Resumo em Inglês:

The solar-to-chemical energy conversion is promising to tackle sustainability challenges toward a global future. The production of H2 from sunlight represents an attractive alternative to the use of carboniferous fossil fuels to meet our energy demands. In this context, the water splitting reaction photocatalyzed by semiconductors that can be excited under visible or near-infrared light excitation represents an attractive route to the clean generation of H2. In this review, we present an overview of the most important concepts behind the H2 generation, from water splitting, promoted by semiconductor-based systems for readers that were recently introduced to the water splitting topic. Then, we present the main classes of photocatalysts based on semiconductors. For each class of semiconductors, we focused on the examples that lead to the highest activities towards the H2 production and discuss the operation principles, advantages, performances, limitations, and challenges. We cover metal oxides, sulfides, and nitrides. We also discuss strategies in which these materials are combined, including hybridization with metal nanoparticles, other semiconductors, and carbon dots, to achieve improved performances and circumvent the limitations of the individual counterparts.

Resumo em Inglês:

Asphaltenes constitute the heavy petroleum fraction responsible for deposition events that may lead to reduced oil production, therefore of great interest for flow assurance. These molecules self-assemble in solutions leading to formation of aggregates that eventually grow towards precipitation and blockages in reservoirs and pipelines. Based on the Yen-Mullins aggregation model, two complementary scenarios are involved in asphaltenes phase behavior: one called thermodynamic, in which interacting molecules and other species can be assumed to be in equilibrium, and a second one, involving interacting colloidal particles, both being described by different theoretical frameworks. For the first, molecular interactions can explain the experimental observations or theoretical models. For the second stage, colloidal forces such as those described by Derjaguin, Landau, Verwey and Overbeek (DLVO) theory, steric particle stabilization and diffusion or reaction limited aggregation processes might control the process. Our evaluation is that this second approach is underrepresented in the current literature. For this reason, this review focuses on describing evidences for the presence of colloidal particles in crude oils obtained with different experimental techniques, drawing attention to this important attribute and we raise a few questions that we believe must be addressed in order to better understand the contributions from colloidal aspects.

Resumo em Inglês:

A series of functionalized 1,1,1-trihalo-4-methoxy-3-alken-2-ones [CX3C(O)CR1=CROMe, where X = F or Cl; R = n-heptyl, n-octyl, n-nonyl, n-decyl, n-undecyl, n-tridecyl, (CH2)2CH=C(Me)2, (CH2)2Ph, (CH2)2-(4-HOC6H4), (CH2)2-(4-MeOC6H4), (CH2)2CO2Me, (CH2)3CO2Me, CH(SMe)CH3, CH2(2-MeOC6H4), and R1 = H, and R = H and R1 = n-decyl] were synthesized from respective alkyl methyl ketones or aldehyde via acetal acylation using trifluoroacetic anhydride and trichloroacetyl chloride. 1,1,1-Trihalo-4-methoxy-3-alken-2-ones with acid-compatible substituents were easily hydrolyzed to respective trihalomethyl-1,3-diketones. The 1,1,1-trihalo-4-methoxy-3-alken-2-ones and/or respective trihalomethyl-1,3-diketones were reacted regiospecifically with hydroxylamine hydrochloride, leading to isoxazole derivatives, and with hydrazines, leading to respective 1H-pyrazole derivatives. The structures of all compounds were assigned based on nuclear magnetic resonance (NMR) and mass spectrometric data. This method represents an efficient pathway for the regioselective trihaloacetylation of asymmetrically substituted alkyl methyl ketones and highly self-condensing aldehydes. Moreover, this approach allows the introduction of biologically recognizable moieties, such as those from levulinic acid, sulcatone (prenyl), benzylacetone, anisylacetone, and raspberry ketone, as synthetic molecular targets.

Resumo em Inglês:

Our study aimed at the development of a method based on ultra-performance liquid chromatography coupled to mass spectrometry (UPLC-ESI-MS) using selected ion monitoring for the simultaneous quantitation of the alkaloids galantamine, pseudolycorine, sanguinine and narciclasine in Amaryllidaceae species (Hippeastrum elegans, Habranthus cf. irwinianus, Hymenocallis littoralis and Griffinia nocturna). The alkaloids were extracted from dried and ground bulbs (100 mg) using liquid-liquid microextraction followed by solid phase extraction in cation exchange cartridges. The quantification method showed good linearity (correlation coefficient, R ≥ 0.9968) and selectivity for a run time of 10 min. All values were within the acceptable limits for recovery (87.5-96.2%), interday (coefficient of variation, CV%, 1.3-8.4%) and intraday precision (CV% 5.7-8.1%), except narciclasine (70%). The limits of detection and quantification were 5-100 and 20-350 ng mL-1, respectively. Our method demonstrated to be rapid, sensitive and reliable, therefore appropriate for being employed in the prospection of new source of galantamine and other alkaloids.

Resumo em Inglês:

The aims of the current study are to investigate the composition of biomass from baru processing and to explore the feasibility of valuing it through the development of bioproducts such as fermentable sugars, furanics and biochar. Baru (Dipteryx alata Vog.) waste (endocarp and mesocarp) has great energetic potential to produce bioproducts due to its chemical composition. Proximate analyses applied to such waste have found low favorable moisture and ash content in it. Bioproduct characterizations after acid hydrolysis have shown that baru endocarp and mesocarp biomass can enable a range of value-added products in biorefinery concepts such as furfural and 5-hydroximetylfurfural (20.0 and 1.5% yield, respectively), and high sugar content (approximately 19.15 and 38.40%, respectively). Pyrolysis processes also present high biochar content (ca. 48%), with satisfactory characteristics to be used as fuel, as well as calorific value higher than 30 kJ g-1.

Resumo em Inglês:

A series of fenofibric acid ester pro-drugs (JF-1-7) were synthesized. The pharmacokinetic properties of these pro-drugs were examined after oral administration to rats at a dose of 20 mg kg-1 to evaluate the relative bioavailability in rats. The bioavailability of the ester compounds, JF-1, 2, 3, 4, 5, 6, and 7, was significantly higher than that of fenofibrate. In particular, JF-2 proved to be most promising. The oral administration (20 mg kg-1) of JF-2 showed a relative bioavailability of approximately 272.8% compared to fenofibrate.

Resumo em Inglês:

A novel method for the synthesis of nonsymmetrical 3,3’-(aryl/alkyl-methylene)bis-2-hydroxy-1,4-naphthoquinones was developed by using the Mannich adduct of naphthoquinone and the reaction with another moiety of 2-hydroxy-1,4-naphthoquinone. This novel method produces for the first time nonsymmetrical 3,3’-(aryl/alkyl-methylene)bis-2-hydroxy-1,4-naphthoquinones. In a preliminary study, these compounds (15c, 15f and 15h) were evaluated regarding their effect over the viability of PC3 metastatic prostate cancer cell using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays at 100 µM. Three of these compounds presented relevant cytotoxic effects at 72 h posttreatment.

Resumo em Inglês:

In this work, the direct determination methodology of glyphosate and aminomethylphosphonic acid (AMPA) by high performance liquid chromatography (HPLC) using inductively coupled plasma with triple quadrupole mass spectrometer (ICP-MS/MS) was compared with the conventional method using diode array detector (HPLC-DAD). Both methods were selective, but the chromatographic analysis using ICP-MS/MS as detector was four times faster than DAD. The methodology using ICP-MS/MS as detector was linear from 27 to 218 µg L-1, while by the conventional method it was 1 to 8 mg L-1. Detection limits of the glyphosate achieved with the HPLC-ICP-MS/MS and HPLC-DAD methods were 8.2 and 300 µg L-1, respectively. The direct determination using ICP-MS/MS as detector showed a lower number of stages in sample preparation because it did not need the derivatization step. Seven real samples were analyzed by HPLC-ICP-MS/MS and the results showed that these analytes were not detected.

Resumo em Inglês:

Introducing a hybrid xanthene as a fluorophore, an ‘ensemble’-based fluorescent sensor (E)-2-(6-(diethylamino)-2-((2-hydroxyphenylimino)methyl)-3-oxo-3H-xanthen-9-yl)benzoic acid (a) was designed and synthesised for detection of cysteine. Cysteine can release CuII ion from the non-fluorescent a-CuII complex. Then hydrolytic cleavage of Schiff base a produces a pink fluorescent compound 2-(6-(diethylamino)-2-formyl-3-oxo-3H-xanthen-9-yl)benzoic acid (2). We call this process a fluorescence off-on change. An obvious color change from purple a to pink 2 can be easily observed by the naked-eye. The calibration curve showed that the fluorescence intensity at 560 nm linearly increased over the cysteine concentration range of 0.379-100 µmol L-1 with a limit of detection of 0.379 µmol L-1. Sensor a-CuII displayed excellent selectivity for cysteine, even homocysteine and glutathione did not show influence. The sensor was also used for detecting cysteine in human breast adenocarcinoma cells, which illustrates the practical value. Overall, the sensor appears to be useful for rapid, convenient and selective cysteine detection in living tissues.

Resumo em Inglês:

The use of biodiesel as fuel has been presented as a viable alternative in the search for renewable energies. It can be produced from the transesterification reaction of vegetable oils with methanol in the presence of sodium or potassium hydroxide as catalysts. In the present research, the transesterification reaction of soybean oil was modeled considering the three steps of the direct and reverse reactions following a second order general kinetics by the finite element method using the COMSOL Multiphysics® software. The values of rate constants were determined using the simplex optimization method coupled with the desirability functions. The optimized rate constants for the forward reactions were 0.250 × 10−6 (k1f), 1.137 × 10−6 (k2f) and 3.134 × 10−6 (k3f); and for the reverse reactions were 0.202 × 10−6 (k1r), 0.884 × 10−6 (k2r) and 0.219 × 10−6 (k3r) all in m3mol−1s−1. The kinetic model proposed for the reaction can be simulated by the finite element method (FEM) under realistic conditions.

Resumo em Inglês:

In this study, biopolymer-based pH-sensitive hydrogels have been successfully prepared using alginate, κ-carrageenan and pectin aimed at the encapsulation of pancreatin (hydrolytic enzymes like α-amylase, lipase and protease) so as to preserve enzymatic activities. Hydrogels have been characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), swelling degree and swelling profile. Encapsulation efficiency and in vitro studies on delayed release have also been evaluated. All hydrogels presented low swelling degree and enzyme release in a gastric medium. On the other hand, high swelling degree and enzyme release were observed in an intestinal medium. Alginate hydrogel achieved optimal results concerning encapsulation efficiency (18, 68 and 53% for α-amylase, lipase and protease, respectively) and delayed release (363, 7,673 and 17,497 U for α-amylase, lipase and protease, respectively) which has been afterwards compared to a commercial pancreatin formulation (CreonTM 10,000). Thus, it presented better performance than its commercial formulation, mainly in respect of lipase.

Resumo em Inglês:

Agroindustrial residues, such as leaves of fruit plants, can be sources of bioactive molecules, thus adding value to co-products that are rarely explored in agroindustry. In this context, this study aimed to look into the phytochemical profiles in detail and to explore the antitumor potential of S. tuberosa and S. mombin leaves. We observed that, S. tuberosa leaf extract was cytotoxic in both tumor and healthy cells. S. mombin extracts selectively inhibited cell proliferation in the tumor cell line for prostate cancer (PC3) and did not significantly affect healthy cells. The metabolic profiles of the extracts were evaluated by gas chromatography coupled with mass spectrometry and twenty-three metabolites were identified. The correlation of metabolic profiles with cytotoxic tests indicated possible chemical markers that may be responsible for the inhibition of cell proliferation. This study revealed that the unexplored co-products in agroindustry may have great therapeutic potential, and therefore should be screened for biologically active compounds.

Resumo em Inglês:

The chemical composition of Acacia mearnsii wood extract is described in this paper for the first time. This wood is cultivated in Brazil and has been used to complement the demand for hardwood in the pulp industry. In this study, we performed extractions with acetone (total extracts) and dichloromethane (lipophilic extracts responsible for the pitch formation), with the obtained percentages being 1.68 and 0.68%, respectively. The lipophilic extracts were derivatized and analyzed by Fourier transform infrared spectroscopy (FTIR) and gas chromatography-mass spectrometry (GC-MS) before and after alkaline hydrolysis. The results showed that 57 compounds were detected in the lipophilic extracts and these are mainly constituted by fatty acids ca. 32.8 mg kg-1 and sterols 26.9 mg kg-1. These chemical classes have always been present in pitch deposits in the pulp industry. Therefore, these results may be used by pulp mills to establish strategies for pitch control and represent an important advance in the knowledge of A. mearnsii.

Resumo em Inglês:

Endopleura uchi (Huber) Cuatrec. is an Amazonian medicinal plant with restricted distribution to the North Region of Brazil. Its bark is commonly used as natural medicines for the treatment of many diseases. Although widely investigated from the phytochemical viewpoint, the knowledge regarding the phenolic content remains unexplored. In order to access the phenolic composition of E. uchi bark, an integrative approach based on simplex-centroid design, direct infusion electrospray ionization mass spectrometry (ESI-MS) and chemometric analysis was adopted. In addition, the extracts were evaluated to total phenolic content and antioxidant activity. The multivariate analysis pointed to the ethanol-based extracts as the most representative for phenolic compounds, with 3,5-di-O-galloylquinic acid (2), gallic acid (4), 5-galloylquinic acid (5) and gallocatechin gallate (6) tentatively identified by MS analysis, all described for the first time in E. uchi. Besides, pure ethanol extract presented highest total phenolic content (TPC = 133.61 ± 0.3 mg GAE 100 g-1) and antioxidant activity (half maximal inhibitory concentration, IC50 = 9.32 ± 0.15). The integrative approach proposed to this work provided an effective way to assess the phenolic compounds of E. uchi bark, therefore, improving the knowledge regarding phenolic content in this Amazonian medicinal plant.

Resumo em Inglês:

Marine strains of Bacillus are known to produce secondary metabolites different from that accumulated by their terrestrial counterparts, for example, lipopeptides such as surfactins, iturins and fengycins, which exhibit a variety of biological activities. Another important class of lipopeptides are pumilacidins, identified specially from Bacillus pumilus strains, usually by using liquid chromatography-mass spectrometry (LC-MS) techniques. In this work, five knowns pumilacidins were isolated from the solid culture of the marine-derived bacterium Bacillus sp. 4040. The structures of compounds, pumilacidins A-E, were determined using a combination of mass spectrometry, nuclear magnetic resonance (NMR) spectroscopy and comparison with reported data. The 1H and 13C NMR data of pumilacidin B is being described here for the first time. All compounds were evaluated against five microorganisms, but no antimicrobial activity was detected.

Resumo em Inglês:

The endophytic fungus Microsphaeropsis arundinis was isolated from the capitula of the tropical plant Paepalanthus planifolius (Eriocaulaceae). The fungus was cultivated in seven different media, and the ethyl acetate extracts were tested against tumor cell lines using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide MTT assay. The culture was scaled up using parboiled rice medium, and the crude extract was purified by classical chromatographic analyses, leading to the isolation of seven compounds. The seven compounds isolated from the culture media included a new aromatic polyketide (1) and other known metabolites. The structures of all the compounds were elucidated by 1D and 2D nuclear magnetic resonance (NMR) and high resolution mass spectrometry (HRMS) analyses. An evaluation of the cytotoxicity of all the isolated compounds showed that these compounds exhibit less activity in comparison with the extract cultured in parboiled rice.

Resumo em Inglês:

A graphite-polyurethane composite electrode (GPUE) was modified by electrodeposition of copper nanoparticles (CuNP) followed by electrochemical treatment in NaOH (GPUE-CuNP), in order to prepare an amperometric sensor for the determination of cysteine (Cys). Cyclic votammograms of Cys solutions at GPUE-CuNP allowed the description of a sequence of electrochemical reactions involving Cys oxidation and Cu/Cu+ equilibrium, generating a stable Cys-Cu+ complex. The presence of these nanoparticles was confirmed by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) data. Hence, the developed device was then used as a Cys amperometric flow detector in a wall-jet system, after evaluation of flow injection parameters in an undescribed approach. In this system, a limit of detection (LOD) of 4.24 µmol L-1 was obtained with an analytical frequency of 36 determinations h-1. Intra-day and inter-day reproducibility and repeatability of the modified surface was evaluated. Then the GPUE-CuNP performance was investigated in the determination of Cys content in food supplements. Interference tests were carried out with pyridoxine, ascorbic acid, tryptophan and SO4 2- ions. The main interference was attributed to the interaction of some of these substances with copper oxides.

Resumo em Inglês:

Lithium manganese oxide, LiMn2O4, was synthesized in two temperature stages, where the first consisted by an ecofriendly solution combustion method at 300 °C. Finally, the as-burned powders were thermal treated at 500 and 700 °C. The structural and morphological changes were evaluated by the Rietveld method and density functional theory (DFT) calculations. The Rietveld refinement indicates obtaining the spinel cubic phase LiMn2O4 and a small amount of Mn2O3. The analyses by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) show a porous microstructure composed of nano-sized crystallites for the sample treated at 500 °C. In cyclic voltammetry, it was possible to observe that the reduction-oxidation reaction is reversible due to the shape of voltammograms and the anodic and cathodic peaks of Mn ions. The theoretical calculations considered the experimental crystallographic parameters. The unit cell volume change was evaluated according to distinct amounts of lithium ions in the structure. The removal of the Li+ cations from the oxides promotes a volume contraction. Therefore, it was possible to evaluate the participation of the Mn3+ ions in the frontier region between the valence and conduction bands. The density of states (DOS) calculation shows a predominant contribution of the O 2p and Mn 3d orbitals in the frontier orbitals.

Resumo em Inglês:

Despite the efforts of the pharmaceutical industry to reduce the ethanol content in medicines, many of these products are still commercially available. These medicines must be monitored by quality control techniques using accurate method. Therefore, this study proposes to develop and validate an analytical method for ethanol quantification in adult and pediatric syrups, in order to guarantee the safety of medication certificates. For this, headspace multidimensional gas chromatography (heart-cut) coupled to mass spectrometry (HS-MDGC/MS) was used. The method was validated according to the norm established by National Agency of Sanitary Surveillance (ANVISA) presenting limit of detection (LOD) of 0.03% (v/v) and limit of quantification (LOQ) of 0.06% (v/v) ethanol, excellent selectivity and the recovery values (accuracy) were between 96.71 and 101.38%. Ethanol concentrations in commercial medicines syrups varied from 0.06 to 8.83%, which makes evident the need to control the syrup producing industries.

Resumo em Inglês:

This work reports the theoretical and experimental study of fragmentation reactions in the gas phase of five phenolic acids using triple quadrupole mass spectrometry by electrospray ionization in negative ionic mode, as well as the isotope exchange experiments. MS/MS spectra were analyzed to suggest the fragmentation mechanisms, while theoretical calculations at the theory level B3LYP/6-311+G** were performed to expose the proposed mechanisms viability for this class of compounds. As expected, compounds with aromatic methoxy substitution presented •CH3 radical elimination as the principal fragmentation pathway, forming dystonic ions. Compounds without methoxy substituents dissociate with higher energies losing the CO2, CO and H2O. The isotopic marking experiments indicated the exchange of hydrogens by deuterases in the hydroxyl protons, which corroborates with the proposed mechanisms.

Resumo em Inglês:

Siloxane-poly(methyl methacrylate) (PMMA) hybrid was synthesized based on the sol-gel method and applied to Ti-6Al-4V through dip-coating. The structural feature of the hybrid was subjected to Fourier-transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TG); its morphological properties were analyzed through scanning electron microscope (SEM), energy dispersive spectrometry (EDS), atomic force microscopy (AFM) and contact angle. The electrochemical behavior and corrosion resistance of both the hybrid coating and the uncoated substrate were investigated based on electrochemical impedance spectroscopy (EIS) and scanning vibrating electrode technique (SVET). Results showed homogeneous coating formation due to the rigid hybrid network formed during polymerization, hydrolysis and condensation reactions. This outcome suggested interaction between the organic (methyl methacrylate (MMA)) and inorganic (tetraethyl orthosilicate (TEOS)) phases, which was favored by the coupling agent (3-(trimethoxysilyl)propyl methacrylate (TMSM)). The S0M (PMMA-SiO2 hybrid Ti-6Al-4V coated alloy) film presented regular topography and adherence to the substrate. Electrochemical simulated body fluid (SBF) tests showed that the hybrid coating presented better barrier properties (168 h of the immersion time) than the uncoated substrate, fact that makes it an interesting material for anti-corrosive applications in biomaterials.

Resumo em Inglês:

The use of paper devices in chemical analysis has been increased due to their low cost, high surface area, portability, and biodegradability. A novel use of paper devices is proposed using thermal infrared enthalpimetry (TIE) for a rapid, green, and high throughput determination of wine acidities. The determination of total, fixed, and volatile acidities in red, white, and sparkling wine was carried out, and the results were compared with AOAC titration method. A multichannel pipette was used for reagent addition and an infrared camera for the temperature monitoring. The pipetting and temperature measurement conditions presented direct influence in the deviations among the measurements. The results obtained by TIE presented an agreement between 96 and 104% with the reference method (AOAC 962.12), for all samples. A high sample throughput was achieved reaching 480 samples h-1 for total acidity. A significant reduction in sample volume and reagent consumption was also obtained, with energy consumption up to 60 times lower in relation to the AOAC method. The association of TIE with a paper device provided a rapid, reliable and green method for the determination of acidities of wines.