Resumo em Inglês:

Raman imaging spectroscopy is a relatively new technique that has raised interest in several areas of knowledge due to the possibility of evaluating the spatial distribution of compounds based on their spectra. This paper presents a brief history of the development of this important technique, a theoretical description of the Raman effect and the preprocessing and processing (both univariate and multivariate) tools for Raman data. We also describe the current state of applications for major areas such as agriculture/biomass, environment, biology, medicine, pharmaceutical, geology, foodstuff, artwork, archaeology, material characterization and forensic.

Resumo em Inglês:

The present manuscript makes an extensive review of the scientific approaches developed in the last decade involving infrared and Raman spectroscopy combined with chemometrics for solving several issues in the investigation of the most relevant forensic traces, such as questioned documents and currency, explosives, gunshot residues, illicit drugs and body fluids. In addition, current trends, main challenges and the adequate use of several chemometric techniques are discussed. Principal component analysis (PCA) was found to be the most used technique. This unsupervised approach, however, has sometimes been misunderstood as a classification technique. Discriminant analysis techniques are widely employed, leaving a range of possibilities for application of class-modeling techniques, particularly in cases of problems regarding only one target class. In addition, increasingly complex dataset structures frequently require nonlinear approaches or flexible techniques such as multivariate curve resolution-alternating least squares (MCR-ALS). Results reporting, however, still lack reliable quality parameters and sample representativeness, posing a significant challenge to the solution of forensic problems. Regarding the analytical techniques, Raman has been playing an important role, especially in the area of questioned documents and of body fluids. Portable and hyperspectral imaging infrared spectrometers have also been showing significant potential in forensic applications.

Resumo em Inglês:

In this study, P. divaricatum (Piperaceae) plants were subcultured by cuttings and cell tissue in order to carry out a comparison of the volatile profile, phenolic compounds, and antioxidant activity. Propagation by cuttings used vermiculite substrate and Murashige-Skoog (MS) medium in the absence of growth regulators and rooting started at 15 days of growth providing a higher number of plants after 90 days. In vitro propagation was performed using shoot apices as explants in MS media supplemented with 0.5 mg mL-1 BA (6-benzyladenine). Volatile profiles analyzed by gas chromatography-mass spectrometry (GC-MS) showed as main compounds methyl eugenol, E-β-ocimene, and β-elemene in the in vivo and in vitro cultures. Phenolic contents determined by the Folin-Ciocalteu method had no significant difference at the end of 90 days of growth displaying a good linear correlation with antioxidant activity and phenylpropanoids amounts (r > 0.7). However, the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging was higher for in vitro plants grown in comparison to in vivo plants cultured.

Resumo em Inglês:

[Ag(HL)NO3] complexes (1-4) were obtained with (E)-N’-(1-(2-methyl-5-nitro-1H-imidazol-1-yl)propan-2-ylidene)acetohydrazide (HL1); (E)-N’-(1-(2-methyl-5-nitro-1H-imidazol-1-yl)propan-2-ylidene)benzohydrazide (HL2); (E)-2-(1-(2-methyl-5-nitro-1H-imidazol-1-yl)propan-2-ylidene)hydrazinecarbothioamide (HL3) and (E)-N-methyl-2-(1-(2-methyl-5-nitro-1H-imidazol-1-yl)propan-2-ylidene)hydrazinecarbothioamide (HL4) secnidazole-derived Schiff bases. In addition, complexes [Bi(HL3)Cl3] (5) and [Bi(HL4)Cl3] (6) were also prepared. The silver(I) complexes (1-4) showed antifungal activity against Candida fungal strains while the uncomplexed ligands and the bismuth(III) complexes (5-6) were inactive, suggesting that the antifungal effects are probably due to the presence of silver. Although the Schiff base ligands and complexes (1-6) revealed to be inactive against Gram-positive and Gram-negative aerobic bacteria, all compounds exhibited potent antimicrobial effects against several anaerobic bacterial strains, indicating that their mode of action probably involves anaerobic bio reduction of the nitro group, with formation of metabolites which are toxic to the microorganisms. Electrochemistry studies showed that bio reduction of the nitro group is favored in complexes (1-6) in comparison to the free ligands, which might, at least in part, explain their increased antimicrobial effects.

Resumo em Inglês:

We describe an on-flow zonal affinity-based chromatography assay to screen ligands for the nucleoside diphosphate kinase B enzyme (NME2) from Homo sapiens. For the first time, we have covalently immobilized NME2 on the surface of an open fused silica capillary reactor (NME2-ICER) and placed the reactor before the analytical column, which resulted in a two-dimensional liquid chromatography-based system. We evaluated the pH effect on immobilized NME2 activity and carried out steady-state kinetic studies to compare free and immobilized NME2. Steady-state kinetic studies with the substrates adenosine 5’-triphosphate di(tris) salt dihydrate (ATP) and guanosine 5’-diphosphate sodium salt (GDP) resulted in apparent Michaelis-Menten constant values of 1136 and 713 mmol L-1, respectively. The ping-pong catalysis mechanism and substrate specificity were preserved after NME2 immobilization. By employing a reference inhibitor, (-)-epicatechin gallate (ECG), we verified the potential application of this method in NME2 ligand screening and NME2 inhibitor identification. The half maximum inhibitory concentration (IC50) for ECG was 161.3 ± 1.0 μmol L-1.

Resumo em Inglês:

Chitosan is a biodegradable aminopolysaccharide produced by deacetylation of acetamide groups of chitin, one of the most abundant organic materials in nature. Many different types of organic reactions have been described to modify the functional groups of chitosan and produce materials with applications in a large number of areas. However, the Zincke reaction, an old method which is commonly used to convert primary amine in pyridinium salts, has not been reported to transform the chitosan amino group at C-2 position in glucosamine units. In this paper, our efforts are described to carry out this reaction, employing different conditions to covalently anchor pyridinium salts on the polymer surface. Optimized synthesis conditions using water/ethanol as solvent, triethylamine and Zincke salt excess yielded a novel polycationic chitosan-pyridinium derivative with a weight gain of 52% after 48 h of reaction. The modified biopolymer is water insoluble and exhibits a high degree of chemical modification. The 13C solid state nuclear magnetic resonance (SS-NMR) spectrum of chitosan-pyridinium derivative showed signals at 147.0, 142.0 and 129.0 ppm, attributed to aromatic carbons, confirming the presence of a quaternary pyridinium ring directly attached to the biopolymer. The Zincke reaction was employed for the first time to modify the chitosan backbone.

Resumo em Inglês:

Previous studies on Passiflora edulis (sour passion fruit) rinds reported some biological activities and there is a growing interest on rinds flour as a possible functional food, but its alkaloid composition was not detailed investigated. This work reports on for the first time in the literature the identification of norharman in P. edulis rinds, by using stir bar sorptive extraction combined with ultra-fast liquid chromatography coupled to tandem mass spectrometry [SBSE(EG-Silicone)-UFLC-MS/MS)]. This β-carboline alkaloid is suspected to be neurotoxic. Therefore, another purpose of this study was to develop methods of targeted quantification of norharman in P. edulis rinds extracts using polydimethylsiloxane as stationary phase (SBSE(PDMS)) and a copolymer of polydimethylsiloxane and polyethylene glycol as stationary phase (SBSE(EG-Silicone)) combined with high performance liquid chromatography with fluorescence detection (HPLC-Flu) and ultra-fast liquid chromatography coupled with tandem mass spectrometry (UFLC-MS/MS). Norharman extraction by SBSE(PDMS) and SBSE(EG-Silicone) was optimized and compared, and the analytical performance of SBSE(EG-Silicone) method was superior to that of SBSE(PDMS). The analysis of a sample of dried P. edulis rind indicated (332.16 ± 8.43) pg g-1 of norharman.

Resumo em Inglês:

Sample preparation of polymers for halogen determination requires special attention because they are difficult to bring into solution and due to the risk of analyte losses when using acid digestion. A method using microwave-induced combustion (MIC) was optimized for accurate determination of halogens in polymeric parts obtained in waste of electrical and electronic equipment. Results were compared with those by using microwave-assisted extraction (MAE) with alkaline solution and microwave-assisted wet digestion (MAWD) using concentrated nitric acid, which are common choices for sample preparation. In this particular case, the MAE method was not suitable and underestimated results were obtained, showing the necessity for the complete digestion. Even with the use of MAWD under high temperature and pressure, incomplete digestion and high acid content were obtained, which were unsuitable for analysis and resulted in poor recovery. Only by using MIC (diluted ammonia as absorbing solution) acceptable recoveries (95 to 104%) and agreement with certified values for the certified reference materials (CRMs) of polymers were obtained. Thus, a suitable method for all halogen to be determined by ion chromatography (IC) or inductively coupled plasma mass spectrometry (ICP-MS), with the exception of F, was obtained in agreement with the requirements by the Restriction of the Use of Certain Hazardous Substances (RoHS) European directive.

Resumo em Inglês:

A polyurethane composite electrode modified with magnetic nanoparticles (mag; Fe3O4) coated with molecularly imprinted polymers (MIPs) was developed for the electrochemical determination of estradiol valerate. Chemical and morphological analyses of the mag-MIP were performed using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS), with the aim of characterizing this new material. The efficiency of adsorption of estradiol valerate by the mag-MIP was tested in binding experiments using an electrochemical method. For this, different electrodes (mag-MIP / graphite-epoxy composite (GEC), mag-non-imprinted polymer (NIP) / GEC, mag / GEC, and GEC) were evaluated by square-wave voltammetry (SWV). After 10 min at open circuit potential, increases in the current signal of 1.9, 2.1, and 3.0 times were obtained, comparing the electrochemical response of the mag-MIP / GEC sensor to the mag-NIP / GEC, mag / GEC, and GEC sensors, respectively. Under optimized conditions, the mag-MIP / GEC showed a linear concentration range for estradiol valerate of 5.0 × 10-7 to 7.5 × 10-4 mol L-1 and a limit of detection of 1.0 × 10-8 mol L-1. The proposed sensor was applied in the analysis of pharmaceutical, human urine, and river water samples. The recovery values determined using high performance liquid chromatography (HPLC)-UV and the electrochemical method were in agreement and were near 100%, demonstrating the reliability of the proposed method.

Resumo em Inglês:

In this work, carbon dots (CDs) prepared by a one-step hydrothermal method were employed for the determination of quercetin in teas and beers. The fluorescence quenching of CDs was proportional to the concentration of quercetin. Under optimum experimental conditions, linear quenching was observed for quercetin in the range of 1.0 to 10 mg L-1 (F/F0 = (0.1511 ± 0.0075)[Q] + (0.8922 ± 0.0384), R2 = 0.9926), at room temperature, using 80 μL CDs and 0.1 mol L-1 Na2HPO4/NaOH buffer solution (pH 11.0). A limit of detection (3σ criterion) of 0.85 mg L-1, and a relative standard deviation of 0.21% (n = 3) for 4.0 mg L-1 quercetin solution was obtained. Addition and recovery tests with tea and beer samples were performed resulting in recoveries at the range between 80 and 118%. This procedure served successfully to determine quercetin in beer and tea samples presenting high sample throughput.

Resumo em Inglês:

Non-doped (Hap) and doped hydroxyapatites with Cu2+ and Fe2+ were synthesized and used to study the adsorption of furan (Fur), pyrrole (Pyr), and thiophene (Thi) in single and ternary component systems. Spectroscopic data and N2 isotherms indicated there were no structural alterations in Hap with the incorporation of Cu2+ and Fe2+. For both single and ternary components, the incorporation of the metal ions resulted in an adsorption increment consistent with the hard-soft acid-base concept. When comparing the systems, there is an inversion with Thi (5.41 mg g-1) and Fur (5.51 mg g-1) being the most adsorbed species in the single and ternary components, respectively. Monte Carlo simulations helped explain the observed experimental trends. While the electrostatic effect seems to prevail in the single system, in the ternary one the mass transport phenomenon is also operative implying greater availability of Fur on surface leading to its higher adsorption efficiency.

Resumo em Inglês:

Bismuth is a critical metal broadly used in cosmetic, medicine and metallurgy. However, its scarcity in Earth’s crust may impair further applications. An alternative is to recover bismuth from secondary sources. In this work, a methodology to extract bismuth from safety valves of discharged gas cylinders is proposed. Extraction and purification of bismuth were carried out using aqueous two-phase systems (ATPS) prepared with poly(ethylene oxide) polymer or poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) copolymer (L35) and electrolytes (NaNO3, NH4NO3, sodium citrate or Na2SO4). The influence of iodide extractant concentration, tie-line length, electrolyte nature and polymer hydrophobicity on the bismuth extraction behavior were evaluated. Bismuth was significantly recovered in the absence of extractant, and its extraction depends on the ATPS composition, macromolecule and electrolyte nature. After three consecutive extractions bismuth was obtained with high purity (94.7%), resulting on a recovery of 38.5 g of bismuth per 1.00 kg of fusible plug, using L35 + NH4NO3 + H2O ATPS, without any extractant.

Resumo em Inglês:

Clomazone exhibits high water solubility, low sorption in soil colloids, and therefore can leach and contaminate deep layers of soil profile and groundwater. In this work, the effect of the incorporation of sugarcane bagasse biochar in leaching and bioavailability of clomazone in red latosol was evaluated. Soil samples amended with 1% (m/m) biochar were placed in different depths (0-1, 0-2.5 and 0-5 cm) on the top of polyvinyl chloride (PVC) columns filled with soil. Clomazone-based herbicide was applied, and rainfall was simulated on top of the columns. A validated chromatographic method, together with a greenhouse bioassay, were used to quantify and to evaluate the mobility and availability of clomazone along the columns. The incorporation of sugarcane bagasse biochar in the superficial layers at the column tops increased herbicide sorption, reduced its leaching and bioavailability in soil and scaled down the environmental risk of clomazone avoiding contamination of underground aquifer reservoirs.

Resumo em Inglês:

An analytical method for the determination of Al, Ca, Cd, Cr, Cu, Fe, Hg, K, Mg, Na and Zn in breast of conventional, country and Christmas chicken and turkey samples using microwave induced plasma optical emission spectrometry (MIP-OES) technique was developed. Samples were decomposed in a digester block with a reflux system under conditions optimized using a central composite design as it follows: 2 g of sample, in 7.5 mL of HNO3 during 180 min at 160 °C. The accuracy was evaluated by the analysis of standard reference material SRM 1546 meat homogenate (94 to 108%) and also by addition and recovery tests (80 to 121%). The highest concentrations, in mg kg-1, of Al (2.77), Ca (88.3), Cu (1.99), Fe (3.65), K (3236), Mg (292.62) and Na (312.03) were found in the breast of conventional chicken sample. Zinc presented high value in the breast of turkey sample (10.6 mg kg-1). However, the found concentrations were lower than the daily consumption limit established by supervisory agencies and reference limits from Brazilian legislation. Cadmium, Cr and Hg presented values below limit of quantification. In this way, it is evident that chicken breast should be consumed in a complementary way in a healthy diet.

Resumo em Inglês:

Chemotherapy treatment of leishmaniasis is based on the use of pentavalent antimonials, but these drugs present low efficacy and high toxicity. In the search for new antileishmanial agents, essential oils (EOs) from four Croton species (C. argyrophylloides, C. jacobinensis, C. nepetifolius and C. sincorensis) were evaluated against Leishmania infantum chagasi, L. amazonensis and L. braziliensis. EOs were analyzed by gas chromatography combined with mass spectrometry. Spathulenol, β-caryophyllene, β-caryophyllene oxide, 1,8-cineole and methyl eugenol were the major constituents. The evaluation of antioxidant activity by the 1,1-diphenyl-2-picryl-hydrazyl (DPPH) method showed that all EOs have moderate antioxidant activity. All oils were similarly active against L. i. chagasi, and C. nepetifolius EO showed the best result against L. amazonensis, with median inhibitory concentrations (IC50) of 9.87 μg mL-1, similar to amphotericin B (IC50 = 7.38 μg mL-1). The oils presented low cytotoxicity in macrophages. The in silico analysis revealed that spathulenol and 1,8-cineole were active against the enzyme Leishmania infantum trypanothione reductase (LiTR), showing excellent interaction energies, making them promising agents for leishmaniasis control.

Resumo em Inglês:

Four new complexes of formula [Fe(H2pcpa)2(H2O)2] (1), {[Mn(Hpcpa)(H2O)3]•1/2H2O}n (2), {[Zn(Hpcpa)(H2O)3]•1/2H2O}n (3) and [Cu2(Hpcpa)2(bipy)2]•8H2O (4) [H3pcpa = N-(4-carboxyphenyl)oxamic acid; bipy = 2,2¢-bipyridine] have been synthesized and their structures determined by X-ray diffraction. The structure of 1 consists of mononuclear iron(II) units where each iron(II) ion is six-coordinate by two trans-positioned water molecules and two bidentate H2pcpa- ligands building a distorted octahedral environment. 2 and 3 consist of neutral zigzag chains of MnII and ZnII ions respectively, the Hpcpa2- groups acting as linkers in a bidentate/monodentate coordination mode with three mer-positioned water molecules achieving the six-coordination around the metal centers. Compound 4 is a neutral centrosymmetric dicopper(II) complex where two Hpcpa2- groups adopting the bidentate/monodentate coordination mode and act as bridges and bidentate bipy molecules act as end-cap ligands, describing a square pyramidal surrounding around each copper atom. Cryomagnetic measurements for 1, 2 and 4 in the temperature range 1.9-300 K reveal the occurrence of a field-induced single-ion magnet (SIM) behavior (1) and weak interchain (J = -0.22 cm-1, 2) and intradimer (J = -0.39 cm-1, 4) antiferromagnetic interactions, the Hamiltonian being defined as H = -J Sa.Sb.

Resumo em Inglês:

Hyptis pectinata (L.) Poit is a folk medicinal species in Northeast Brazil. In this work, seedlings of H. pectinata were cultured in vitro under diverse light quality spectra and under the influence of two distinct chemical elicitors, salicylic acid and silver nitrate (SN), at concentrations of 30 and 60 μM. Growth parameters, biomass and rosmarinic acid (RA) content were evaluated. RA may be associated with the functional properties of this plant. In the light quality experiments, the highest level of rosmarinic acid was found under red light (161.65 ± 8.64 μg g-1 DW (dry weight)) at 20 days (4.26-fold higher than the control white light). Among the evaluated elicitors, elicitation with 60 μM SN at 3 days and 30 μM SN at 6 days favored the highest rosmarinic acid content (6361.70 ± 216.96 and 4542.98 ± 92.53 μg g-1 DW, respectively), with relatively high biomass yield and a similar number of leaves and height as those of control seedlings. This approach is new for H. pectinata.

Resumo em Inglês:

Electrochemical methods are considered useful tools for simulations of biological redox reactions. The activities of quinones depend on their bioreduction. Biologically active pterocarpanquinones LQB-149 (nitroderivative), 150 and 151 (bromo and chloroderivatives, respectively) were electrochemically investigated by cyclic voltammetry, differential pulse voltammetry, and in situ UV-Vis spectroelectrochemistry, in aprotic media (N,N-dimethylformamide (DMF) + tetra-N-butylammonium (TBAPF6)). The data obtained regarding their reduction mechanisms, positive reactivity with oxygen and analysis of the electrogenerated intermediates were useful in explaining their biological outcomes. The appearance of bands at 397 and 480 nm, for the halogenated compounds, suggests the generation of transient quinonemethides (QM), electrophilic intermediates related to their activity. As an additional proof for the intermediacy of QM, in the redox processes, chemical reduction of LQB-150, in the presence of hexanethiol was performed and led to a thioalkylated quinone. For the nitroderivative, a broad band appeared at 432 nm, corresponding to the generation of the nitroradical anion, giving rise to a dianion diradical, after reduction at the second wave potential. Computational data correlate well with electrochemical experiments. Homogeneous electron transfer to oxygen, yielding reactive oxygen species, the generation of electrophilic species and the radical reactivity, explain partially the mechanism of biological action.

Resumo em Inglês:

An alternating magnetic field (AMF)-stimuli responsive nanodevice based on magnetic nanoparticles (MNP) functionalized with water-soluble carboxylate-substituted pillar[5]arene (CP[5]A), namely MNP-CP[5]A, as a multiplatform for cancer treatment has been designed. MNP-CP[5]A was loaded with doxorubicin (DOX), showing a loading capacity of 9.5 mg g-1. The nanodevice demonstrated good colloidal stability, superparamagnetic behavior, and was capable to generate detectable heat in solution induced by AMF application. DOX release, monitored by ultraviolet-visible (UV-Vis) spectroscopy, was investigated by varying the temperature (37 and 45 °C) without AMF and in the presence of AMF (frequency (f) = 307 kHz, field amplitude (H) = 200 Oe, 45 °C) at pH = 7.4. Thermo-induced DOX release without AMF was 1.9% (1.8 μg mL-1) and 2.3% (3.3 μg mL-1) at 37, and 45 °C within 50 min, respectively. In an AMF DOX release increased to 5.7% (8.2 μg mL-1) within 50 min. Therefore, MNP-CP[5]A-DOX works as a chemo-hyperthermia nanodevice.

Resumo em Inglês:

Molecular phylogenetic studies separated and united a group of genera that constituted the Spathelia-Ptaeroxylon clade, in which Dictyoloma and Sohnreyia have been included. Our taxonomic interest in the Dictyoloma vandellianum and Sohnreyia excelsa stimulated an investigation of both species searching for limonoids. Leaves from D. vandellianum afforded the new limonoid 1,2-dihydro-1α-hydroxy-8,30-epoxy-cneorin R, and heartwood yielded the new rearranged limonoid dictyolomin. Leaves from S. excelsa afforded the new protolimonoid 3β-angeloyloxy-7α,24,25-trihydroxy-21,23-oxide-14,18-cycloapotirucall-21-methoxycetal and the new cycloheptanyl ring C limonoid with carbonate substituent and named as sohnreyolide. The new limonoids from Sohnreyia and Dictyoloma show similarities with those from Rutaceae and Meliaceae, providing support for moving Spathelia-Ptaeroxylon clade near to these associated large families.

Resumo em Inglês:

A comprehensive study of a less harmful functionalization of multiwalled carbon nanotubes (MWCNT) was performed. The influence of ultrasonic cavitation and solid/liquid interface was indirectly evaluated by statistical characterization of MWCNT aspect ratio and degree of functionalization. MWCNT aspect ratio was determined through hundreds of electron microscopy images. Degree of functionalization of MWCNT was characterized by elemental analysis and thermogravimetry. Distribution of different oxygen-containing functional groups was assessed by potentiometric titration. MWCNT aqueous dispersions were evaluated by electrophoretic mobility and dynamic light scattering. An acid volume over 90% lower than usually reported in literature guaranteed MWCNTs with significantly larger aspect ratio, higher proportion of carboxylic groups and a more negative zeta potential in aqueous suspension. These results can be related to a more localized ultrasonic cavitation in MWCNTs/acid interface for reduced liquid volumes. This distinguished influence of ultrasonic cavitation may be a valuable contribution to more eco-friendly processes with nanomaterials.

Resumo em Inglês:

The functionalization of graphene oxide with organosilanes is an important strategy to yield graphene-silica composites as well as to create nanomaterials for use as reinforcement in polymer nanocomposites and corrosion-inhibiting coatings for metals, among other uses. However, depending on the reaction conditions used, the organosilanes tend to self-condense, encapsulating the graphene oxide in a silica-like layer which can impair its properties by hiding its real surface and two-dimensionality. In this paper we describe a facile route for the functionalization of commercial graphene oxide with (3-aminopropyl) triethoxysilane using low concentrations and mild reaction conditions, and yielding amine and silanol surface-modified graphene nanohybrids while preserving its two-dimensional characteristics. The material obtained was characterized by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), potentiometric titration, thermogravimetric analysis and electronic microscopy, evidencing the covalent and superficial nature of the functionalization.