Resumo em Inglês:

The increasing number of antibiotic resistant microorganisms requires the development of new drugs. In this context, natural cadiolides are promising leads as they present potent antimicrobial activity and low cytotoxicity. In this work we report the synthesis of 21 new cadiolide analogues. The synthesis involved a Diels−Alder cycloaddition/ cycloreversion reaction between an oxazole and different ynones, affording four intermediate butenolides (14a-d) in 61-81% yield. These intermediates were subjected to a vinylogous Knoevenagel condensation, followed by demethylation of the methoxylated compounds, affording all 21 analogues in good yields. The antibiotic activity of all compounds was evaluated against a panel of five microorganisms. The bioassays on the microbial growth showed that the cadiolides are more active for Gram-positive than Gram-negative bacteria, and have low activity against the fungus C. albicans. The most active compounds (14b, 15b, 15c and 16e) were effective against S. aureus showing IC50 in the range of 1.8-6.0 µg mL-1. The results also indicated that the nature and position of substituent groups on the aromatic moieties have some effect on the activities.

Resumo em Inglês:

Pouteria sapota is a tropical fruit that is commonly found in central and north part of South America where is widely consumed by its biofunctional properties. The aroma active volatile compounds of Pouteria sapota fruit were studied by using the molecular sensory approach, which includes a SAFE (Solvent Assisted Flavor Evaporation) distillation to get a volatile extract that resembles the fruit aroma, and the combination of GC-O (Gas Chromatography coupled to Olfactometry) with GC-MS analyses to identify odour-active compounds. By AEDA (Aroma Extract Dilution Analysis), β-damascenone, furaneol, linalool, (Z)-3-hexenal, and benzaldehyde, were identified as key aroma compounds in this fruit.

Resumo em Inglês:

Estuaries are major areas of organic matter (OM) deposition, playing an important role in the global carbon cycle. The Itapicuru's river estuary (IRE) is in the North Coast of Bahia (Brazil), in na Environmental Protected Area. Although it presents preserved conditions, some environmental changes caused by human activities can be observed. This study evaluated the anthropogenic impacts importance in concentrations/sources of OM deposited in IRE. n-Alkanes and stable isotopes (δ13C and δ15N) were analyzed in a sediment core collected in the studied region. Total n-alkanes (n-C15 to n-C35), TOC and TN concentrations varied from 1,333 to 7,384 ng g-1, 0.65% to 2.51% and 0.07% to 0.13%, respectively. Values of δ13C and δ15N ranged from -28.8‰ to -24.3‰, -6.23‰ to 1.87‰, respectively. By the means of the isotopic composition and the selected n-alkanes diagnostic ratios values (Productivity aquatic index; Carbon Preference Index; Average Chain Length and Alkane index), the main OM sources for IRE were determined as C3 terrestrial plants. This area is covered by mangrove/riparian vegetation, which mainly species have this photosynthetic pathway. Temporal changes in deposited OM occurred due natural and anthropogenic processes, such urban growth in the IRE upstream region.

Resumo em Inglês:

In 2016, Brazil emitted 18.25 Tg of methane. Some of these emissions occur through continental aquatic ecosystems, locations of fate and accumulation of organic and inorganic matter. Thus, the aim of this study is to evaluate the origin of organic matter in Rodrigo de Freitas Lagoon, an eutrophic, coastal and chocked lagoon in Rio de Janeiro, Brazil, through the determination of n-alkanes and sterols compounds in the upper two centimeters of sediment and compare these data with methane ebullitive flux. The concentrations of n-alkanes varied between 2.43 and 25.82 µg g-1. C29 was predominant compound in most sites, but also with important petrogenic source evidenced by the occurrence of Unresolved Complex Misture. The total concentration of sterols ranged from 2.76 to 56.01 µg g-1. β-sitostanol was the most abundant compound and coprostanol was the most relevant at the sites under influence of domestic effluents. CH4 ebullitive flux averaged 199 mg m-2 d-1 in the dry period and 9.3 mg m-2 d-1 during the wet season. We conclude that the organic matter reaching Rodrigo de Freitas Lagoon through the rivers discharge added or enriched with irregular sewage input and petroleum derivates are the main source of eutrophication and generate higher methane emissions to the atmosphere.

Resumo em Inglês:

In the present work, the chemical reactivity of indaziflam N-[(1R,2S)-2,3-dihydro-2,6-dimethyl-1H-inden-1 yl]-6-[(1R)-1-16 fluoroethyl]-1,3,5-triazine-2,4-diamine so called indaziflam (IND) and its metabolites: triazine indanone (ITI), indaziflam carboxylic acid (ICA) and fluoroethyldiaminotriazine (FDAT) was analyzed. The calculations were performed at the X/6 311++G(2d,2p) (where X=B3LYP, M06, M06L and wB97XD) level of theory, in the aqueous phase. The results indicate that ITI is the more reactive followed by ICA, IND and FDAT. The distribution of the active sites was determined evaluating the Fukui function employing the frozen core and finite difference approximations. For electrophilic attacks, IND shows the more reactive zone on the benzene ring, ITI and ICA on the nitrogen atom in the central section and FDAT on its nitrogen atoms. The more nucleophilic sites for IND are observed on the carbon atoms of triazine, on the carbonyl group for ITI, on the carboxylic group for ICA, and on the nitrogen atoms of triazine for FDAT. For free radical attacks case, the more reactive sites for IND are on the benzene and triazine rings, on the carbonyl group, nitrogen of the central section, and nitrogen atoms of triazine, for ITI, carboxylic group for ICA, and on the nitrogen atoms of triazine ring for FDAT.

Resumo em Inglês:

There are few methods to obtain uniform and well dispersed cuprous oxide nanoparticles, which limits its application widely. In this research, an improved method to prepare nanoparticles was introduced. Cuprous oxides were prepared by the reduction of cupric nitrate, with hydrazine hydrate as a reductant in the presence of glucose. The nanoparticles formed have the characteristics of small particle size and uniform distribution. The crystalline structure and morphological characteristics were analyzed by XRD and TEM respectively. The result showed they were pure sphere polycrystal. The particle size is about 9nm. Subsequently, the antifouling activity was tested in detail through comparative experiments. The results indicated that the effective concentration of nanoparticles was obviously lower than ordinary cuprous oxide.

Resumo em Inglês:

Amino sugars are chemical compounds that have a sugar backbone, in which one of the hydroxyl groups is replaced by an amino group. Derivatives of amine-containing sugars, such as N-acetylglucosamine, are also considered amino sugars. The synthetic introduction of amino functionalities in a regio- and stereoselective manner ontosugar scaffolds represents a substantial challenge. Most of the modern methods for the preparation of 1-, 2- and 3-amino sugars are those starting from glycals, 2,3-unsaturated O-glycosides epoxy-sugars, keto-sugars among others. This review summarizes recente developments in the current state of knowledge concerning the occurrence, biosynthesis, synthesis and application of amino sugars.

Resumo em Inglês:

Heterostructured semiconductors are materials with unique features formed by combination of two or more semiconductors with suitable interface between them. The study of the heterostructures aim the development of physico-chemical and photocatalytic properties higher than their isolated phases, which makes it possible to obtain higher efficiency and lower cost in several technological processes. Recently the heterostructured materials have been extensively used in the development of alternative technologies either for environmental pollution control or for renewable energy production, among other applications. However, the obtaining of a heterostructure with suitable features is not trivial. In this way, this review article presents a broad discussion about methods of obtaining heterostructures formed by semiconductors and their applications in the photochemical processes, mainly in the environmental field. It will be addressed the use of the heterostructures in photocatalytic application for the organic pollutants degradation, heavy metals removal, the inactivation of pathogenic microorganisms, beyond of the volatile organic compounds (VOC’s) photooxidation and the photocatalytic abatement of nitrogen oxide (NOx) in gaseous phase. Finally, a discussion about the carbon dioxide (CO2) photoreduction and hydrogen (H2) production focusing mainly in the chemical energy production will be presented.

Resumo em Inglês:

Determination of two drugs of abuse in saliva has been performed by Paper Spray Ionization Mass Spectrometry (PSI-MS) using a Molecularly Imprinted Polymer (MIP) coated paper as substrate. The method has been optimized for quantification of 3,4-methylenedioxy- N-methylamphetamine (MDMA) and methamphetamine, 3,4-methylenedioxyamphetamine (MDA) from synthetic saliva samples. Rapid analysis (~ 1 min) of designer drugs in saliva is demonstrated using MIP-PSI-MS. Both precursor ions of MDMA and MDA were confirmed by tandem mass spectrometry (MS/MS) experiments by elucidating the fragmentation patterns formed via collisioninduced dissociation (CID). The MIP-PSI-MS method showed greater selectivity for MDMA and MDA in comparison with other analytes. Signal intensity ratios of the most important transitions for MDMA (194 →163) and MDA (180 →163) were found linear (R > 0,99) in the range 25-500 µg L-1. The LOD and LOQ for MDMA were 1.11 µg L-1 and 18.73 µg L-1, respectively, and for MDA were 3.42 µg L-1 and 21.66 µg L-1, respectively. The precision and accuracy values were determined below 4%, and the recoveries about 100%, without pre-concentration/enrichment or separation steps. The MIP-PSI-MS method displays the potential for rapid screening for selective quantitative determination of illicit drugs in saliva samples.

Resumo em Inglês:

The objective of this work was to exclusively improve the management of wastes constituted mainly by organic solvents, due to the opportunities for improvements in the processing of such substances in the institution where the studies were realized. By means of the tests carried out in the distillation system using acetone as a reference, advantages and disadvantages were found with increasing/decreasing the temperature used in the process. From the use of gas chromatography, it was possible to obtain a more precise control of the quality of the recovered product and also to verify the high efficiency of the distillation process in the separation of the solvent from the other contaminants present in the waste. And in terms of comparison of treatments, distillation proved to be environmentally more sustainable and about 8 times more economical than incineration.

Resumo em Inglês:

In this paper, from the experiences of the Collective Ciata, we seek to elucidate theoreticalmethodological aspects that can establish the teaching of Chemistry for education for ethnic-racial relations and the implementation of law 10.639/2003. This research was based on the research-action technique. The recording of the interventions was done followed by transcription and analysis according to the theoretical reference of the analysis of the conversation. Our results show that racism is present in the classroom, therefore, also in Chemistry class. The teacher deals with the real school and must be trained to act in it. It is possible to promote curricular changes in favor of black populations by designing a curriculum that contemplates the ethnic-racial diversity of Brazilian society. Our results showed that it is possible to discuss in a Chemistry class subjects related to the proposals of the mentioned law, as well as, to approach concepts of related chemistry. For this purpose, knowledge was mobilized that were not present in the curriculum of the degree in Chemistry and, therefore, demanded training in service through the group of studies instituted by the Collective Ciata.

Resumo em Inglês:

Proclaimed by UNESCO the International Year of the Periodic Table of Chemical Elements in 2019 (IYPT 2019) will commemorate a remarkable series of important milestones in the history of the periodic table of chemical elements. The periodic table is a valuable instrument for chemistry teaching and their study is important in the development of key chemical concepts. In this sense, this paper aims to present a systematic review of the literature on the productions involving the periodic table in the chemistry teaching, sought answer how the periodic table has been used in the chemistry teaching and what didactic strategies used. For this, a systematic review was carried out in six chemistry journals (with papers in the area of Chemical Education) in the period 2009-2018. During the review, we found four categories (level of education, approach, strategy, didactic/pedagogical resource). The results show that of the 28 articles analyzed, 40% of the publications used didactic/pedagogical approaches. Furthermore, it was possible to observe that ludicity (43%), bibliographic survey (25%) and didactic sequences (18%) represented the strategies most used in these articles. Finally, was evidence that card games, board games, and digital games are the most used didactic/pedagogical resources in the journals’ publications.