Resumo em Inglês:

Azlactones are useful building blocks in the synthesis of functional amino acid derivatives, heterocycles and bioactive molecules. In this work, a protocol for the organocatalytic functionalization of dipeptides has been presented. 2-Alkyl-substituted azlactone intermediates in the presence of different amines and alcohols were combined in a ring opening reaction approach. The products were synthesized in moderate to excellent isolated yields, providing new insights in peptide transformations involving carbodiimide activation.

Resumo em Inglês:

Soils with high levels of iron and aluminum, thus negatively the phosphorous availability, affecting crop yields. A prior determination of the soil capacity to adsorb phosphate is relevant to attaining good agricultural performance. To this end, a multi-pumping flow system with pulsed fluidization is proposed. The procedure takes into account the amount of remaining phosphorus (P-rem) in the solution after the adsorption step to indirectly estimate the soil retention capacity. A 1.0 mg L-1 P solution is passed through a fluidized bed column with 50 mg of soil (particles < 0.15 mm), where the analyte is adsorbed. P-rem was spectrophotometrically quantified by the molybdenum blue method. The coefficient of variation (n = 20), limits of detection and quantification (99.7% confidence level), and sampling rate were estimated as 1.54%, 17 and 51 µg L-1 P, and 87 h-1, respectively. Only 0.27 mg (NH4)6Mo7O24 and 0.10 mg SnCl2 were consumed per determination, generating 2.4 mL of waste. The results followed a linear relationship [y = 0.9702x + 1.483 (r = 0.9635; n = 20)] with the reference procedure. In comparison to the reference procedure, 100, 40 and 180-fold reductions in the required soil amount, waste generation and analytical time were attained.

Resumo em Inglês:

The introduction of oxygen groups in carbon nanotubes is considered crucial for many applications. However, there is a lack of controlled functionalization methods which ensure nanotubes with specific property values according to each interest. In this work, acid treatments of multiwalled carbon nanotubes (MWCNTs) employing an optimized ultrasound process with moderate heating and stirring were studied by means of a factorial design. The functionalized nanotubes were characterized by thermogravimetry, elemental analysis, Raman spectroscopy, electron microscopy and water stability tests. Statistic models were fitted for the degree of functionalization and length reduction of MWCNTs. Temperature was identified as a key parameter to produce more functionalized MWCNTs with less structural damage. The properties of the functionalized MWCNTs can be tailored by the choice of parameters exploited in the statistical models developed to enable different end-use requests, such as for polymeric composites or bio-related applications, which is the original contribution of this work.

Resumo em Inglês:

In this work, we have synthesized CdTe quantum dots (QDs) dispersed in an aqueous medium at ambient temperature, and investigated their optical properties. Synthesis of CdTe QDs in the presence of simple amines removed the need for an additional energy source and inert atmosphere, in a simple and inexpensive experimental setup. The use of ammonia or hydrazine promoted nanoparticle growth by kinetic nanocrystal agglomeration in the initial growth stage. These weak electrolytes acted in the electrical double layer during the growth of the nanocrystals. A comparative study on the concentration of hydrazine in the reaction medium helped to investigate their role in nanocrystal growth. Substitution of hydrazine for ethylenediamine and other electrolytes like sodium chloride and ammonium chloride contributed to a better understanding of the mechanism that underlies the use of primary amines in the synthesis of CdTe. The synthesis conditions afforded the highest photoluminescence quantum yield for CdTe QDs prepared at room temperature (27.5%).

Resumo em Inglês:

Vitamin A and its esters are commonly found in topical applications because of their advantageous properties, however, have the drawback that are highly sensitive to ultraviolet radiation. The aim of this work was to develop and characterize a novel formulation of solid lipid nanoparticles suitable for topical applications in order to protect vitamin A from degradation. Vitamin A-loaded nanoparticles were successfully prepared by hot homogenization employing Gelucire 44/14® and cetyl alcohol as carrier materials, showing an entrapment efficiency of more than 90%. Particle size, measured by dynamic light scattering, was ca. 40 nm, while transmission electron microscopy images showed that dried nanoparticles were spherical with an average size of about 30-50 nm. Small angle X-ray scattering was used to study their aspect ratio and their physicochemical properties were evaluated by differential scanning calorimetry, infrared spectroscopy and X-ray powder diffraction, additionally, stability of vitamin A was studied by UV-Vis spectroscopy.

Resumo em Inglês:

In this study, lipase from Candida antarctica B (Lipozyme CaLB-L) was successfully immobilized on SiO2 through adsorption and used to obtain (R)-(+)-esters derived from (R,S)-1-phenylethanol. The new immobilized enzyme was compared with commercially immobilized lipases (Novozyme 435, Lipozyme 435 and Pseudomonas cepacia (PSC-II and PSD-I)). Lipozyme CaLB-L adsorbed onto SiO2 was found to be a good catalyst and, under optimal conditions, esters could be obtained with conversion 44%, enantiomeric excess of product (eep) > 99%, enantiomeric excess of substract (ees) 77% and enantiomeric ratio (E) > 200. The lipase maintained enantioselectivity under adverse conditions, such as in organic solvents, with an excess of substrate and at different temperatures. The immobilized lipase could be reused five times with no significant loss of the activity.

Resumo em Inglês:

Nickel was electrodeposited from choline chloride (ChCl)-based deep eutectic solvents (DESs) containing ethylene glycol (EG) and urea (U) on Cu substrate. The influence of the temperature and of DESs nature was evaluated. The diffusion coefficients of nickel varied from 2.2 × 10-9 to 3.7 × 10-8 cm2 s-1 for ChCl:2U and from 1.3 × 10-8 to 5.8 × 10-8 cm2 s-1 for ChCl:2EG with increasing temperature. The nucleation process of Ni on Cu at 70 °C was determined as instantaneous in ChCl:2EG and progressive in ChCl:2U using Scharifker and Hills model. The SEM characterization showed that with increasing temperature, more compact coatings were obtained. Linear polarization and electrochemical impedance spectroscopy were used to evaluate the corrosion performance of the obtained deposits in 3.5% NaCl. The coatings were more protective as higher the temperature of deposition, with polarization resistance (Rp) values from 3.53 to 19.11 kΩ cm2.

Resumo em Inglês:

The profile of volatiles emitted by Ilex paraguariensis, leaves of which are used to produce a popular South American tea, were identified and compared among treatments. Headspace collections were performed for 24-72 hours for control, mechanical damage (MD), herbivory by larvae of Thelosia camina (TC), and by adults of Hedypathes betulinus (HB). Based on gas chromatography-mass spectrometry (GC-MS) and gas chromatography-Fourier transform infrared (GC-FTIR) analyses, 20 compounds were identified, totaling about 7, 5, 20, and 25 µg/plant/treatment (control, MD, TC and HB, respectively). Statistical analyses revealed that control and MD treatments are different from TC and HB herbivory treatments. Furthermore, HB herbivory was distinctive from the other treatments at 24 h in that HB feeding induced a distinctive pattern of emission of terpenes. Major compounds per treatments were decanal for control and DM, 4,8-dimethylnona-1,3,7-triene (DMNT) and 2-undecanone for TC, and DMNT and (E)-β-ocimene for HB.

Resumo em Inglês:

In this work, a simple electrochemical biosensor for 4-chlorophenol was developed based on laccase immobilized on a hybrid nanocomposite (ZnO nanoparticles/chitosan), and incorporated in a carbon paste electrode. There are few biosensors in the literature for this specific pollutant because it tends to form polymeric films on the electrode, causing surface passivation or even enzyme inactivation. The carbon paste allowed the surface to be easily renewed by polishing, which amends this limitation. To optimize the experimental conditions, we used cyclic voltammetry and hydroquinone as a representative of phenolic compounds due to the high toxicity of chlorophenol, thus avoiding the generation of hazardous residues. After optimization, a calibration curve was constructed for 4-chlorophenol using differential pulse voltammetry, and a linear response was obtained from 1 to 50 µM, with a lower detection limit of 0.7 µM. The obtained biosensor showed high accuracy when employed in the analysis of industrial wastewater.

Resumo em Inglês:

Food security has become a major concern of the world population and this is even more prominence in polluted areas. This study aimed to evaluate microbiological and toxic elements content of local food itens from Santo Amaro, Bahia. The determination of lead, cadmium, Escherichia coli (E. coli) and total coliform were carried out in coriander, cassava, okra, chicken muscle/liver, fish muscle and eggs. The population of total coliform and E. coli were estimated by the express count method using plates EC (AOAC 991.14) and accounting of colonies by colony counter. For toxic elements determination samples were digested using HNO3 and H2O2 following EPA 200.3 using a digester block with cold fingers. The determination of lead and cadmium was performed by inductively coupled plasma optical emission spectrometery (ICP OES). The mean total coliform has ranged from < 1 to 4.5 log CFU g-1. Coriander presented higher mean total coliform (4.5 log CFU g-1) and E. coli was higher than recommended levels. The range of toxic elements revealed higher concentrations of lead in chicken muscle (1.25-11.58 mg kg-1) and cadmium in eggs (0.45-1.06 mg kg-1). Finally, the risk to the inhabitants of Santo Amaro was evident and reinforces the importance of effective actions of local authorities.

Resumo em Inglês:

Binding between bovine serum albumin (BSA) and a plumeran indole alkaloid (PIA) isolated from the stem bark of Aspidosperma cylindrocarpon (Apocynaceae) was studied by spectroscopic techniques (UV-Vis absorption, circular dichroism, steady state and time-resolved fluorescence), combined with molecular docking. Steady state and time resolved fluorescence data revealed that PIA can quench the BSA fluorescence via a static mechanism: energy transfer from BSA to PIA occurs with high probability. The binding is strong (Kb ca. 105-106 L mol-1), spontaneous (ΔG° ca. -35.7 kJ mol-1 at 310 K) and entropy-driven (ΔS° = 0.146 kJ mol-1 K-1). There is just one main binding site (n ca. 1) for the BSA:PIA interaction and the α-helix content of the albumin does not suffer significant perturbation upon PIA binding. Molecular docking results suggest site I as the main binding site to PIA, which is able to interact with the Trp-212, Arg-217, Val-342 and Pro-446 residues.

Resumo em Inglês:

A simple and rapid high performance liquid chromatography coupled with diode array detector (HPLC-DAD) method was developed for simultaneous quantification of three chemical types of bioactive compounds including an alkaloid (epigoitrin), six nucleosides (uracil, cytidine, hypoxanthine, uridine, guanosine and adenosine), and four phenylpropanoids (syringin, clemastanin B, indigoticoside A and isolariciresinol) in Radix Isatidis and its relevant pharmaceutical dosage forms. The developed method was successfully applied to analyze 32 batches of samples with good linearity (R2, 0.9966-0.9999), precisions (relative standard deviation (RSD), 0.24-4.61%), repeatability (RSD, 0.39-4.93%), stability (RSD, 1.18-4.29%) and recovery (range, 95.4-104.6%) of the eleven compounds. The limits of detection (LOD) and limits of quantification (LOQ) of the method ranged 0.0383-0.1744 and 0.1550-0.5467 µg mL-1, respectively. The results indicated that the newly established HPLC-DAD method was sensitive, precise, accurate and reproducible. It could be applied to the quality control of Radix Isatidis and its relevant pharmaceutical dosage forms.

Resumo em Inglês:

A simple, inexpensive, reliable and environmentally friendly method based on ultrasound assisted extraction (UAE) combined with dispersive liquid-liquid microextraction with solidification of floating organic drop (DLLME-SFO) was developed for the simultaneous determination of four triazines in fruit and vegetable samples. Parameters affecting the extraction process were studied and optimized. Under the optimum conditions (sonication time: 15 min; extraction solvent: 30.0 µL 1-undecanol; disperser solvent: 1.0 mL acetonitrile; pH: 7; and extraction time: 0 min), extraction recoveries for different fruit and vegetables are in the range of 65-86%. The calibration graphs are linear in the range of 5-800 µg kg-1, with the correlation coefficient (r2) higher than 0.9985. The limits of detection (LODs) are in the range of 1-2 µg kg-1, which are lower than the maximum residue levels (MRLs) established by various official organizations. Repeatability (intra-day) and reproducibility (inter-day) of the method based on five replicate measurements of 100 µg kg-1 of herbicides were in the range of 3.6-5.4% and 4.5-6.3%, respectively.

Resumo em Inglês:

Magnetic iron oxides are of great scientific and technological relevance. Therefore, herein, we report the research on developing methodologies for their sustainable and reproducible preparation. We discuss the synthesis of iron oxides involving citrus pectin as a source of energy (42 MJ kg-1) to promote the formation of the magnetic phases. The method involved two simple steps: gelation of the pectin (80 °C, 4 h) with iron nitrate nonahydrate [Fe(NO3)3.9H2O], and calcination (600 °C, 1 h). X-ray diffraction indicated the major formation of hematite (α-Fe2O3) and ferrite phases. Microscopy images show materials with an average size below 50 nm. Textural properties indicated pore sizes of 7-30 nm while magnetic measurements indicated the formation of soft and hard oxides (coercivity between 90 and 400 Oe) and high magnetization saturation (50 emu g-1).

Resumo em Inglês:

Pyrimidines and their derivatives are present in various biologically active molecules. Most of the synthetic methods employed to achieve the pyrimidinone ring consist of two stages: the synthesis of a Michael intermediate from an aldehyde and an "active methylene" containing compound; and the condensation of this intermediate with a molecule containing an uranium moiety. This may take one to two days of laboratory work. In this paper we describe a new methodology in which these derivatives are obtained via multicomponent synthesis mediated by ultrasound in only 2 hours. In order to obtain water-soluble pyrimidinone derivatives, our previous compounds were further converted into their sodium salts. In pharmacologic studies, these salts inhibited phenylephrine-induced contraction in isolated rat aorta, suggesting that they may act as alpha-1 antagonists and, therefore, are candidates for anti-hypertensive drugs.

Resumo em Inglês:

This study reports a functional passive sampler for monitoring gaseous elemental mercury (GEM). The material consists of gold nanoparticles (AuNP) deposited forming a film on thiol-modified glass slides. AuNP colloid was synthesized using sodium citrate, resulting in a size of 24.2 ± 0.8 nm, as determined by transmission electron microscopy analysis. For the indoor test, AuNP films were placed into Petri plates. One part of the lot was kept exposed to the laboratory's atmosphere and the other part was stored in closed plate (control). The films were removed from both plates along a month and analyzed using a direct mercury analyzer. A linear relationship between Hg retention and exposure time was obtained until the 23rd day, which allowed to calculate a GEM retention rate of 2.2 ng g-1 day-1; the maximum retention capacity was around 50 ng g-1. This study provides an efficient method for indoor monitoring of GEM using AuNP films as passive sampler.

Resumo em Inglês:

Four new alkaloids, Brazoides A-D, together with three known compounds squalene, β-sitosterol and lupeol, were isolated from leaves of Justicia gendarussa. These structures were established by spectrometric techniques, mainly high-resolution electrospray ionization mass spectrometry (HRESIMS) and 1D and 2D nuclear magnetic resonance (NMR), including comparative analysis with literature values. Structural determination of the compounds, Brazoides A-D, was strengthened by molecular modeling and density functional theory (DFT) calculations to predict the NMR data and compare with the experimental NMR values of these natural products. The new compounds were tested against three human cancer cell lines (glioblastoma, prostate and colon), but none exhibited activity.

Resumo em Inglês:

Medicines containing anabolic steroids are one of the main targets for counterfeiting worldwide, including Brazil. The aim of this work was to propose a method for discriminating original and counterfeit Durateston® ampoules by Fourier transform infrared spectroscopy (FTIR) followed by chemometric analysis. Ninety-six ampoules of Durateston®, 49 originals and 47 counterfeits, were analyzed by gas chromatography with mass spectrometry (GC-MS) and by FTIR. Principal component analysis was applied to the infrared spectra to detected different clusters, corresponding to original samples and different types of counterfeits. A partial least squares - discriminant analysis method was proposed to discriminate original samples from those counterfeits that were indistinguishable from the originals in the infrared analysis. A training subset comprised of one-third of the available spectra was used to establish a suitable model that correctly discriminated all samples in the test subset, resulting in 0% of false positive or negative results and 100% of efficiency rate, sensitivity and specificity. In addition to the low cost of the infrared technique, the proposed method is fast, reliable and suitable to replace GC-MS methods used in Durateston® ampoule analyses to detect counterfeiting.

Resumo em Inglês:

To show liver failure mediated by 5-aminolevulinic acid (ALA), a heme precursor accumulated in inborn and acquired porphyrias, rats were treated with succinylacetone methyl ester (SAME). Treated rats underwent the expected ALA accumulation in plasma, liver and urine as a result from inhibition of ALA dehydratase (ALAD) activity. The enzyme activity decreased concomitantly with diminished urinary coproporphyrin levels. Additionally, liver protein carbonyls, iron and ferritin were higher in groups treated with a lower concentration of SAME whereas malondialdehyde was higher in the group treated with a higher ester dose. Consistent with these biochemical data, chronic treatment SAME was associated with induced oxidative subcellular and tissue damage revealed by cytosolic and mitochondrial changes within the liver cells. Altogether, these data expand the understanding of the direct biochemical mechanism for liver cell death in hepatic inborn disorders by generating excess ALA and may foster future therapeutic-driven strategies to preserve liver function.

Resumo em Inglês:

Roasted and ground coffee is targeted by fraudulent addiction of products. In this way the determination of contaminants in coffee has economic and nutritional importance. In this study, the coffee adulteration by corn were detected using DSC (differential scanning calorimetry) and FTIR (Fourier transform infrared spectroscopy) coupled to PCA (principal component analysis), and PLS (partial least squares) models. Three different levels of roasted and ground Coffea arabica L. were used to prepare mixtures with roasted and ground corn. The level of adulteration used was between 0.5 to 40% (m/m). It was observed that both DSC and FTIR coupled with PCA are able to discriminate adulterated from unadulterated samples of coffee by corn at levels below 1%. PLS models were built with DSC and FTIR data reaching good correlation between the values of estimated and reference concentrations, with RMSECV (root mean square error of cross-validation) lower than 3.5% for DSC data and 2.7% for FTIR data.

Resumo em Inglês:

This study reports the synthesis and characterization of a Ni/Zn layered double hydroxide salt intercalated with acetate ions and the subsequent replacement of the acetate ions with molybdate ions via an ion exchange reaction, conducted at two different pH values. Regardless of the pH employed during the synthesis, the basal spacing in the Ni/Zn layered double hydroxide salt decreased from 13.08 Å to approximately 9.5 Å, which agreed with intercalation of hydrated molybdate anions. The non-calcined material and the material submitted to heat treatment at 250 °C (basal spacing reduced to 7.35 Å, due to dehydration) were tested as catalyst for the methyl transesterification of soybean oil. Like sodium molybdate in homogeneous media, the solid materials were active catalysts. After reaction at 120 °C for 4 h, the materials afforded high conversions at an alcohol/soybean oil molar ratio of 35:1 and preserved the structure after three consecutive uses. In conclusion, intercalation of molybdate anion into the layered double hydroxide salt proved to be an efficient alternative to support the active species and transform a soluble catalyst into a solid with application in heterogeneous catalysis.

Resumo em Inglês:

Metabolites are known to characterize the functional responses of a cell. Therefore, a quantitative measurement of metabolite profiles can provide insight into the underlying effect of genetic or environmental actions on cell metabolism. It follows then that the study of the metabolite profiles of bivalve mollusks, such as oysters, can be particularly worthwhile in assessing changes in physiology, pharmacology and toxicology that result from their adaptation to changing environments. We have determined the metabolic profiles of three different organ groups in freshwater mussel and oysters by using 1H (proton) and 13C (carbon) NMR (nuclear magnetic resonance) spectroscopy following the infusion of 13C glucose or 13C glycine, respectively. The result shows infused glucose formed glycogen by glycogen synthesis, alanine by glycolysis, and glutamate and aspartate through the Krebs cycle and glycine formed serine by the glycine cleavage system in oysters. Decrease in adenosine triphosphate (ATP), glucogen, putrescine and ornithine were observed in the fasting state freshwater mussel. Our result opens the possibility that organ specific metabolic fingerprints can be established to interpret functional adaptations to environmental and nutritional challenges using NMR spectroscopy.

Resumo em Inglês:

The official method for analyzing N-nitrosoglyphosate (NNG), a relevant impurity, in glyphosate matrix demands complicated instrumentation and operating conditions not available in many laboratories. In this work, we developed a direct, simple, selective and sensitive ion chromatography (IC) method with UV detection for the determination of NNG in samples of technical glyphosate. To separate NNG from the matrix we used an IC anionic column mounted in a high-performance liquid chromatography (HPLC) apparatus equipped with a photo-diode array detector. The system used a high ionic strength eluent. The method was validated, taking into account the following figures of merit: selectivity, linearity, repeatability, intermediate precision, recovery, limit of detection (LOD), and limit of quantification (LOQ). The proposed method is sensitive enough to quantify NNG below the maximum concentration determined by both the Food and Agricultural Organization of the United Nations (FAO) and the Brazilian regulation.

Resumo em Inglês:

The genus Lippia comprises approximately 200 species of herbs, shrubs and small trees, distributed throughout the South and Central America and tropical Africa. The species Lippia gracilis Schauer is an endemic aromatic plant of the Brazilian Northeast normally found in the states of Bahia, Sergipe and Piauí. The traditional communities of Caatinga, a semi-arid region of the Brazilian Northeast, use its leaves to treat throat and mouth infections, cutaneous diseases, ulcers, vagina disorders, acne, Pityriasis alba, dandruff, burns, wounds, sinusitis, bronchitis, nasal congestion, headache, jaundice and paralysis. Considering that the main investigations into the L. gracilis Schauer species are focused on its volatile constituents, in this report, we describe the isolation, by liquid chromatography with diode array detector-solid phase extraction/nuclear magnetic resonance (LC-DAD-SPE/NMR), of five flavonoids besides free and glycosidically bound carvacrol from an infusion of the leaves of a genotype of this species.

Resumo em Inglês:

Binary mixtures of block copolymers E114CL20 and E97P69E97 (F127(®)) were prepared in order to tailor a drug delivery system with synergistic effect, concerning dilution stability and high drug solubility. Both reduction of the critical micelle concentrations (CMC) values and enhance hydrophobic drug solubility in F127/E114CL20 mixtures (30-50 wt.%) were observed by addition of the diblock E114CL20, also reaching the best enhancement of drug solubility for mangiferin and carbamazepine.