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Química Nova, Volume: 45, Número: 2, Publicado: 2022
  • Perspectivas para 2022 Editorial

    Machado, Giovanna; David, Jorge M; Morgon, Nelson H
  • Atividade inibitória de pesticidas piretroides sobre a glutationa S-transferase Artigo

    Ribeiro, Eliane B; Badea, Mihaela; Ribeiro, Danilo B; Costa, Andressa R. C; Santos, Djanira R. dos; Marques, Paulo R. B. O; Nunes, Gilvanda S

    Resumo em Português:

    Glutathione S-transferase (GST) is one of the enzymes used to evaluate the effects caused by environmental contaminants. The aim of this work was to study the effects of four pyrethroid compounds (allethrin, cypermethrin, deltamethrin and fenpropathrin) on the catalytic activity of GST and to estimate the potential for environmental contamination in silico of these insecticides. Spectrophotometric analyses showed that the activity of the GST enzyme was inhibited by the four pesticides, with the values for the inhibition constant (Ki) varying from 0.12 to 20 µmol L-1, with the following order of inhibition from the highest to the lowest Ki value: deltamethrin > cypermethrin > allethrin > fenpropathrin. They presented a competitive and non-competitive inhibition mechanism depending on the compound. The IC50 values (concentration that inhibits 50% of the enzyme activity) showed the insecticide deltamethrin with greater inhibitory capacity, since it reduced the activity of the GST enzyme by half, even though it was in a lower concentration in relation to the other analyzed compounds. The in silico evaluation indicated the possibility of most of the insecticides contaminating the surface waters (rivers and lakes) adhered to the suspended sediment, but did not show any potential for contamination of groundwater through leaching.
  • Preparation of fluorescent polystyrene microspheres by improving swelling performance based on molecular weight and surface carboxyl group content Artigo

    Sun, Fei; Feng, Chao; Wang, Yang; Yang, Xue; Zhao, Hong

    Resumo em Inglês:

    The fluorescent microspheres are prepared by the swelling-evaporation method. The optimal swelling conditions are obtained by researching related factors, such as types and dosages of swelling agent, dosages of fluorescent substance, swelling time and swelling temperature. Considering that the structure of microspheres can influence the swelling properties, the paper mainly focuses on the effect of molecular weight and surface carboxyl group content of polystyrene microspheres on swelling properties. When the molecular weight of microspheres is 75276 g mol-1, the density of carboxyl group on their surface is 6.94×10-4 mol g-1, and the doping amount of europium complex reaches the maximum of 24.9 mg g-1 with the strongest fluorescence intensity. Meanwhile, the as-prepared fluorescent microspheres have high monodispersity, uniform particles size and high thermal stability (the decomposition temperature is 385oC), which sets up the good foundation for biomolecule detection. So, this work provides a significant experience for the preparation of fluorescent microspheres.
  • Optimization of eugenol-loaded microcapsules obtained by spray drying using a simplex-centroid mixture design Artigo

    Bittencourt, Paulo Rodrigo Stival; Veiga, Ruth dos Santos da; Silva-Buzanello, Rosana Aparecida da; Scremin, Fernando Reinoldo; Becker-Algeri, Tania Aparecida; Corso, Marinês Paula; Flores, Éder Lisandro de Moraes; Canan, Cristiane

    Resumo em Inglês:

    Eugenol antioxidant and antibacterial properties have suggested its use as a natural preservative for food matrices. Eugenol application is compromised due to its high volatility and sensibility to external agents, such as light, heat, oxygen, and moisture. Thus, microencapsulation is viable to increase the eugenol stability. Results have showed that carrageenan combined with rice protein and bovine albumin allow high-quality eugenol microcapsules. These materials show excellent properties, favoring the microcapsules use in food matrices. This study aimed to optimize microcapsules formulation by spray drying, using a simplex-centroid mixture design. Blends of low-lactose whey protein (WP) and/or rice bran protein (RBP) and/or bovine serum albumin (BSA) with carrageenan were used as wall materials. Blends influenced the eugenol retention, microencapsulation efficiency, and size. Pure WP was not efficient for eugenol encapsulation. The highest eugenol retention values, 89.7% and 86.5% were obtained by combining carrageenan with RBP or BSA. RBP and BSA binary interaction with carrageenan showed the highest encapsulation value (80.5%). Scanning electron microscopy, infrared spectroscopy, and thermogravimetry confirmed eugenol inside the microcapsules.
  • Molecular dereplication of volatile oils from Saururus cernuus L. and evaluation of anti-Trypanosoma cruzi activity Artigo

    Brito, Juliana R; Costa-Silva, Thais A; Londero, Vinicius S; Baldim, João L; Tempone, Andre G; Ferreira, Edgard A; Lago, João Henrique G

    Resumo em Inglês:

    The present study reports the molecular dereplication and the evaluation of anti-Trypanosoma cruzi activity of volatile oils from inflorescences, leaves, branches, and roots of Saururus cernuus L. (Saururaceae). Chemically, the oils showed the predominance of sesquiterpenes in inflorescences (64.04%) and branches (63.82%), with β-sesquiphellandrene (25.50%) and (E)-caryophyllene (22.40%) corresponding to the main constituents of each oil. Furthermore, it was possible to detect safrole as the most predominant compound in the leaves oil (49.09%). On the other hand, the oil from roots was mainly composed by monoterpenes (84.60%), with limonene in higher concentration (38.41%), followed by α-pinene (20.19%), and camphene (14.71%). The oils from inflorescences and branches displayed higher antitrypanosomal potency with EC50 values of 7.1 and 8.8 μg mL-1, respectively, followed by the oils from the roots and inflorescences, with EC50 values of 17.3 and 30.4 μg mL-1, respectively. Additionally, branches and inflorescences oils displayed no toxicity in mammalian NCTC cells (CC50 > 200 μg mL-1). Using two PLS-DA methods, it was possible to suggest that the anti-T. cruzi activity of the tested oils could be associated with the presence of β-sesquiphellandrene, safrole, β-elemene, and α-zingiberene whereas threo-austrobailignan-5, β-sesquiphellandrene, α-humulene, germacrene D, and bicyclogermacrene play a role in the cytotoxicity against NCTC cells.
  • Ficocianina como indicador de cianobactérias em reservatórios Artigo

    Silva, Thiago T. da; Albuquerque, Rufina A. M; Becker, Helena

    Resumo em Português:

    Phycocyanin is a pigment present in cyanobacteria whose optical characteristics favor its application in clinical, dietary, and environmental aspects. There are reports of studies of these pigments in lakes and reservoirs, which present different analysis methodologies. Based on this information, this work aims to evaluate correlations between phycocyanin and the number of cyanobacteria to optime the methodologies mentioned above. The samples were collected from four reservoirs in the semiarid region of Ceará, and the applied methodology was based on the work of Hórvath (2013). The spectrophotometry and the fluorimetry analyzes were performed in this analysis. The analytical curves for the phycocyanin showed high linearity, and the fluorimetric technique, which was used due to its greater analytical sensitivity. The absorbance coefficient (2.57 mL mg-1 cm-1) was obtained by spectrophotometry, which was lower than that reported in the literature. The correlations found were higher and significant for phycocyanin (r > 0.70) for the reservoirs, while the correlations with chlorophyll were much lower, hence is contrary to what was observed in the literature. It is concluded that the phycocyanin pigment should be used as an indicator in the estimation of cyanobacteria in reservoirs, replacing the use of chlorophyll for the same function.
  • Cinética de pirólise para o sorgo lignocelulósico: análise de dados termogravimétricos para aplicação do modelo de Friedman Artigo

    Silva, Matheus H. B. P. da; Oliveira, Tiago J. P. de; Ataíde, Carlos H; Cerqueira, Daniel A; Sousa, Nádia G; Cardoso, Cássia R

    Resumo em Português:

    Renewable resources are alternatives to fossil fuels and pyrolysis is identified as a process for the generation of biofuel products. The lignocellulosic sorghum is a cereal produced in brazil and it presents several applications, such as the production of second-generation ethanol. The present work aimed to study the slow pyrolysis of lignocellulosic sorghum, the biomass was characterized by means of proximate, ultimate, composition and carbohydrate analyzes. Thermogravimetric analyzes were performed with heating rates between 5 and 25 K min-1 and with N2 atmosphere. The Friedman model allows obtaining the kinetic parameters of biomass decomposition and is widely used due to its simplicity and precision; however, since it is sensitive to experimental noise, an algorithm was developed for the calculation of kinetic parameters for the slow pyrolysis of this biomass, enabling an accurate analysis of the experimental data. The activation energy found by the proposed methodology was 122.65 ± 19.24 kJ mol-1, with determination coefficients above 0.97. The comparison between experimental and theoretical data presented deviation values of 0.934%, 3.408% and 1.101% for heating rates of 5, 10 and 15 K min-1, respectively, showing the accuracy for the determined kinetic parameters.
  • Métodos analíticos para determinar lactonas macrocíclicas en diferentes tipos de matrices. una revisión Revisão

    Vázquez-Quintal, Patricia Esmeralda; Rodríguez-Vivas, Roger Iván; Muñoz-Rodríguez, David

    Resumo em Espanhol:

    ANALYTICAL METHODS FOR DETERMINATION OF MACROCYCLIC LACTONES IN DIFFERENT TYPES OF MATRICES. A REVIEW. The macrocyclic lactones (ML) are drugs widely used to combat endo- and ectoparasites in livestock, pets, crops, etc. Since marketing of ivermectin, the number of available ML increased considerably and, consequently, a wide variety of analytical methodologies for determination of MLs in multiple types of matrices have been published. Most of these methodologies have already been reviewed before so this paper is about those most recent and/or those have not been previously considered. In this review the focus is on biological, alimentary, and environmental matrices emphasizing on the most important techniques employed on sample preparation. Also, the liquid chromatography with of fluorescence and mass spectrometry detectors is discussed as the most used instrumental techniques for identification of MLs. Finally, a brief review is made on the importance of method validation and some strategies for its implementation.
  • Uma breve revisão sobre a catálise por átomos isolados: conceitos e aplicações Revisão

    Ferreira, Luanne E. M; Ribeiro, Ruan S. A; Madriaga, Vinicius G. C; Vasconcelos, Sancler C; Shimabukuro, Eric T. T; Rossa, Vinicius; Vieira, Sara S; Passos, Fabio B; Lima, Thiago M

    Resumo em Português:

    A BRIEF OVERVIEW ON SINGLE-ATOM CATALYSIS: CONCEPTS AND APPLICATIONS. Catalytic processes became extremely important for the development of our society, especially after the second industrial revolution. Thus, the research for more efficient catalysts is an obstacle to overcome to achieve cheaper processes, higher yields, and selectivity of desired products. In this context, single-atom catalysis emerges as a promising alternative to unite the advantages of traditional homogeneous and heterogeneous catalysis. Catalysis by single-atoms is a bridge that unites in a single catalyst the ease of recovery and reuse (from heterogeneous catalysis) with the high exposure and uniformity of sites (from homogeneous catalysis). Thus, single-atom catalysts (SACs) and single-atom alloys (SAAs) have already found several applications in the literature, such as in hydrogenation, oxidation, conversion of biomass derivatives, electrocatalysis, and photocatalysis. However, it is essential to emphasize that it is still a field that is expanding and relatively new, with several opportunities and many barriers to surpass. In this review, concepts of homogeneous, enzymatic, and heterogeneous catalysis will be addressed, as well as fundamental aspects of single-atom catalysis, preparation methods, characterization, and current challenges.
  • Edulcorantes de alta intensidade: tendências de uso em alimentos e avanços em técnicas analíticas Revisão

    Nicoluci, Ícaro G; Takehara, Carolina T; Bragotto, Adriana P. A

    Resumo em Português:

    HIGH-INTENSITY SWEETENERS: TRENDS OF USE IN FOODS AND ADVANCES IN ANALYTICAL TECHNIQUES. The high consumption of sugar by the population and its correlation with the increase in the rates of obesity and chronic non-communicable diseases have promoted discussions of strategies to reduce the intake of this ingredient. In addition to consumer campaigns and governmental public policies, the use of high-intensity sweeteners to replace sugar in foods could be a feasible alternative for reducing sugar intake. However, it is important that high-intensity sweeteners be used considering the maximum permitted levels and approved food categories according to the current legislation. In this context, the development and application of analytical methods to determine high-intensity sweeteners in foods is a current and relevant issue. This manuscript aims to review the general aspects and available analytical techniques for the determination of these additives in food matrices.
  • Avaliação analítica de analisador de combustível comercial no controle de qualidade de etanol e gasolina comum Nota Técnica

    Sena, Sthefany dos S; Ferreira, Ernesto C

    Resumo em Português:

    ANALYTICAL EVALUATION OF COMMERCIAL FUEL ANALYZER IN GASOLINE AND ETHANOL FUEL QUALITY CONTROL. Brazilian news media is full of examples about fuels out of the compliances and needs to control fuel quality. This work proposed an analytical validation of a commercial near infrared photometer (Xerloq, Tech Chrom Analytical Instruments, Brazil) able to identify percentage of ethanol in fuels comparing with NBR standards. Four procedures were selected: analysis of ethanol percentage in gasoline type C samples comparing with standard method ABNT 13992; analysis of ethanol percentage in fuel ethanol samples comparing with standard method ABNT 5992; linearity correlation and selectivity of standard solution analysis. Comparisons between the photometer and standards measurements were to determine the accuracy and precision of the device which presented a little variation from the norm (ER < 1.3%, sR < 0.4%). With regard to the test for linearity, Ethanol:water mixtures was analyzed with R-squared larger than 0.999 with RMSEV less than 1%. On selectivity tests, Gasoline:Ethanol:water and Methanol:Ethanol:water mixtures were measured with bias error not exceeding 5% for regulated samples. In conclusion, this fuel analyzer can be used to analyze ethanol content in Brazilian fuels with similar results comparing with classical standard volumetric and glass densimeter analysis and may indicate adulteration gasoline and ethanol samples by anomalous data.
  • Construção, otimização e ancoragem molecular de substâncias bioativas em biomacromoléculas: um tutorial prático Nota Técnica

    Batista, Victor S; Farias, Renan L; Simões, Leonardo P. M; Nascimento-Júnior, Nailton M

    Resumo em Português:

    CONSTRUCTION, OPTIMIZATION AND MOLECULAR DOCKING OF BIOACTIVE SUBSTANCES IN BIOMACROMOLECULES: A PRACTICAL TUTORIAL. In the last two decades, increasing advances in molecular biology and instrumental analysis for solving macromolecular structures have amplified the applicability of cheminformatics in drug discovery. In particular, molecular docking, an in silico structural-based method, has prospered as an efficient tool for understanding molecular interactions that drives formation of stable receptor-ligand systems. Brazil affords many research groups working hard on this subject; however, there is a lack of material in the Portuguese language, teaching how to apply molecular docking methodologies. Herein, we define and discuss a simple and low-cost workflow for molecular docking evaluation, comprising software installation (supplemental material) and how to use them for construction of small-molecules, perform docking calculations, analysis of the results and the preparation of quality figures. Given that, we have used free software and web-servers, as well as in silico tools supported by national funding agencies.
  • Cerveja egípcia? Educação para as relações étnico-raciais (ERER) na formação docente em Química Educação

    Silva, Eliete Lucia; Camargo, Marysson Jonas Rodrigues; Benite, Anna Maria Canavarro

    Resumo em Português:

    EGYPTIAN BEER? EDUCATION FOR ETHNIC-RACIAL RELATIONS (ERER) IN TEACHER FORMATION IN CHEMISTRY. This work was carried out in a Higher Education Institution (IES), in the State of Goiás, in the Chemistry Degree course, aiming at the implementation of Law 10639/03. The context discussed herein is the chemical knowledge of African and diasporic matrices from Ancient Egypt in the development and production of beer. In order to subsidize teachers in initial formation with strategies in the classroom for an anti-racist education, taking into account the contribution of African people in the constitution of the country. It is an action research and its development happened through a Pedagogical Intervention (IP) with the theme: Ancient Egypt, Beer and Chemistry. The results were collected through audio recording and analyzed using the Conversation Analysis technique. Our results have shown that it is possible to talk about African history and culture, in a chemistry class in the initial chemistry teacher training course, making an epistemic shift in the curriculum, taking previously silenced knowledge to school, such as the history and culture of African peoples.
  • Microlearning as a tool for scientific dissemination: thermal analysis of the Portuguese good luck rooster Educação

    Magri, Raquel; Gaglieri, Caroline; Alarcon, Rafael Turra; Souza, Aguinaldo Robinson de; Bannach, Gilbert

    Resumo em Inglês:

    This work aims to produce and disseminate videos that follow the microlearning methodology, to explain the physicochemical properties of cobalt (II) chloride hexahydrate through thermal analysis, and to determine the reliability of the Portuguese good luck rooster. Temporal and social accelerations due to the growth of the technological world are changing the old teaching-learning methodologies; thus, new methods should be explored. In the microlearning methodology, short segments and specific content can be broadcast to anyone at any time. In addition, relating new information to individual’s experiences can favor the teaching-learning process. The good luck rooster is an ornament of Portuguese origin, which can forecast the weather in a limited way, and is composed of cobalt (II) chloride hexahydrate. This compound was characterized by TG-DTA (Simultaneous Thermogravimetry-Differential Thermal Analysis) and DSC (Differential Scanning Calorimetry), verifying that the salt loses its hydration water when exposed to high temperatures, changing its color from pink color to blue.
  • Anais dos ENEQ: o que nos dizem sobre a área de educação em química no Brasil? Assuntos Gerais

    Alexandrino, Daniela Marques; Bretones, Paulo Sergio; Queiroz, Salete Linhares

    Resumo em Português:

    ENEQ ANNALS: WHAT DO THEY TELL US ABOUT CHEMISTRY EDUCATION AREA IN BRAZIL? Academic production on Chemistry Education in Brazil is abundant. The network of participants that contribute to it is vast, spread across all geographic regions. This network is responsible for carrying out actions that have led to consolidating the area of Chemistry Education. This article analyzes all the annals now available from the Encontro Nacional de Ensino de Química (ENEQ) and establishes relationships between events that took place at the conferences and the previously mentioned consolidation (analysis period: 1982 to 2018). In addition, the authorship of the works presented at ENEQ (analysis period: 1982 to 2010) was investigated, enabling us to identify professionals who offered relevant contributions to help construct the current scenario in the area.
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