Resumo em Inglês:

Although Quercetin absorbs in the UVA/UVB electromagnetic region, it is limited for applications as a UV filter due to its low lipophilicity and capacity to penetrate the epidermis. In order to overcome this limitation, we synthetized and evaluated the photo protective properties of a derivative obtained from Quercetin. The derivative was prepared by alkylation of Quercetin with iodoethane and characterized by IR and NMR spectroscopy. The in vitro Solar Protection Factor was determined by the Mansur method and the cytotoxicity was evaluated using hepatocellular cell (Hep G2) cells. Finally, Quercetin and the corresponding derivative were incorporated in nanoemulsions. Nanoemulsions with particles sizes between 53 and 73 nm were obtained, and polydispersity indexes were around 0.1, indicating good homogeneity of the nanoemulsion particles. The cell viability study for the Quercetin derivative indicated a very low cytotoxicity profile. The chemical modification of Quercetin resulted in a promising compound with improved properties desirable for skin penetration and incorporation into sunscreen formulations.

Resumo em Inglês:

Various species of Paris have been used in treatments for their antitumor, antimicrobial, hemostatic, anthelmintic and immune-stimulating properties, among others. The bioactive markers of these plants including paris saponins I (PSI), paris saponins II (PSII), paris saponins VI (PSVI) and paris saponins VII (PSVII) are responsible for inhibiting nasopharyngeal carcinoma epithelial cell and ethanol-induced gastric lesions. This paper intends to comprehensively characterize the distribution of bioactive markers and illustrate the relationship between chemical profile and Paris spp.. A targeted quantitative analysis by ultra high performance liquid chromatography (UHPLC) was established for the simultaneous separation and determination of PSI, PSII, PSVI and PSVII. Non-targeted analysis based on Fourier transform infrared (FT-IR) spectroscopy, with the aid of partial least squares discriminant analysis (PLS-DA), was also performed. In addition, similarity analysis combining UHPLC and FT-IR spectroscopy were employed to evaluate Paris of different species and geographical origins. Quantitative analysis indicated that the content of saponins varied markedly, and the average total saponins of Paris axialis (PA) of a specific region (Baoshan) was higher than the other species. In addition, total saponins of P. polyphylla var. yunnanensis (PPY) collected from Xishuangbanna was higher than the same species of other regions. Non-targeted analysis indicated that PA was different from other species and PPY in the Baoshan differed from other regions. The results indicate that comprehensive analyses for geographical origin discrimination of herbal medicines are expected to be employed in further investigations.

Resumo em Inglês:

Fifty-two samples of street cocaine seized in the state of Rio de Janeiro, from May 2016 to April 2017, were evaluated according to their purity, presence of inorganic and sugar diluents and concentration of pharmacologically active adulterants. Cocaine contents, as well as the adulterants caffeine, lidocaine and phenacetin, were evaluated by gas chromatography coupled with mass spectrometry. The samples were screened by Raman spectroscopy for the presence of inorganic diluents and carbohydrates. The main diluents were calcium carbonate and sodium bicarbonate, which were found in 93% and 71% of the cocaine hydrochloride samples, respectively. Caffeine was found in 91% of the cocaine hydrochloride samples, while phenacetin was found in all freebase cocaine samples. Freebase cocaine samples were majorly composed of pharmacological active compounds (adulterants), unlike cocaine hydrochloride samples, which were majorly composed of inorganic compounds (diluents). It could be observed, by Raman Spectroscopy associated to multivariate analysis, similarities on cocaine hydrochloride composition according to certain criminal gangs. The percentage of pharmacological active compounds varied significantly on the analyzed samples, showing that these adulterants are indiscriminately added to street cocaine, what may increase consumers’ health risks.

Resumo em Inglês:

The oil from the macaúba (Acrocomia aculeata) fruit, a native palm in Brazil, has a real potential for the industrial production of biodiesel. This report describes an experimental work devoted to monitor the chemical behavior of the fatty acid methyl esters from oil of the macaúba fruit kernel and the leaching of metal elements into the biodiesel put in contact with the ASTM A283 grade C and API X65 carbon steels, used to build fuel storage tanks and biodiesel pipelines. The mean values of esters contents points that the analytical precision from atomic absorption measurements was not enough to support a statistically reliable interpretation of the chemical leaching of metals into the biodiesel; a more accurate set of data must be obtained with more sensitive chemical analytical techniques. From the Mössbauer data, the surface of the non - galvanized steels in contact with this biodiesel for up to 105 days tend to be somehow protected against most oxidative reactions even in direct contact with air, although few amount magnetite (Fe3O4) was detected.

Resumo em Inglês:

This work details the chemical characterization of four NiMo/Al2O3 hydroprocessing generation catalysts (1979-1986, 1993-1998, 2003-2008 and 2008-2011) employed to perform hydrodesulfurization (HDS) of diesel fractions in the same hydrotreater of a Brazilian refinery. The basic differences are the quality of the feedstocks and the HDS experimental conditions. Samples were characterized by X-ray fluorescence, X-ray diffraction, 13C CP-MAS NMR, elemental analysis, loss of volatiles, specific surface area and average pore volume. The amount and variety of foreign elements deposited on the catalyst increased in the most recent generations due to the higher amounts of impurities in the processed feedstocks. Coke became more aromatic and loss of textural properties was more prominent in these samples as expected from the more drastic HDS conditions and the quality of the crude diesel. On the other hand, loss of volatiles was lower due to the low carbon content, partial oxidation of sulfur to sulfate species and oxidation of some elements deposited on the catalyst. Coke tended to ignite as it became more aromatic. For this reason, leaching of decoked samples from the most recent generations by sulfuric acid presented very low yields due to the formation of refractory oxides that are insoluble in the leachant.

Resumo em Inglês:

Colletotrichum gloeosporioides biomass was submitted to ethanolic extraction (78 ºC, 12 h) to remove low molecular weight compounds followed by hot aqueous extraction (100 ºC, 4 h, 4x) to obtain polysaccharides. Consecutive freezing/thawing treatments of the aqueous extract yielded a soluble fraction in cold water that was separated on five components (PI to PV) by gel exclusion chromatography on Sepharose CL-6B. The PIV was homogeneous on HPSEC/RID, with apparent MW of 2.8 x 104 g mol-1, Mw/Mn 1.17, 100% of total sugar. The PIV was composed by galactose (61%), glucose (34%) and mannose (5%). 1H and 13C NMR analysis mono- and two-dimensional, homo- (COSY) and heteronuclear (HSQC and HMBC) showed that PIV is a heteropolysacharide with a main chain constituted by β-D-galactofuranosidic units (1→5) and (1→6) linked with some of the β-D-galactofuranosidic (1→6) units substituted in O-3 by α-D-glucopiranosidic residues. Cytotoxic assays (MTT) indicated that the viability of CHO-K1 cells, when exposed to different heteropolysaccharide concentrations, did not show significant differences when compared to the viability of the negative control (CN), in the experimental times of 24 and 48 hours. These results suggest the possibility of new cytotoxic assays in other normal cell lines as well as in tumor cells.

Resumo em Inglês:

A novel [FeII2L3]4+ metallo-organic helicate results from subcomponent self-assembly of a C3-symmetric triamine (4,4',4''- (1,3,5-triazine-2,4,6-triyl) trianiline), octahedral iron(II) and 2-formyl pyridine in CH3CN solution. The constitution of this supramolecular helicate was confirmed by ESI-MS and 1H NMR spectra. Different planar aromatic guests were selected to investigate host-guest interactions by shifts of 1H NMR signals. The results show that electron-rich aromatic molecules with matched size and symmetry, such as pyrene, are subject to be bound with the outstretched arms of the helicate ligand via aromatic p–p interactions.

Resumo em Inglês:

The objective of this investigation was to identify and quantify the presence of Bisphenol-A (BPA) in raw and treated leachates with the Fenton-adsorption process. BPA is used as a monomer to produce epoxy resins and it is a compound classified as endocrine disruptor. For this reason, it is important to quantify its presence in effluents that will be disposed to the environment to avoid damage to human health and other organisms. The Fenton-adsorption process consisted in the implementation of an advanced oxidation using H2O2 and FeSO4 applied to the raw leachate and subsequently the application of the adsorption process through a column packed with activated carbon. The quantification of BPA was carried out by gas chromatography coupled to mass spectrometry, using liquid-liquid and liquid-solid extraction methods. A recovery percentage study was carried out to validate the extraction methods. Finally, it was found that the leached evaluated contained >12 mg L-1 and at the end of the treatment its concentration was <0.0174 mg L-1.

Resumo em Inglês:

In the last two decades, enantioselective organocatalysis has established itself as one of the three pillars of asymmetric catalysis. The rapid growth in the area is due to the rationalization of organocatalysis based on the generic modes of catalyst activation, being applied to several types of reactions, in a rather generic and predictable way and providing high enantioselectivities. This tutorial review presents the evolution of this area through a brief discussion on all generic modes of activation previously systematized in the literature: activation via enamine, iminium ion, hydrogen-bonding, counterion, SOMO, photoredox, carbene and phase-transfer, and the recent advances in the area.

Resumo em Inglês:

The determination of particle size distribution is an important parameter for controlling industrial processes, particularly in the field of pharmaceuticals. It is also an important parameter for characterizing nanoparticles. The best technique for determining particle size distribution is scanning electron microscopy. The process of counting particles is typically performed manually, which requires both more time and a higher standard deviation than automatic methods. This study shows the results of a particle counting procedure that relies on a fully automated method that was found to improve the reproducibility of the measurement. The effect on the diameter of near-spherical polymer nanospheres between 20 and 100 nm (mean of 60 nm) when samples were coated by a conducting layer (such as gold or carbon) was also evaluated. The images were collected using a field emission scanning electron microscope and then processed using the ImageJ program. Results showed that the method proposed in this work produces mean diameter values in accordance with NIST-traceable near-spherical polymer nanospheres for the sample without coating. The study also revealed two main effects of the conductive coating: changes to topography and an increase in mean particle diameter.

Resumo em Inglês:

This work presents an experiment done for chemistry students about the effect of the nature of the electrolyte and the nature of the interface on the hydrogen evolution reaction by electrolysis. Two techniques are suggested: method A - two identical copper electrodes in a direct current circuit and method B - three different electrodes in a dc potentiostatic circuit, with copper electrode (working), platinum electrode (counter) and silver-silver chloride-KCl sat electrode (reference). The hydrogen evolution was observed using the A technique by increasing potentials between the two electrodes and the visual observation of the gas production at the cathode. The results showed “semi-quantitative” effect of the pH on the hydrogen evolution. It was observed a larger potential difference in alkaline medium than in acid medium. The results obtained with the B technique from polarization curves showed quantitatively the thermodynamic effect of the pH in addition to the least catalytic effect of copper presented in alkaline medium when compared to copper in acid medium for hydrogen evolution. The technique A can be used in technical courses, high school and general chemistry class for under graduate students. The technique B is appropriate for under graduate electrochemistry class and graduate students.

Resumo em Inglês:

Collective authorship or a text written by more than one person in a computer-based environment can bring significant benefits to chemistry teaching, mainly concerning flexibilizing forms of interaction among those involved and collaborative construction of knowledge. This work investigates collective authorship activities based on constructing argumentative texts in groups with the participation of undergraduate chemistry students. In the activity, those involved, divided into groups, followed the textual production process aiming to present a joint solution for case studies. It was possible to understand aspects of collective work in the authorship process in question regarding collaboration and cooperation based on two perspectives considered crucial for collaborative writing: conditions offered by the electronic platform called eduqui.info, and in which contexts these possibilities were present in the writing process; and the organisational aspects of the activity. Overall, groups chose to collaborate more than cooperate. In other words, data shows that most of the students worked collaboratively in groups.

Resumo em Inglês:

United Nations elected 2019 a year devoted to the Periodic Table of the Elements, in deference to the original contribution by Dmitri Ivanovich Mendeleev in 1869. Since then, the impact of the Periodic Table in Science has been tremendous, becoming an icon today as the Chemistry Portal, leading to a better acquaintance of the chemical elements. In this article, modern aspects of the Periodic Table of the Elements are presented, complementing an existing historical presentation in this Journal, with special emphasis on the quantum distribution models and on the remarkable role of the elements in Science and Nanotechnology.