Resumo em Inglês:

The Parnaíba Basin covers an area of 665,888 km2 between the northern and northeastern regions of Brazil. It is completely made up of siliciclastic sedimentary and volcanic rocks with ages varying between the Silurian and the Cretaceous. Among the formations of the Basin, the Tianguá Formation is considered a potential source rock. However, there are few geochemical and/or geological studies and no research work on the molecular parameters of the organic matter (OM) present in its outcropping rocks (OR). Thus, the objective of the present work is to characterize the OM, concerning the depositional paleoenvironment and the degree of thermal evolution, through molecular parameters and OM content. The OM was extracted using the Soxhlet system, chromatographed by classical methods, and analyzed using GC-MS and GC-MS/MS. The samples exhibited low total organic carbon values (TOC < 1) and the molecular parameters of saturated and aromatic hydrocarbons suggested a marine depositional environment, with algae, bacteria, and terrestrial plants input. The C30 biomarkers (24-n-propylcholestane), identified using synthetic standards and usually associated with the Chrysophyte algae, corroborated the marine origin of the depositional environment. In addition, some molecular parameters suggested little thermal evolution.

Resumo em Inglês:

In this work, a recyclable and sensitive fluorescent nanoprobe, RhoB@ZIF-8 composite, has been designed and successfully synthesized by encapsulating rhodamine B (abbreviated as RhoB) into the cavities of zeolitic imidazolate framework-8 (ZIF-8) metal-organic frameworks (MOFs) through a facile one-pot method under mild conditions. The RhoB@ZIF-8 composite exhibited an emission band at 589 nm with fluorescent quantum yield of 19.8%. Since there was an efficient overlap between the absorption of malachite green (MG) and the fluorescence spectra (excitation and emission bands) of RhoB@ZIF-8 composite, the fluorescence intensity decreased sharply after MG was added. The fluorescence quenching was linear with the concentration of MG in the range of 0 to 13.0 μM with a low limit of detection (LOD) of 0.089 μM. Remarkably, this proposed sensing system has good performances including high specificity, good stability and recyclability. Finally, this fluorescent probe was successfully applied to the detection of MG in aquaculture water and fish tissue samples, revealing its potential practicability. This work will provide us a new research platform for MG sensing.

Resumo em Inglês:

Reducing non-specific adsorption of proteins on the surface of magnetic nanoparticles (MNPs) is becoming increasingly important. In this paper, we proposed a novel surface modification procedure by grafting hyperbranched polyglycerol (HPG) onto the surface of MNPs (Fe3O4@SiO2@MAA), in which lots of hydroxyl groups from HPG not only provide the hydrates sheath to prevent non-specific adsorption of proteins, but also react with succinic anhydride to generate carboxyl groups that serve as active sites to specifically bind proteins. The protein adsorption experiments showed that the non-specific adsorption (0.07 μg mg-1) was reduced to 4.58% of that before modification. It also showed that the antigen binding capacity was 9.7 times higher than the original when detecting cardiac troponin I (cTnI) in human plasma samples, which indicated that the final synthesized MNPs had great application prospects in bio-separation and bioanalysis.

Resumo em Inglês:

Volatile Organic Compounds (VOCs) are air pollutants emitted from different sources, mainly by industries and motor vehicles. The evaluation of the emission of these compounds into the atmosphere should be done systematically and with a varied class of compounds. The large number of data generated during the monitoring of these VOCs requires the use of multivariate data tools to interpret the results. In this sense, this work aimed to monitor 10 aromatic VOCs present in the atmosphere of the largest cities in the Norte Fluminense (Campos dos Goytacazes) and Noroeste Fluminense (Itaperuna) regions. The VOCs were actively sampled and analyzed by gas chromatography with mass spectrometry detection after thermal desorption. After treatment of analytical results, it was observed that in both cities there is influence of vehicular emissions. In the city of Itaperuna, due to the relief and lower dispersion of contaminants, there is a higher occurrence of photochemical reactions. The exploratory analysis of the data allowed identifying the variables that were more significant and correlating these variables with the main sources of emission of the compounds. This is the first study of VOCs evaluation in Campos dos Goytacazes and Itaperuna, demonstrating the relevance of this research for understanding the behavior of VOCs in these cities, which have different reliefs and high traffic of cars and trucks in the studied sites.

Resumo em Inglês:

In the present work, dried aerial parts of Baccharis ligustrina (Asteraceae) were subjected to microwave assisted extraction (MAE) using aqueous solution of 1-butyl-3-methylimidazolium bromide (BMImBr) and the obtained extract was successively partitioned using hexane and EtOAc. Using reduced amounts of extracts and efficient chromatographic steps, four acyl C6C3 derivatives (n-hexacosyl ferulate, n-hexacosyl, n-octacosyl, and n-triacontyl p-coumarates) were obtained from hexane phase whereas two C6C3 acids (ferulic and p-coumaric) were obtained from EtOAc phase. Isolated phenylpropanoids were evaluated against amastigote forms of parasite Trypanosoma cruzi. As result, it was observed that p-coumaric and ferulic acids were inactives whereas alkyl derivatives displayed EC50 values of 6.5 µmol L-1 (n-octacosyl p-coumarate), 9.3 µmol L-1 (n-triacontyl p-coumarate), 15.7 µmol L-1 (n-hexacosyl p-coumarate), and 32.2 µmol L-1 (n-hexacosyl ferulate). All tested compounds displayed reduced toxicity against NCTC cells (CC50 > 200 mmol L-1).

Resumo em Inglês:

The development of new strategies for the functionalization of the historically inert C—H bond arises as an excellent way to create new carbon—carbon and carbon— heteroatom bonds. With increasingly chemo- and site-selective methods that enables the late-stage functionalization of C—H bonds, the modification of specific sites in natural products and pharmaceuticals without altering their scaffold emerges as a powerful means for the diversification of complex molecules. In this review, we will introduce concepts of late-stage modifications, the use of C—H bond functionalization to forge new carbon—carbon and carbon—heteroatom bonds using metal catalysis and photochemistry in simple examples and their applications in natural products and pharmaceuticals. The aim of the review is to update and display to the reader the contributions and implications of this methodology to organic synthesis.

Resumo em Inglês:

The mangosteen (Garcinia mangostana, Linn.) is a tropical fruit cultivated in the tropical forests of Southeast Asian countries. It is recognized as the queen of fruits due to its unique color, aroma, and flavor. It has been used for centuries in Southeastern Asian traditional medicine for the treatment of various diseases. Many functional molecules with high medicinal value are obtained from the pericarp of mangosteen fruit, whose major constituent is xanthone α-mangostin. Several studies have been carried out over the last decades to further investigate and understand the pharmacological properties associated with the plant and its main chemical constituents, belonging to the class of xanthones. In addition, numerous in vitro and in vivo studies related to mangosteen have been published, indicating its importance and its potential application in medicinal chemistry. Prenylated xanthones, which include α-mangostin, are secondary metabolites particularly common in plants belonging to the Clusiaceae family. These substances have been intensively investigated for their potential as biologically active agents. This article describes a critical analysis of published data related to the properties of α-mangostin, aiming to provide a more detailed view of its potential as a chemotherapeutic agent for the prevention and treatment of infectious diseases.

Resumo em Inglês:

An inert atmosphere is, in some cases, important for the performing of experiments where substances are toxic and/or sensitive to oxygen. However, the high cost and accessibility of an equipment to work under these conditions, results in the fact that most laboratories do not have this kind of equipment. In this paper, we present a simple and efficient project to build a cheap glove box for processes that require an inert atmosphere. The proposed glove box is made using medium density fiberboard (MDF), an acrylic lid, hinges, air valves, PVC gloves and other materials that can be found easily in local stores or on the internet. Tests to verify the quality of the nitrogen atmosphere were performed using the lighter test and niobium pentachloride (NbCl5), which is a moisture/ oxygen sensitive material. The results demonstrated that the equipment is able to maintain an inert atmosphere for several hours, does not permit lighter to function and maintains the NbCl5 stable.

Resumo em Inglês:

Chemometrics is a subfield of chemistry that emerged from advances in analytical instrumentation and computing. When seeking to solve chemical problems that depend on many concomitants experimental variables, chemometrics can be employed in order to extract as much information as possible in the least possible number of experiments. In addition, it is possible to evaluate the important effects and interactions among the variables to understand the processes being monitored in each system. In this sense, this article aimed to develop a didactic experiment of caffeine extraction using an espresso machine, applying the 25-1 fractional factorial design. The variables studied were temperature (75 and 78 °C), pressure (2 and 15 bar), granulation (bean and ground), type of coffee (special and traditional) and period of the day (morning and afternoon) to obtain maximum extraction of caffeine. The coffee extracts obtained were analyzed using UV-Vis molecular absorption spectrophotometry. The developed experiment showed the potential to spread the application of chemometrics in the academic environment and to facilitate the teaching of fractional factorial design.

Resumo em Inglês:

This work aims to compare the construction of magnification devices. Details of the construction and use of microscopes based on webcam and smartphone are presented, using software for image processing. It is also presented the construction of microscopes using drops of different liquids as magnifying lens, a compound microscope, and a water-drop projector. Magnified images obtained with each device are presented, and the different microscopes are compared. The results obtained from the use of these alternative instruments confirm that alternative microscopes are instruments of easy reproducibility, enabling the amplification of samples for a more detailed observation of the object of interest.

Resumo em Inglês:

The study of History of Education is very important to teacher education because it allows reflections and greater criticality about their own teaching practice and professional condition. The purpose of this research was to identify similarities between the curriculum of Chemistry courses of University of Coimbra (UC), National School of Chemistry (ENQ) and School of Engineering of Porto Alegre (EEPA) at the beginning of the 20th century seeking to identify possible influences of UC in the structuring and curriculum of the first Brazilian higher education Chemistry courses. The results showed more similarities regarding the structure between UC and ENQ, while there were greater correspondences in the curricular activities between UC and EEPA. Finally, it was not possible to identify confluences in the curriculums of the courses over the decades since there was a divergence between the models of organization of the higher education in the countries under study.

Resumo em Inglês:

The professional practice of chemist is defined by Ordinary Resolution nº 1,511 of 1975, edited by the Federal Council of Chemistry. This legislation is outdated and not in line with the National Curricular Guidelines for chemistry courses, approved by the National Council of Education in 2001. This situation has greatly hampered the training of future chemistry professional and the modernization of undergraduate courses and must be urgently corrected by those responsible for formulating the legislation that defines the chemistry courses. Thus, we understand that the time has come for the Federal Council of Chemistry, Scientific Societies and Universities to work together to solve this problem, modernizing the legislation that defines the attributions of the chemistry professionals and defining the necessary profile for their professional practice in the XXI century.