Resumo em Inglês:

The use of L-proline derivatives employed in OXA-Michael-Henry tandem reactions has been an efficient method to produce enantiomerically enriched compounds. In this work it was carried out a study of the OXA-Michael-Henry reactions between salicylaldehyde and β-nitrostyrenes, catalyzed by L-proline and its derivatives. The corresponding (R)-3-nitro-2-phenyl-2H-chromenes were obtained in 55% enantiomeric excess (ee, 20 mol% L-proline) and 70% ee (stoichiometric amount) employing Ti(OiPr)4 as Lewis acid. Despite the ee obtained, to the best of our knowledge, this result represents the highest enantioselectivity obtained in this reaction. Therefore, this work demonstrated that it is possible to obtain considerable enantiomeric excesses in OXA-Michael-Henry reactions using L-proline, an inexpensive and accessible amino acid.

Resumo em Inglês:

Different fuels are used in Brazil and there is little knowledge about the presence of organic and inorganic acids in the atmosphere of the Brazilian cities. HNO3, HCl, HCOOH and CH3COOH were sampled in the gas phase using passive samplers and thermodiffusion system, in which the H2SO4 particulate was also sampled, in five sites of Salvador. Ion chromatography analyses showed that the organic and inorganic acids measured contributed on average with 89 and 11%, respectively, to the acidity of the city’s atmosphere. The strong correlations between HCOOH, CH3COOH and HCl with CO and NO2 indicated a common source for these compounds, predominantly from vehicular emissions. H2SO4 showed strong correlations with PM10 (particulate matter 10 µm or less in diameter) and with its precursor SO2; and HNO3 with NO2 and NO precursors. Most of the compounds presented negative correlations with meteorological parameters. Principal component analysis (PCA) and hierarchical cluster analysis (HCA) confirmed these observations. The ratios [HCOOH] / [CH3COOH] varied between 0.69-1.9, typical of urban areas.

Resumo em Inglês:

In order to investigate the anthropogenic and natural sources of metals in the Gulf of Prigi, Indonesia, it was analyzed their metal contents and Pb isotopes of surface seawater together with sediment, grouper fish, mosh, seaweed, soil, and sharp grass for protecting the environmental pollution of the study area. Samples were leached using a microwave digestion technique. Metal (Ca, Fe, Mn, Cu and Pb) concentrations and 206Pb, 207Pb and 208Pb in the leached solutions were analyzed using inductively coupled plasma-mass spectrometry (ICP-MS). The level concentrations of Ca (491436 µg kg–1), Fe (12123 µg kg–1), Mn (37.2 µg kg–1), Cu (84.0 µg kg–1) and Pb (34.5 µg kg-1) in the surface seawater were low compared with those of background seawater levels issued by World Health Organization (WHO). The range of Pb isotope ratios (207Pb / 206Pb = 0.7966-0.9945 and 208Pb / 206Pb = 2.2600-2.8243) in surface seawater was higher in the plotted Pb growth curve suggesting unpolluted Pb reflected by natural sources such as mineral sources or lithogenic from marine sediment.

Resumo em Inglês:

Ocimum gratissimum oil is used for various medicinal, food and cosmetic applications due to its high chemical variability. Local businesses have considered the economic exploitation of this plant. A specimen sampled at São Luís, MA, Brazil, with thymol and derivatives oil, was subjected to seasonal and circadian study, and to antifungal and antioxidant assays. It was possible to observe that the weather conditions showed a direct influence on the oil yield and variation of its constituents, mainly oxygenated monoterpenes and monoterpene hydrocarbons, with the predominance of thymol, γ-terpinene, and p-cymene. Principal component analysis (PCA) was able to justify the oil chemical variability of the seasonal (70%) and circadian (86%) study. Oil displayed inhibition for the fungus Corynespora cassiicola at a concentration above 0.3 µL mL-1, and it showed a more significant activity by comparison to thymol. Using 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical assay, the oil antioxidant activity was about 75% of thymol.

Resumo em Inglês:

The leaf-footed bug, Leptoglossus zonatus (Heteroptera: Coreidae), is mainly found in maize fields in Brazil. In this work, we elucidated and quantified the volatile compounds from nymphs and adults of L. zonatus. The defensive compounds produced by nymphs are aldehydes and oxo-alkenals, with some compounds showing different proportions between instars. For the first time, 5-ethyl-2(5H)-furanone has been identified as a defensive compound for a species of this family. In adults, the alarm pheromone includes hexanal, 1-hexanol, hexanoic acid, hexyl acetate, and octyl acetate. Males and females produce the same compounds, however, hexanal showed a significant difference between sexes. Gas chromatography (GC) analysis of adult aeration extracts revealed male specific compounds, which attactiveness to females was confirmed through olfactometer bioassays. By using a GC-electroantennographic detector (EAD), it was shown that female antenna presented electrophysiological responses to five components ((Z)-β-ocimene, (Z, Z)-allo-ocimene, decanal, α-trans-bergamotene, and (E)-β-farnesene) from male aeration extracts. In this way, we propose that males are responsible for emission of a sex pheromone in this species.

Resumo em Inglês:

The influence of electrostatic and dispersion components of intermolecular interactions on the recognition of carbohydrates by aromatic protein residues is important for many biological processes. Interactions between glucose and galactose and aromatic moieties of tryptophan, phenylalanine and histidine were investigated through 1H nuclear magnetic resonance (NMR) chemical shift perturbation and fully explained by molecular modelling at the density functional theory (DFT) level. According to NMR experiments, aromatic amino acids interact preferably with one face of the carbohydrate and the calculations showed how intermolecular interactions were determinant in explaining the selectivity. Non-covalent interaction surfaces revealed that a CH bond oriented toward the center of the aromatic ring maximized the attractive interaction while minimizing the steric repulsion. Energy decomposition analyses showed that the dispersion component was stronger than the electrostatic component and contributes more when hydrogen bonds are not present in the studied complexes. However, it was the electrostatic component that correlated with the facial preference, especially for the complexes with tryptophan.

Resumo em Inglês:

Rollinia mucosa fruit has generated great interest due to the presence of bioactive compounds, which exhibit promising biological activities. Fingerprinting analytical techniques, chromatographic-diode array detection (DAD), infrared, mass spectrometric, 1H and 13C nuclear magnetic resonance (NMR) spectra, associated with chemometric analysis and mixture design, were used to determine chemical discriminations of sun-exposed and self-shaded leaves of Rollinia mucosa in each of the four seasons. Sunlit leaves in winter presented higher metabolite signals related to the acetogenins, whereas shaded leaves have higher abundances of carbohydrates and terpenes. Sunlit leaves harvested in the summer had the smallest metabolite abundances. Fingerprints confirmed the presence of two acetogenins, annonacin A and annonastatin. Ternary and quaternary mixtures of the statistical mixture design were most effective for revealing important discriminations.

Resumo em Inglês:

The methodology developed in this study through the acquisition of fingerprint chromatograms by liquid chromatography-diode array detector (LC-DAD), aided by principal component analysis, made it possible to assess, in a rational way, the chemical differences between six accessions of Lippia alba and to verify the influence of the method of extraction, the seasonality and the individuality of each accession on chemical composition of its extracts. Among all extracts analyzed against cancer cell lines, eight of them showed to be more promising against a human leukemia cell line (HL-60), displaying cell growth inhibition percentage ranging between 40.0 and 52.0%. In the inhibitory activity assays against acetylcholinesterase enzyme, all extracts showed weak inhibitory effect, with highlight only for six of them, which displayed inhibition ranging between 27.0 and 32.0%.

Resumo em Inglês:

In this paper, Cu-doped carbon quantum dots (Cu-CQDs) were prepared by carrying out thermolysis of Na2[Cu(EDTA)] and hydroxylamine hydrochloride at 300 ºC for 2 h. The as-prepared Cu-CQDs were characterized by UV-Vis, Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The Cu-CQDs exhibited good fluorescence property, high stability, excitation-dependent emission behavior and a quantum yield of 9.8%. More significantly, the synthesized Cu-CQDs were developed for sensing rutin (RT) based on the fluorescence quenching of the prepared Cu-CQDs. A good linear relationship between the fluorescence quenching of Cu-CQDs and different concentrations of RT was obtained in the range of 0.1-15 µg mL-1 with a correlation coefficient of 0.9959. The detection limit was as low as 0.05 µg mL-1 (signal-to-noise ratio, S/N = 3). The possible mechanism of fluorescence quenching was explored, which was proved to be inner filter effect. Importantly, the proposed method was successfully applied in the detection of RT tablet samples and with satisfactory results, showing the practical applications.

Resumo em Inglês:

Hydrocarbons present in saturated fractions of crude oils can be assessed by atmospheric pressure chemical ionization (APCI) using small hydrocarbons as ionizing reagents in a Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR MS). In this work, five paraffin standards of different average molar mass distributions (Mw) were easily ionized by APCI(+)FT-ICR MS using isooctane as the reagent gas. Data of Mw, carbon number and double bond equivalent (DBE) distributions corresponding to linear and cyclic hydrocarbons (HCs) were compared to results obtained from analysis of high temperature gas chromatography with a flame ionization detector (HTGC-FID), comprehensive two-dimensional gas chromatography coupled to mass spectrometry (GC×GC-MS) and 1H and 13C nuclear magnetic resonance (NMR) spectroscopy. APCI(+)FT-ICR MS data showed good agreement with those of analytical techniques. Furthermore, the ability of APCI(+) to assess n-paraffin, even in blends with polyaromatic hydrocarbon molecules such as coronene (Mw = 301 Da) at concentrations from 2.5 to 25 µg mL-1, was demonstrated. The typical MS paraffin profile (containing repeating mass units of 14 Da) was clearly confirmed, being totally suppressed when a concentration of 25 µg mL-1 of coronene was used. This phenomenon was also evidenced in one of two saturated fractions produced using saturates, aromatics and polar (SAP) compound fractionation methodology.

Resumo em Inglês:

Photolytic degradation of fluoxetine (FLX), a medicine commonly known as Prozac®, was evaluated by using different photochemical processes. The ultraviolet/microwave (UV/MW) process showed higher efficiency in all the aspects evaluated in this study. The energy consumption was equivalent to 1.94 × 10-4 kW h mg-1 L (UV/MW), while in the UV process the value was 1.20 × 10-2 kW h mg-1 L. The degradation kinetics were applied to the FLX, with rate constant (k) = 0.15 ± 0.01 min-1 and linear correlation coefficient (R2) = 0.980 for UV, and k = 6.15 ± 0.08 min-1 and R2 = 0.998 for UV/MW. The FLX degradation of 99.16% (UV/MW 5 min) and 98.90% (UV 120 min) were observed, evidencing higher efficiency for the first process. The monitoring of transformation products (TPs) through chromatographic analysis enabled the identification of 9 TPs, proving that for the UV/MW process, the hydroxylated structures are verified in high quantity.

Resumo em Inglês:

Surplus of glycerol production from the biodiesel industry has led to the search for glycerol conversion routes, the most common of which are dehydration and oxidative dehydration. Vanadium and molybdenum oxides were supported on γ-Al2O3 and their properties were analyzed through several characterization techniques, showing that the acidity increases after addition of oxides and that in the catalyst with vanadium and molybdenum there is decrease in the band referring to V5+, responsible for sequential oxidation to CO2. The effect of the metal oxides on catalytic activity and stability during oxidative dehydration of glycerol to acrolein was investigated and correlated with chemical composition, acidity, and textural properties. Moreover, the global reaction, turnover frequency (TOF), and activation energy were determined. Catalyst performance and stability were found to depend on acidity and the supported metal with larger residence times (W/F) favored acrolein formation over COx. In addition, metal oxides decreased catalyst deactivation via coke oxidation.

Resumo em Inglês:

Cagaita is a fruit from Brazilian cerrado, belongs to Myrtaceae family, and has important economic value. This work aimed to determine the total antioxidant capacity (extractable and non-extractable fractions) by different methods and to evaluate the use of paper spray mass spectrometry to obtain fingerprints of cagaita from different regions with the aid of principal components analysis. Cagaitas had higher antioxidant activity than those found in other fruits mentioned in literature, and the non-extractable fraction was 18.90 to 21.05% of the antioxidant capacity. The analysis of paper spray mass spectrometry in positive and negative ionization modes identified several substances, including organic acids, sugars, amino acids and several other classes of phenolic compounds. Analysis of the main components of cagaita samples permitted discrimination of the major constituents such as sugars and different kinds of phenolic compounds. Thus, this study demonstrated that paper spray mass spectrometry is a simple and ultrafast method with minimum sample preparation that allows the analysis of the chemical profile of cagaita.

Resumo em Inglês:

We report a series of functionalized dienes as compounds of great potential in the treatment of Alzheimer’s disease due to their antioxidant activity and ability to inhibit the enzyme acetylcholinesterase. The dienes tested showed high enzymatic inhibition capacity and accentuated antioxidant activity, which are comparable to or higher than the standards tested. Molecular docking studies were performed to confirm the experimental results. We also describe the correlation values between the antioxidant activity and oxidation potentials. Predicted bioactivity scores and quantum studies were also determined.

Resumo em Inglês:

The modification of four extra virgin olive oils from different origins with refined soybean oil (SO), in the proportions of 0, 5, 10, 20 and 30% m/m, was studied using two approaches. First, the induction period (IP) was determined by Rancimat. In the second strategy, ion chromatography was used to quantify the formic and acetic acids, in their carboxylate forms (formate and acetate), present in the water contained in the measurement vessel of the Rancimat device, 21 h after the beginning of the induced oxidation of the samples. The content of the adulterant (SO) was linearly correlated with the IP (mean correlation coefficient (R) = 0.9858) and the concentration of the formate (mean R = 0.9979) and acetate (mean R = 0.9951). Also, it was observed that as the IP decreased and the formic acid and acetic acid concentrations increased, the monounsaturated fatty acids/polyunsaturated fatty acids ratio decreased.

Resumo em Inglês:

Human milk (HM) is extremely important to the baby, containing a varied and balanced range of nutrients fundamental to the ideal development of the newborn. Among these nutrients, HM lipids provide 40-60% of the energy. In HM banks, the creamatocrit method is employed as a quick and solvent-free tool, however, since Folch methodology is considered reference for lipid extraction, this study compared the fatty acid (FA) composition and the lipid profile by gas chromatography with flame ionization detector (GC-FID) and direct infusion by electrospray ionization mass spectrometry (DI-ESI-MS) in pools of different HM phases, obtained from Folch and creamatocrit methods, in order to elucidate which method provides better information about HM lipids. Lipid compositon results by Folch were superior to the results obtained by creamatocrit in HM pools investigated. It means, the lipid profiles of all HM pools were more intense, and the number of FA identified by Folch was also higher in comparison to the creamatocrit method (21 and 6 FAs, respectively). GC-FID analysis in combination with principal component analysis (PCA) divided the methods, confirming a greater contribution of the Folch method. Therefore, Folch methodology revealed an effective lipid extraction in comparison to creamatocrit method.

Resumo em Inglês:

Paper spray ionization (PSI) is a promising analytical tool for direct analysis in mass spectrometry (MS). However, this technique usually uses chromatographic paper, which rarely accomplishes a stable MS signal and could vary with the sample matrix effect. In the present study, the application of graphene oxides (GO) was scrutinized as modifier paper substrate for PSI-MS methods. The developed substrate efficiency was evaluated towards creatinine determination in urine samples. The GO-PSI-MS developed method for creatinine in urine samples showed linearity in the range of 0.1 to 3.4 ppm with R2 = 0.9991. The precision was evaluated and the values were between 1.1 to 6.8% and the accuracy above 96.8%. The limit of quantification (LOQ) and limit of detection (LOD) were 0.05 and 0.17 ppm, respectively. The GO-PSI developed was compared to conventional chromatographic paper for PSI-MS methods, and the results showed that the modified paper with GO bolsters method linearity, precision, and LOQ values.

Resumo em Inglês:

Content uniformity (CU) is a parameter used to ensure the uniformity of the amount of active substances in pharmaceutical preparations. It is often evaluated in the quality control of pharmaceutical dosage forms, and a novel method was proposed for CU determination using thermal infrared enthalpimetry (TIE). Captopril tablets were dissolved in 24-well microplates and the heat released from the reaction of captopril and I2 was monitored with an infrared camera. Some experimental parameters were adjusted, as captopril/I2 ratio, stirring speed and dispensing rate, and the most suitable conditions were 1.00:1.00 (v/v), 250 rpm and 0.57 mL s-1, respectively. Interferences from tablet adjuvants (e.g., starch, cellulose and lactose) were not observed. The results obtained by TIE did not differ statistically (Student’s t-test, p > 0.05) from those from official method (UV spectrophotometry) described in pharmacopeia. The TIE method required 31 and 12 times less reagent and time, respectively. Therefore, the proposed method was suitable for routine analysis and agrees with the requirements of green analytical chemistry.

Resumo em Inglês:

An automated microsystem for sulfite determination in beverages was developed. It presents higher sampling throughput, lower chemical consumption and less waste generation than previous flow methods, while using the same p-rosaniline-formaldehyde-sulfite reaction. The sampling rate, limit of detection (LOD), and relative standard deviation (RSD) were estimated at 130 h-1, 80.0 µg L–1, and < 1.3% (n = 5), respectively. Recoveries ranged from 96.8 to 102.6%.

Resumo em Inglês:

The use of nerve agents, organophosphorus compounds which irreversibly inhibit acetylcholinesterase, in conflicts and terrorism has gained renewed geopolitical status in recent years. As no “universal antidote” has ever been produced, the development of antidotes to reactivate enzyme is clearly warranted. Given the fact that nerve agents are restricted substances, the use of surrogates allows non-qualified laboratories to develop research on novel antidotes. We herein present an alternative and efficient synthesis of NEMP, O-(4-nitrophenyl) O-ethyl methylphosphonate, a venomous agent X (VX) surrogate, and Ellman’s test procedures for inhibition and reactivation of Electrophorus eel acetylcholinesterase involving the NEMP-generated adduct.

Resumo em Inglês:

A new flavonol triglycoside, named kaempferol-3-O-β-D-glucopyranosyl-(1→4)-α-L-rhamnopyranosyl-(1→6)-β-D-glucopyranoside, was isolated from flowers of Aristolochia trulliformis (Aristolochiaceae) together with 15 known compounds, including six flavonoids and four lignans. The structures of the compounds were determined by spectroscopic analyses, including 1D and 2D nuclear magnetic resonance (NMR) techniques and high-resolution mass spectrometry (HRMS).

Resumo em Inglês:

Natural sources with high antioxidant capacity represent an interesting potential to prevent or minimize the oxidative stress that causes many chronic diseases. The antioxidant capacity of red fruits (strawberry and cherry) was evaluated by miniaturized spectrophotometric methods 2,2’-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS), 2,2-diphenyl-1-picrylhydrazyl (DPPH) and nitroblue tetrazolium (NBT). ABTS and DPPH colorimetric methods are based on the ability of antioxidants to scavenge synthetic free radicals produced in vitro, which have a different chemical structure from the natural reactive oxygen species generated in the human body. In this respect, the NBT method stands up because it is based on O2•– scavenging which is generated in vitro by enzymatic reaction systems. The spectrophotometric assays adapted on microtiter plates allowed a rapid, inexpensive and simultaneous analysis. Larger amounts of lipophilic and hydrophilic antioxidants were obtained from strawberry fruit, which showed the lowest 50% signal inhibition concentration (IC50) values. The fruit analyzed showed promising sources of bioactive compounds with high antioxidant properties.