºC for 15 min). An increase in the concentration of total carotenoids in grilled fillets (75 and 35% higher than raw fillets, for 20 and 40 days of supplementation, respectively, corresponding to 8.32 and 2.42 µg β-carotene g-1 sample) was also observed. Therefore, the carotenoids promoted the stability of lipid oxidation in grilled samples; fact that can be correlated with antioxidant effect of these compounds, it can be also explained by the breakdown of carotenoids physical barrier and the conditions used in the grilling process. Moreover, acceptable n-6/n-3 indices and recommended polyunsaturated fatty acids/saturated fatty acids (PUFA/SFA) values were observed in supplemented fillets. Consequently, lutein, β-carotene and lycopene were considered viable as additive on fish diet, since the supplementation promoted the increase of food quality, even after preparation for consumption.

Resumo em Inglês:

The synthesis of a new N-heterocyclic carbene with bulky S-arylthiocarbamate substituents was devised from the condensation between 2-chloromethyl-4-methy-l,6-[3,5-bis(trifluoromethyl)-phenyl]-S-phenyl-N,N-dimethylthiocarbamate and imidazole, resulting in the proligand N,N’-bis[(2-S-(N’’,N’’-dimethylthiocarbamoyl)-5-methyl)phenylmethyl]imidazolium iodide [H(S-carb)2NHC]I. This newly synthesized proligand was crystallographically characterized, thus confirming its identity; its stability was established in several solvents, resulting in air oxidation in methanolic solution, giving rise to the decomposition product N,N’-bis[(2-S-(N’’,N’’-dimethyl ­thiocarbamoyl)-5-methyl)phenylmethyl]-4,5-dimethoxyimidazolyl-2-one. Reaction of the proligand with silver oxide afforded the corresponding complex [(S-carb)2NHC]AgI, which was fully characterized by spectroscopic techniques.

Resumo em Inglês:

Graphite was incorporated to a polydimethylsiloxane (PDMS) polymer network functionalized with amino groups to obtain an electrode material and used to detect copper ions in aqueous solutions and sugarcane spirit. The polymer network was prepared with PDMS, 3-aminopropyl-trimethoxysilane (APTMS), tetraethyl orthosilicate (TEOS) with addition of graphite to obtain the electrode material. The materials were prepared with different mass concentrations of PDMS: 0, 3, 6, 12 and 18%; and characterized by thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR). Quasi-reversible behavior was found when studying the [Fe(CN)6]3-/4- redox probe and were electrochemically stable up to 100 consecutive cycles. Electrochemical impedance measurements showed a second time constant at high frequencies for the PDMS electrodes, indicating a second phase in the polymer network with resistive properties, probably due to an increase in the material polymerization resistance. Square wave voltammetry studies were conducted with these electrodes to detect copper(II) ions in aqueous solution. The electrode proposed was applied to determine Cu2+ in a real sample, sugarcane spirit. The PDMS electrodes prepared here presented a potential to be applied as electrochemical sensors for detecting copper ions.

Resumo em Inglês:

The objective of this study was to evaluate the effect of whole cottonseed on diets of cows under grazing on fatty acid profile and milk cholesterol. Five crossbred Holstein × Zebu cows were distributed in a 5 × 5 Latin square. Inclusion levels were 0, 6, 12, 18 and 24%. There was a linear decrease in all fatty acids quantified, saturated and monounsaturated (p > 0.05), possibly due to the action of polyunsaturated fatty acids ingested in the diet. There was no influence of treatment on conjugated linoleic acids or cholesterol. It is concluded that, regardless of inclusion level, there is a modification in the milk lipid profile, reducing the concentration of saturated fatty acid, monounsaturated fatty acid, and making it rich in polyunsaturated fatty acids, which are beneficial to health.