Doutorado em Química (IQ)

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    Desenvolvimento de metodologias miniaturizadas de preparo de amostras para a avaliação de pesticidas multiclasses em amostras ambientais
    (Universidade Federal de Goiás, 2023-09-05) Martins, Rafael Oliveira; Silva, Bruno José Gonçalves da;; Chaves, Andréa Rodrigues;; Chaves, Andréa Rodrigues; Nascentes, Clésia Cristina; Coltro, Wendell Karlos Tomazelli; Hantao, Leandro Wang; Sgobbi, Lívia Flório
    The presence of pesticides in the environment is primarily due to the excessive use of these chemical compounds in the global agricultural scenario. In recent decades, the search for new approaches to the analysis and monitoring of these compounds in such matrices has focused on the introduction of sample preparation methodologies as analytical strategies responsible for assessing such complex matrices. Furthermore, the evolution of these sample preparation methodologies over the decades has brought with it the introduction of miniaturized systems capable of overcoming classical challenges faced by conventional sample preparation method-ologies. Thus, this study presents the evaluation of three miniaturized approaches for pesticide extraction in environmental samples. Chapter II presents the development and application of the Hollow Fiber Liquid-Phase Microextraction (HF-LPME) technique for the assessment of 13 multi-class pesticides in soil samples. The methodology reported in the first chapter resulted in R² values >0.98 for all pesticides and detection and quantification limits (LOD and LOQ, re-spectively) in the range of ng L-1 and recovery values between 75.2%-118.8%. The evaluation of the methodology proposed by the AGREEprep software indicated that approximately 70% of the method adhered to the principles of green chemistry adopted by the software. Furthermore, a comparison with classical methods of pesticide extraction in soil identified the HF-LPME method as an efficient approach for monitoring pesticides in soil. Chapter III describes the application of the Electromembrane Extraction (EME) technique for the evaluation of the same set of analytes in soil samples. In this second approach, a special focus was placed on com-paring the proposed method with the one applied in Chapter II, regarding analytical frequency, green aspects, and analytical performance of both methods. Differences were observed in an-alytical aspects, where the EME technique showed higher LOD (76.1 -171.4 μg kg-1) and LOQ (270.7 -516.1 μg kg-1) values than the HF-LPME technique (66.1 -198.1 μg kg-1) and (92.7 -331.2 μg kg-1), respectively. Despite this, values closer to 100% were obtained with the EME technique. A higher analytical frequency was achieved with the EME technique (4 extractions/h) compared to HF-LPME (2 extractions/h). Regarding green chemistry aspects, due to the use of external energy, the methodology proposed by EME showed significant energy consumption. Finally, Chapter IV presented a detailed study of the influence of parameters involved in the on-chip electromembrane extraction technique of the pesticides Carbofuran and Carbendazim in river water samples. This chapter focused on two main aspects: (I)the optimization of the device to reduce leakage during extraction, as it is a disadvantage of the conventional system, and (II)evaluating the differences in the extraction of ionizable and neutral compounds by the on-chip electromembrane extraction system. The optimization of the device introduced the OSTE sealing material as an approach to prevent leaks, allowing for the use of flow rates of 300 μl/min-1 without observing leaks. The evaluation of the parameters involved in the technique showed the dependence of the physicochemical characteristics of the pesticides on the pro-posed system, revealing the extraction of the pesticides in their charged and neutral forms. The analytical evaluation of the method showed LOD and LOQ values ranging from 158.4 to 256.2 μg L-1and 528.1 to 854.1 μg L-1, respectively, and recovery values ranging from 26.3% to 53.8%, indicating an influence of the matrix that was confirmed by the matrix effect study. The study of the pesticides Carbaryl and Carbendazim proved to be an important approach to further expand the field of applications of the on-chip electromembrane extraction technique. The methods described here have proven to be effective analytical strategies for assessing pesticides in en-vironmental samples. The development of the methodologies presented here further expands the possibilities for monitoring pesticides in such complex samples as environmental ones. The application of the proposed methodologies offers a possible strategy for evaluating the effects of these compounds on the environment and proposing ways to identify contaminants in differ-ent environmental compartments.
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    Síntese e caracterização de catalisadores nanoestruturados contendo PtSnCu para a oxidação eletroquímica de etanol
    (Universidade Federal de Goiás, 2019-11-28) Magalhães, Monah Marques; Colmati Júnior, Flávio;; Colmati Júnior, Flávio; Ribeiro, Josimar; Souza, Elki Cristina de; Sgobbi, Lívia Flório; Cabral, Murilo Feitosa
    Renewable energies are increasingly desirable. One of the proposed alternatives is proton-exchange membrane fuel cells (PEMFC). The use of ethanol as fuel in these cells is advantageous because it has a low contribution to the greenhouse effect when the CO2 cycle is completed. However, complete oxidation of the ethanol requires the breaking of the CC bond, to oxidize the intermediates that are formed during the reaction, which are stable and if not oxidized promote a decrease in the efficiency, due to the poisoning of Pt. The study is presented with catalysts of PtxSnyCuz supported on high surface area colloidal carbon. The electrocatalysts were produced with the alcohol reduction method. The synthesis used with modification to obtain the materials allowed the formation of nanoparticles with high catalytic activity, in the range of 2 to 3 nm. The physical characterization techniques used, such as XRD, MET and XPS, allowed to verify that the particles are crystalline, with majority crystal of the CFC structure of Pt, and that Sn and Cu atoms were inserted in this crystal, causing modifications in the peaks to the crystalline planes of the Pt network. Microscopies showed the morphology of the nanoparticles and helped to understand the relation of the high catalytic activity with the good dispersion of particles and their high surface area coming from their size. The analysis by XPS allowed to prove the elements present in the samples, besides determining the composition of atoms in the surface in which the catalysis occurs. The electrochemical characterization by VC showed the high activity of the ternaries with low potential values for the beginning of the ethanol oxidation compared to the Pt/C, PtSn/C and PtCu/C catalysts. The chromaamperometric technique evaluated the stability of the catalysts and verified that in the studied time the materials have constant and stable behavior. Through the EIS it was possible to understand the electrical resistance of the catalytic surface and to verify that such property for the ROE decreases as the potential increases, the studied compositions showed that the composition of the material influences in the reduction of the electrical resistance when oxidizing the molecule of ethanol and that can two or more reaction mechanisms occur during catalysis.
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    Estudo químico, quimiotaxonômico e avaliação antiofídica de espécies dos gêneros Copaifera e Marsypianthes
    (Universidade Federal de Goiás, 2022-12-21) Teixeira Júnior, Eurides Francisco; Kato, Lucilia;; Kato, Lucilia; Torres, Ana Maria; Silva, Carmelita Gomes da; Rosa, Jeane; Sena, Marcelo Martins de
    Snakebites have a major impact on public health, especially in isolated communities without access to prompt medical attention. There are about 100,000 deaths per year caused by snakebites and three times as many sequelae. The antivenom is the conventional treatment, but it has no action at the site of the bite in the human body and is not always within the reach of victims in isolated locations. The use of plants as treatment in case of snakebites is a reality, because it is an accessible way, with lowcost resource that attenuates the local effects of the bite too. The species Marsypianthes chamaedrys, known in the northern region as Boia-cáa or Paracari, is widely used in these cases. In Brazil, besides M. chamaedrys, also occur M. foliolosa, M. montana, M. burchelli, M. hassleri and M. tubulosa. Except for the first, the other species are still poorly studied. This work allowed the annotation of metabolites and evaluation of the anticoagulant and anti-hemolytic action for Marsypianthes species not studied so far. The anti-hemolytic action of the M. montana extract stands out. In ethnobotanical studies, the oil extracted from the trunk of copaibas is reported in cases of ophidic accidents. In this study, we confirmed the anticoagulant and anti-hemolytic action of the leaf extract of different taxa of Copaifera against Bothrops alternatus venom. The species Copaifera sp. and C. marginata totally inhibited the coagulant action of the venom, and the latter showed more than 95% inhibition of hemolytic activity. The Copaifera genus is composed of over 70 species, of which 16 occur only in Brazil. There are many gaps in the correct identification of species and varieties of this genus. Using direct infusion mass spectrometry data associated with chemometric methods such as PLS-DA, it was possible to identify the main ions responsible for the distinction of four taxa of Copaifera, including varieties of the same species. Thus, this work fulfills its objective of providing chemical and biological information about species of the genera Copaifera and Marsypianthes. Taking advantage of powerful tools such as the HPLC-MS/MS and the GNPS platform, it was possible to note several metabolites, among which, many phenolic compounds, which may be associated with the investigated antiphidic actions.
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    Gaseificação catalítica de efluente da indústria de biodiesel para a produção de hidrogênio
    (Universidade Federal de Goiás, 2023-04-28) Mourão, Lucas Clementino; Alonso, Christian Gonçalves;; Alonso, Christian Gonçalves; Corazza, Marcos Lúcio; Chagas, Rafael Pavão das; Colmati Júnior, Flávio; Alves, Helton José
    The increasing global pollution, combined with a growing demand for energy, is driving the search for environmentally-friendly alternatives in energy production. Hydrogen, which has emerged as an important energy vector, is primarily produced from non-renewable sources such as petroleum. The development of innovative technologies has facilitated the utilization of renewable sources for hydrogen production, such as Supercritical Water Gasification (ScWG) of biomass. Among the potential feedstocks for hydrogen production, glycerol, a byproduct of the biodiesel industry, stands out as a promising candidate for ScWG. Due to the increasing production of biodiesel, a large supply of glycerol is being produced without a corresponding increase in demand. As a result, the biodiesel production chain has garnered increased interest from several research initiatives aimed at valorizing waste materials into higher value-added products. Combined with heterogeneous catalysis, the ScWG process can increase selectivity towards products of interest and achieve high conversion efficiency of organic matter, even with short residence times. In this work, the catalytic gasification of glycerol and real wastewater from a biodiesel industry were evaluated. Ni based catalyst were synthetized by simple and fast wet impregnation method of metallic nitrates supported on a honeycomb cordierite (CRD) structure. The catalysts were characterized by SEM-EDS, XRD, N2 adsorption/desorption, XRF, WDS and TGA. The performance of the Ni-based catalyst was evaluated in the ScWG of glycerol and compared to two commercial Automotive Catalysts (ACs). The ScWG of glycerol was carried out under different conditions in order to establish optimal operating parameters. The tests were conducted at reactor temperatures ranging from 400ºC to 700ºC, a system pressure of 25 MPa, and glycerol mass concentrations ranging from 10% to 34%. For optimal conditions (600 ºC and glycerol 10wt%), the results indicated that Ni/CRD catalyst showed the highest H2 yield (1,40 mol/mol C) and carbon conversion (95%). Although they have shown efficiency in the gasification of glycerol, the ACs showed higher tendencies for activity loss in carbon conversion compared to Ni based catalys over time (300 min). Preliminary tests using real industrial effluent (BIOD) were conducted, evaluating parameters of temperature (400 - 600°C), feed flow rate (10 - 20 mL/min), and effluent concentration based on total organic carbon (TOC) (50 - 100%). The results showed that temperature had the greatest influence on gasification, with a carbon conversion of 77% and an H2 yield of 2.85 mol/mol C at 600°C (10 mL/min; 50% TOC). Catalytic test conducted under the best condition (600 ºC; 10 mL/min; 100% TOC) showed higher carbon conversion, while non-catalytic test obtained higher H2 selectivity (76%). The results showed that structured catalyst has great potential to enhance the production of H2-rich gas specially from glycerol GASc. The use of biodiesel residue as a raw material for the ScWG process is promising since it allows the treatment of the residue and the production of H2-rich gas simultaneously.
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    Desenvolvimento de novos sais do fármaco adifenina com estabilidade física e química aprimoradas, avaliação da biodisponibilidade e estudos de estabilidade físico-química em formulação
    (Universidade Federal de Goiás, 2022-06-23) Ribeiro, Thiago de Freitas; Oliveira, Cecília Maria Alves de;; Oliveira, Cecília Maria Alves de; Doriguetto, Antônio Carlos; Carvalho, Jesiel Freitas; Gomes, Danielle Cangussu de Castro; Kato, Lucília
    Here we have solved the adiphenine solid-state hygroscopicity problem through the preparation of stable, non-hygroscopic multi component crystal forms thereof. Two new salts of adiphenine were designed by recognition of intermolecular interactions patterns in the Cambridge Structural Database (CSD) and pKa rules. Some conformants, Generically Recognized as Safe (GRAS), namely malic acid, fumaric acid, lactic acid, citric acid and oxalic acid, were selected for the synthesis of monobasic salts with an adiphenine base, and they had a favorable result in this two synthesis step, namely, are the citrate and oxalate salts. Crystal structure elucidation reveals that adiphenine adopts different conformations in our salts and in the literature hydrochloride one, which is related to different intermolecular arrays. The adiphenine hydrochloride exhibits a classical high hygroscopicity behavior, which retains water fast from 50% of relative humidity (RH), increasing up to 22% of its initial mass in 90% of RH and a net mass gain of 5% at the end of the desorption cycle (RH = 0%). In the dynamic vapor sorption(DVS) analysis, it was verified that adiphenine citrate and adiphenine oxalate starts to incorporate water slowly from 50% and 70% of relative humidity (RH), increasing up to 3.2% and 2.6% of their initial masses in 90% of RH, respectively. At the end of the desorption cycle (RH = 0%), the samples retained only 0.12% and 0.08% of water relative to their initial masses. Notably, both carboxylic acid salts had similar solubility as a function of medium pH, while the hydrochloride one was more soluble than them by factors ranging from 6.7 (relative to citrate in pH 1.2) to 28.2 (relative to oxalate in pH 4.5). Nevertheless, them pharmacokinetic parameters of adiphenine after oral administration of the capsules containing the salt forms did not reflect these solubility differences, since all adiphenine salt forms can be considered highly soluble drugs according to Biopharmaceutics Classification System (dose/solubility ratio <250mL). It was observed that the rats treated with capsules containing adiphenine hydrochoridrate had an increase in AUC0-∞ (1537 vs 914 vs 991 min μg mL-1 ) compared with rats treated with adiphenine citrate and oxalate capsules, respectively, even though the same Tmáx (48 min) was observed. The dosage tuning can bring the bioavailability of our salts into that of the hydrochloride salt, with the advantage of non-hygroscopicity and higher chemical stability. The study stability was also carried out in a known formulation and the result obtained confirmed that the new adiphenine salts are more stable when exposed to stress conditions. The evaluation of the stability of the adiphenine salts in the formulation was carried out in such a way that it was possible to assess whether the adiphenine salts would withstand certain stress conditions in the salt form and after being incorporated into the formulation. Under photolytic and humid thermal stress conditions, the stability of the new adiphenine salts is remarkable, since the content obtained did not show a sharp drop, in addition, the main adiphenine degrading agent did not show a high % when compared to commercially available salt. We highlight, in isolated active pharmaceutical ingredients, the degradation between the commercially available salt and the new salts is similar with degradation lower than 1.6% when exposed to wet thermal and photolytic conditions. However, when active ingredients are incorporated into a formulation, the difference in the degradation process is clear. Since the commercially available salt degraded 9.5% in the thermal condition and 2.5% in the photolytic condition in variation the new salts of adiphenine citrate and oxalate degraded 1% and 1.9% in the thermal condition and 0.7% and 1.0% in the photolytic condition, respectively
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    Estudo do cloridrato de fenilefrina em associação com outros insumos farmacêuticos ativos: compatibilidades físico-químicas, identificação e qualificação de produtos de degradação
    (Universidade Federal de Goiás, 2022-09-02) Silva, Alisson Moraes e; Oliveira, Cecília Maria Alves de;; Oliveira, Cecília Maria Alves de; Martins, Felipe Terra; Leles, Maria Inês Gonçalves; Valadares, Marize Campos; Guimarães, Vinícius Ferraz
    Phenylephrine hydrochloride is a medication widely used in medicine to increase blood pressure during surgical procedures and to promote objective and subjective relief of nasal congestion in patients with the common cold. For this reason, it is largely used in fixed-dose combination medicines, associated with active pharmaceuticals ingredients (APIs) such as acetaminophen, caffeine, dexchlorpheniramine maleate, pheniramine maleate, and acetylsalicylic acid. Given the well-known chemical instability of phenylephrine hydrochloride and in order to increase the knowledge about the interactions of this API with other medications, in this thesis the results of Differential Scanning Calorimetry (DSC) and Thermogravimetry (TGA) curves of isolated APIs: phenylephrine hydrochloride, paracetamol, caffeine, acetylsalicylic acid, dexchlorpheniramine and pheniramine maleates and the drug-drug compatibility studies under stress conditions, in solid phase, for binary mixtures containing phenylephrine hydrochloride in association with other APIs were evaluated and discussed. Furthermore, in order to obtain data on the degradation products formed from the interactions of the associations tested, the use of techniques such as high-performance liquid chromatography coupled with ultraviolet-visible detector (HPLC/UV-VIS) and with high resolution mass spectrometer (HPLC/HRMS) were employed to quantify and elucidate the structures of impurities formed in the associations tested and in products available in the local market. The genotoxic potential of these compounds was also evaluated in silico using the Genotox-iS® 3.0 toxicological prediction software. The data obtained attested that phenylephrine hydrochloride is a hygroscopic API, physically incompatible with acetylsalicylic acid and with APIs that have maleate as a counterion. The investigation of the degraded samples allowed elucidating the structures of the degradation products formed of which only compounds named in this work as I and IV are reported in the literature, however, without mention for their toxicity. The detected degradation products were qualified in silico according to the prerogatives of the The International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use (ICH) M7 guide, and categorized as class 5 (non-mutagenic): compounds I, II and III and class 3 (structural alert, not related to the structure of the drug substance; no mutagenicity data): compound IV. Three of the commercially available medicines tested exhibited the presence of high concentrations of Compound I.
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    Tecnologia supercrítica aplicada ao tratamento de águas contaminadas por fármacos
    (Universidade Federal de Goiás, 2022-04-29) Dias, Isabela Milhomem; Alonso, Christian Gonçalves;; Alonso, Christian Gonçalves; Silva, Fábio Moreira da; Freitas, Fernanda Ferreira; Sgobbi, Lívia Flório; Coltro, Wendell Karlos Tomazelli
    The growth of the world population has led to the increased disposal of pharmaceutical products in the environment. Also, a wide variety of drugs used for the prevention and treatment of diseases have a low metabolic rate in humans and are often released into the environment in their unaltered form. These contaminants may offer potential risks to human health and the ecosystem. As a consequence, water is one of the most affected parts, because it is involved in various human activities. Currently, there are several processes used in water treatment, which use physical, chemical, and biological methods to remove pollutants from wastewater. However, methods of wastewater treatment have not demonstrated efficiency for the complete degradation of these compounds, or they are often impractical to treat a large volume of residues. With regard to the need to effectively treat these pollutants, this study presents the investigation of the supercritical water oxidation (SCWO) process applied in the treatment of aqueous residues contaminated with pharmaceuticals using a continuous flow reactor. For this purpose, it was investigated the degradation of amoxicillin in industrial pharmaceutical effluent, antibiotics, anxiolytics/antidepressants, and antihypertensive/cardiovascular drugs in an aqueous solution. Reaction tests were separated by therapeutic classes. In that way, a total of 20 drugs were evaluated. For all four scenarios related to each pharmaceutical class, the conditions of temperature, flow rate, and H2O2 concentration were optimized to maximize the total organic carbono removal rate (%RCOT). In the degradation of industrial effluent contaminated with amoxicillin, both temperature and flow parameters had the greatest effect on the %RCOT of the liquid phase, whose maximum value reached was 60.1%. In the gaseous product, the formation of H2, CO2, and CH4 stood out with a total volumetric flow of 6.45 mL/min. In the degradation of 6 antibiotics in an aqueous solution, the temperature was the most significant effect to achieve a %RCOT of 64.1%. The gaseous product, mostly H2 and CO2, had a total volumetric flow rate of 18 mL/min, a value almost 3 times greater than the feed flow rate. During the degradation of 5 anxiolytic/antidepressant contaminants, both parameters of temperature and H2O2 concentration had the greatest impact on %RCOT (85.9%). The total gas flow rate was 11 mL/min and, once again, among the 6 gases determined in the gaseous product, H2 and CO2 were more relevant. In the treatment of cardiovascular/antihypertensive drugs, the maximum %RCOT achieved was 92.1%, and both temperature and H2O2 concentration parameters had the greatest influence on this response. CO2 (98%) was the major constituent of the gas composition that had a total volumetric flow of 26.3 mL/min, which corresponds to twice the feed flow rate used. Briefly, for most of the four scenarios studied, the optimized conditions of temperature, flow rate, and H2O2 concentration were approximately 692°C, 6.6 mL/min, and 292% (m/m), respectively. With an exception in the cardiovascular/antihypertensive degradation condition that occurred at a lower temperature (601°C), intermediate flow rate (13.3 mL/min), and low H2O2 concentration (65%; m/m). Furthermore, for all cases evaluated, most of the limits recommended by national and international legislation regulating water quality were met. In the toxicity essays, exposure to the microcrustaceans Artemia salina revealed toxicity for some treated samples. The lethal concentration, in %(v/v), to kill 50% of the population (LC50) were approximately 12%, 555%, 32%, and 4% for industrial effluent with amoxicillin, and for all aqueous solution with antibiotics drugs, anxiolytic/antidepressant drugs, and cardiovascular/antihypertensive drugs, respectively. Given that, the SCWO technology applied to the treatment of wastewater contaminated with drugs revealed simultaneously, high oxidative power of organic matter and production of valuable energy gases, such as H2, methane, and synthesis gas. The toxicity of some molecules produced is a challenging issue to be addressed. However, due to the high oxidative power, volume and speed of waste processing, the positive contributions of SCWO in the treatment of aqueous waste are undeniable.
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    Desvios bacharelizantes e atuação em interníveis: um diálogo com formadores de professores de química do IF
    (Universidade Federal de Goiás, 2022-11-30) Silva, Francisca das Chagas Alves da; Mesquita, Nyuara Araújo da Silva;; Mesquita, Nyuara Araújo da Silva; Soares, Marlon Herbert Flora Barbosa; Costa, Lorenna Silva Oliveira; Vilela-Ribeiro, Eveline Borges; Santos, Bruno Ferreira dos
    In a challenging context of tensions and disputes, it was discussed the teacher identity profile of the teacher trainers of Degree in Chemistry at the Instituto Federal do Piauí (IFPI) in its five campuses. It was reflected on the Scientific Field of Chemistry (CCQ), the subfield of chemistry teacher training and the constitution of the IF. In this sense, it is a qualitative research that was guided by the following question: What is the constituted identity of the teacher trainer within the IFPI in terms of the structuring of the Institutes, in terms of the demand for performance as teacher and how does this identity profile influence the intended identity for the graduation? Thus, the general objective of the research is to investigate the process of structuring the teacher identity of the teacher trainers of Degree in Chemistry of the IFPI, considering their training and performance at the different levels of education in which they teach classes at the institution. To meet the objective, it was carried out a historical review of the CCQ to characterize the field and locate teaching in this space. The Chemistry Teaching area discusses the deviations in the graduation that interfere in the training of chemistry teachers and seeks space in the licentiates in the consolidation of the Subfield of Chemistry Teacher Training (FPQ). As a methodological theoretical foundation, this research was anchored in praxiological method of Pierre Bourdieu, in which the concepts of field, habitus, capital and strategy are central to the understanding. In this scenario, it was identified aspects of the teaching profile of a group of 14 chemistry teacher trainers from the five campuses with voluntary participation. The empirical investigation was carried out by means of data collection on the lattes platform of the 14 curricula of these teachers, as well as semi-structured interviews and the analysis of the PPC of the graduations. It was used the theoretical basis of the Critical Communicative Methodology (CCM) in the analysis of the interviews, because its assumptions, based on intersubjective dialogue, reflection and the hierarchical gap between researcher and researched, allowed this research to identify the dimensions that hinder (deviations in the graduation and fragmentation into levels) and transforming dimensions (the change in teacher training legislation and inter-level teaching), which provide a way to overcome the problems of the reality under study. The deviations in the graduation hinder to the structuring of the identity profile of the teacher trainer of the degree and show that the pure scientific capital of the teachers coming from the scientific production is close to the technological subfield of chemistry that has been spreading the chemical habitus in the degree. The trainers in their work and research carry the legacy acquired in the scientific-academic trajectory focused on the chemical habitus that reverberates in their performance through the non-recognition of the spaces of chemistry teaching. The element of fragmentation into levels makes it difficult to perceive the dynamics of t IF to develop an experiential knowledge dimension that influences the way of being, thinking and behaving of teachers. The transformative dimension arising from the change in teacher training legislation configured changes in the PPC and in the graduation, but the legacy of the chemical habitus was identified in the discourse of some trainers. The Inter-level Teaching looks at the configuration of the IF, its influence on the performance of the teacher trainer and contributions to the experiential knowledge that identified a plural, versatile and adaptable teacher according to the dynamics of the institution. Then, it is possible tread a path towards restructuring the teaching identity of the teacher trainer who works in the IF, considering the contributions of the FPQ subfield to this process that reverberates in the professional development of the IF teachers.
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    Reação de Claisen-Schmidt catalisada por carvões ativados de origem vegetal
    (Universidade Federal de Goiás, 2020-03-27) Catharin, Caroline Winter; Chaves, Andréa Rodrigues;; Noda Pérez, Caridad;; Noda Pérez, Caridad; Ostroski, Indianara Conceição; Oliveira, Sérgio Botelho de; Henriques, Cristiane Assumpção; Rosseto, Renato
    Claisen-Schmidt reaction allows chalcones synthesis, which present biological activity of great interest, as anticancer, by acid or basic catalysis. Activated carbons were prepared with vegetable biomass from domestic or industrial waste, as pequi external mesocarp and shells, coffee grounds and malt bagasse by dehydration with sulfuric acid (98%), washed with distilled water until pH 4 and dried. A portion of prepared carbons were subjected to an alkaline treatment with NaOH 2 mol/L solution and washed with distilled water to pH 8 and dried. Additionally, activated carbons from babassu powdered and granulated, obtained by the industrial process of physical activation, were submitted to the same alkaline treatment. Carbons were characterized by scanning electron microscopy (SEM), thermogravimetry (TG), differential thermal analysis (DTA), textural analysis, infrared spectroscopy (FT-IR), X-rays diffraction (XRD), CHNS elemental analysis and determination of acid and basic sites by the Boehm method. The prepared carbons were tested as catalysts on Claisen-Schmidt condensation reaction between Acetophenone and 4-nitrobenzaldehyde using methanol as solvent at room temperature for 24 h. The conversion of acetophenone was evaluated on HPLC. The highest conversion among carbons produced by dehydration was obtained for coffee grounds carbon with basic characteristics, 64.19%. Among carbons with acid characteristics, the best conversion was 61.70%, for carbon obtained from pequi shell. The reuse test of the activated carbon from pequi shell with acidic characteristics for the reaction under study provided a conversion of 46.50%. Among the industrial carbons, the best was the granulated, achieving conversion of 69.26%. The kinetic study of Claisen-Schmidt reaction was carried out with treated industrial granular carbon, as it showed a higher conversion than the pulverized one and less operational difficulties in a continuous reactor. The reaction kinetics of second global order and the rate constants were determined at 35°C and 50°C. The activation energy calculated for this reaction was 18.91 kJ/mol. The conversion in a fixed bed continuous reactor for 1:1 molar ratio of reactants, with acetophenone and 4-nitrobenzaldehyde initial concentration of 0.05 mol/L, achieved 60.23% in 10 min with ascending flow, for a period of 90 min. Another reaction of aldol condensation was evaluated with NaOH-treated granulated babassu catalyst to obtain (1E,4E)-1-(4-nitrophenyl)-5-(2,6,6-trimethyl-1-ciclohexen-1-yl)-1,4-pentadien-3-one. The reaction was conducted between 3 mmol of β-ionone and 2.5 mmol of 4-nitrobenzaldehyde at 27°C and 55°C. After only 1 h of reaction at 55°C the conversion achieved over 4-nitrobenzaldehyde was 63.95%, while at 27°C it was 28.87%. The specific speed constants and activation energy obtained for the reaction demonstrated the production of this compound is strongly affected by temperature. After 4.5 h of reaction the yield achieved was 82%, indicating a great potential for activated carbons from vegetable source in heterogeneous catalysis.
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    A boniteza da implementação da Lei 10.639/03 no ensino de química esperançando criticamente superar os estigmas étnico-raciais do ambiente escolar
    (Universidade Federal de Goiás, 2022-06-07) Moreira, Marilene Barcelos; Benite, Anna Maria Canavarro; Benite, Anna Maria Canavarro; Pinheiro, Bárbara Carine Soares; Mesquita, Nyuara Araújo da Silva; Ferraz, Elzimar Pereira Nascimento; Longhin, Sandra Regina
    The Brazilian educational system, which has trained many generations, has been based on traditional, conservative, alienating models that standardize minds and behavior. These models are characteristics inherited from colonization, which for a long time used the dictates of the Eurocentric monoculture, which validates a single and exclusive "scientific knowledge", excluding from the social dynamics, the knowledge of other people from the educational scenario. Unfortunately, these elements have closed our eyes to the asymmetries and social problems present in the classroom. However, the requirements of Law 10.639/03 brought to education our awakening to ethnic-racial relations, while it taught us to build our "being more". Thinking about the statements of bell hooks on anti-racist education, Paulo Freire on liberating education and the pedagogical interventions developed in the CIATA Collective, we built this thesis seeking to answer: "is it possible to teach Chemistry through an elective subject that has elements of the African Diaspora as a context? We developed the elective discipline "Chemistry in the kitchen: food and the African diaspora" in the school unit CEPAE/UFG, being offered in 2019. We know that there are several instructional materials with anti-racist perspectives for science teaching, but we needed one that embraced the triangulation of chemical knowledge and the three Freirian pillars: culturality, politicality and dialogicity. Thus, we developed our instructional material that was offered, in printed form, to 30 high school students in the 2nd and 3rd grade. All classes were recorded and later transcribed, which we reflected upon in the light of Conversation Analysis. From the actions taken, we bring the reflections of two pedagogical interventions, being that of subtheme 03, African diaspora and carbohydrates as a source of energy (with 118 conversational turns) and that of subtheme 09, the African traditional knowledge in the popular pharmacopoeia of the serried as a context in the identification and conceptualization of substances (with 138 conversational turns). We limited the analysis to these two, because we understand that they already bring enough reflections capable of answering the proposed question. In this research, we present the reasons for the implementation of law 10.639/03 in primary and secondary education; the Freirean perspectives for an anti-racist education; and, the chapter that interweaves the teaching of chemistry, food and African and Afro-Brazilian culture. In the unveiling of the plot, we explain the development (planning and elaboration) of the instructional material for each theme, as well as the reflections, supported by the Freirian pillars (which we call circularity) and by theoretical references of the science/teaching of chemistry and anti-racist education. The data aims to show that a collaborative and contextualized teaching with the students' reality can be a possible path to the construction of an anti-racist and liberating education.
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    Oral squamous cell carcinoma lipid differentiation in gingiva tissue by mass spectrometry
    (Universidade Federal de Goiás, 2022-09-23) Bernardo, Ricardo Alves; Chaves, Andréa Rodrigues;; Chaves, Andréa Rodrigues; Janfelt, Christian; Porcari, Andréia de Melo; Lima, Eliana Martins; Coltro, Wendell Karlos Tomazelli
    Oral squamous cell carcinoma (OSCC) is the most common oral cavity cancer, responsible for 90% of all cancers in the head-neck region, except for non-melanoma skin cancer. A fast, accurate, and cheap diagnosis is required to detect the presence of OSCC in the preliminary stages providing better chances of success in cancer treatment. In general, the diagnosis is performed using proteomics and histological data. However, lipids play a key role in cellular metabolism. Therefore, understanding the lipid differentiation between healthy and cancer tissues could be important to predict biomarkers candidates and improve the diagnosis system. Furthermore, a new methodology for simultaneous RNA and lipid extraction using TRIzol® solution was developed, and the lipid profile in both sample groups was studied. The samples stored in TRIzol® solution were homogenized and submitted to liquid-liquid microextraction (LLME) using chloroform as an extractive solvent. Therefore, the organic phase was collected and submitted to the Bligh &Dyer extraction. The simultaneous RNA and lipid extraction was validated according to the parameters described by the Brazilian Nation Health Surveillance Agency. An analytical curve of tissue in methanol and another one of tissue in TRIzol® solution were performed for method evaluation. The sample solutions were spiked with different concentrations of PC 17:0/17:0 standard solution, and caffeine-(trimethyl-13C) was used as the internal standard and directly infused into the mass spectrometer on positive ion mode. Intra-day and inter-day precision, accuracy, absolute recovery, and matrix effect were evaluated in three concentration levels in replicate (n=5). Limits of detection and quantification were estimated in the order of ng mL-1 with good linearity (r² >0.99), precision and accuracy (<15%), and absolute recovery values ranging from 90 to 110%. The mass spectra were submitted to the Global Natural Product Social Network (GNPS) platform for peak annotation. The partial least-square discriminant analysis (PLS-DA) was performed in all samples clustering the healthy samples and separating them from the cancer ones. The PLS-DA revealed that 15 lipids were responsible for describing the healthy group in the positive ion mode, while 8 lipids described the cancer one. In the negative ion mode, 10 lipids described the healthy group, while 10 lipids described the cancer one. Furthermore, cryosections of gingiva tissue (healthy and cancer ones) with 10 µm thickness were analyzed by matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) to investigate which lipids pointed by the PLS-DA delimit the cancer region. The MALDI-MSI analyses showed that the lipids responsible for OSCC group classification are more abundant in the cancer tissue compared to the healthy one. The extraction methodology reported here, and the MALDI-MSI as confirmation technique are adequate for classification of OSCC samples regarding lipid content.
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    Microdispositivo de poliestireno-toner rotacionalmente controlado por um hand-spinner e aplicações no diagnóstico molecular de doenças infecciosas
    (Universidade Federal de Goiás, 2022-04-14) Oliveira, Kézia Gomes de; Duarte, Gabriela Rodrigues Mendes;; Duarte, Gabriela Rodrigues Mendes; Chaves, Andrea Rodrigues; Coltro, Wendell Karlos Tomazelli; Bailão, Alexandre Melo
    Infections caused by the new coronavirus (SARS-CoV-2) and arthropod-borne viral infections such as dengue, zika and chikungunya have become a severe public health problem. As all diseases have a significant social impact, the accurate and rapid diagnosis of the infection can be instrumental in treating and adequately controlling the disease. Loop-mediated isothermal amplification (LAMP) emerged in 2000 as an essential alternative to simplify the diagnostics of infectious diseases. An advantage of LAMP is that it allows a straightforward reading of the final result through visual detection. However, this step must be performed with caution to avoid contamination and false-positive results, especially in cases where there is a need to open the tube. In this sense, LAMP performed on microfluidic platforms can minimize false-positive results and have potential for point-of-care applications. Here, we describe a polystyrene (PS-T) centrifugal microfluidic device manually controlled by a hand-spinner for molecular diagnosis of COVID-19, dengue, zika and chikungunya by RT-LAMP, with integrated and automated colorimetric detection. The confirmatory and discriminatory on-chip RT-LAMP test was performed with two types of detection: i) automated addition of SYBR Green fluorescent dye post-amplification (RT-LAMP-SG), and ii) addition of the pH indicator, cresol red, pre-incubation (RT-LAMP-CR). RT-LAMP-SG amplification was performed in a microchamber with a capacity of 5 μL, and the SG was inserted in another chamber with a 3 μL. The reaction was thermally controlled with a thermoblock. At the end of the incubation time (10 min), the detection was performed directly on the device by visual detection after the microdevice spun with a hand-spinner. Our results for the endpoint detection system for LAMP (RT-LAMP-SG) demonstrate that it is possible to detect SARS-CoV-2, DENV-1, ZIKV and CHIKV in the microdevices with a detection limit of approximately 10-3, 660, 30 and 48 RNA copies μL-1 respectively. Clinical samples of patients infected with COVID-19 were tested using our RT-LAMP protocol as well as by conventional RT-qPCR, demonstrating comparable performance to the CDC SARS-CoV-2 RT-qPCR assay. For the RT-LAMP-CR amplification, only the detection of arboviruses was evaluated and presented a detection limit of 1050, 15 and 72.5 copies per μL for detecting DENV-1, ZIKV and CHIKV, respectively. Devices in CD setup were successfully handled performing the three tests simultaneously (dengue, zika and chikungunya) for both detection methods (RT-LAMP-SG and RT-LAMP-CR). The methodologies designated in this study represent simple methods for rapid molecular diagnostics of infectious viral diseases on disposable microdevices, ideal for point-of-care test (POCT) systems.
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    Avaliação da composição química de indivíduos adultos de araucaria angustifolia (Bert.) kutz. através da RMN aliada a quimiometria visando a distinção sexual
    (Universidade Federal de Goiás, 2016-12-15) Oliveira, Gerlon de Almeida Ribeiro; Lião, Luciano Morais;; Lião, Luciano Morais; Barison, Andersson; Novotny, Etelvino Henrique; Zanette, Flávio; Venturoli, Fábio
    Araucaria angustifolia, popularly known as araucaria or pine of Paraná, is an endemic conifer in the Brazilian southern and southeastern. The preserved areas represent source of income to a great number of families of collectors, due to the interest of the population for the so called “pinhão”, the seed of the araucaria. Araucaria is a dioecious plant, and only the female plants produce the “pinhão”. Determining the sex of the seedlings would be interesting so that a higher number of females than males could be planted, which would increase the production of pinhão and would make this species more attractive for reforestation purposes. There is no technique for knowing the sex of the seedlings before they express their sexuality, which occurs between fifteen and twenty years after planting. The objective of this study was to evaluate the possibility of using nuclear magnetic resonance (NMR), mass spectrometry (MS), and infrared spectroscopy in the non-targeted metabolomic approach for the sexual determination of adult individuals of araucaria. 80 samples of adult plant needles were collected in the state of Paraná, Brazil. The needles were macerated with liquid nitrogen and extracted with deuterated chloroform (NMR), or methanol (MS). Several pre-treatments were evaluated, as well as different non-supervised (clusters analysis and principal component analysis, PCA) and supervised multivariate techniques (partial least squares discriminant analysis – PLS-DA, linear discriminant analysis, LDA, after selection of variables by genetic algorithm). Using the strategy described herein, the chemometric models indicated only some trends of separation of the groups according to sex, which, however, were not generalizable.
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    Intensidades vibracionais fundamentais de moléculas em estados eletronicamente excitados: SAC-CI e QTAIM/CCFDF
    (Universidade Federal de Goiás, 2017-06-30) Martins, Gabriel Rodrigues; Oliveira, Anselmo Elcana de;; Oliveira, Anselmo Elcana de; Gargano, Ricardo; Camargo, Ademir João; Castro, Marcos Antônio de; Guimarães, Freddy Fernandes
    The Charge–Charge Flux–Dipole Flux (CCFDF) model using QTAIM parameters at the SAC-CI/cc-pVTZ calculation level was used to estimate XO2 (X = O, S, Se, Te) and H2X (X = O, S, Se, Te) fundamental vibrational intensities for ground and 15 low-lying electronic excited states. Charge flux, dipole flux, and its interactions were the most important contributions to the Q3 (for XO2) and Q2 (for H2X) modes of infrared intensities. Electronic Location Functions (ELFs) for H2X emphasize changes between dissynaptic and central atom monosynaptic valence basins when changing from ground to electronic excited states. XO2 ELFs, on the other hand, present electron migration to monosynaptic valence basins for both central and terminal atoms. Atomic polar tensor elements after geometry reorientation show that the largest variations in the CCFDF contributions are related to the charge flux. The results from the present work/Thesis indicate that QTAIM/CCFDF approach can be employed to interpret infrared intensities not only for ground, but also for electronic excited states.
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    Contribuição ao estudo metabolômico de espécies do gênero Cnidoscolus (Euphorbiaceae) da região do Cerrado e da Caatinga
    (Universidade Federal de Goiás, 2022-04-06) Martins, Marcos Pereira; Kato, Lucilia;; Kato, Lucilia; Lião, Luciano Morais; Severino, Vanessa Gisele Pasqualotto; Lemes, Geralda de Fátima; Paiva, Joseilson Alves de
    The genus Cnidoscolus belongs to the Euphorbiaceae family, is popularly known as cansanção or favela, and is distributed in several countries in America. In Brazil, this genus is mainly present in the Caatinga phytogeographic domain and has several species widely used by traditional communities. However, there are few chemical and pharmacological studies on this genus and there are no works description involving the annotation of compounds by Molecular Networking. In order to expand the chemical knowledge about the species C. bahianus, C. urniger and C. vitifolius, Nuclear Magnetic Resonance (NMR) and high performance liquid chromatography coupled to electrospray ionization mass spectrometry (HPLC-ESI-MS/MS), principal component analysis (PCA), analyzes were performed involving extracts from leaves and stems, and some metabolites were isolated by filter column chromatography. The antimicrobial activities of C. bahianus, C. urniger and C. vitifolius extracts against Escherichia coli and Staphylococcus aureus strains were evaluated to determine the Minimum Inhibitory Concentration (MIC). The PCA of the 1H NMR data of the extracts revealed that the chemical profile of the species is similar. The analysis of the metabolic classes of the compounds from Cnidoscolus species by HPLC-IES-MS/MS (positive and negative modes) with consequent construction of molecular networking of the studied species led to the dereplication of phenolic compounds with the annotation of 40 flavonoids (class of flavonols, flavanols, flavones and flavanones) and 4 hydroxycinnamic acids. The metabolites isolated by filter chromatography were characterized by NMR as belonging to the steroid class (sitosterol, stigmasterol, campesterol and fucosterol). The ethanolic extract of C. bahianus leaves showed moderate antimicrobial activity and the others showed no activity for the tested strains.
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    Síntese, avaliação do potencial antitumoral in vitro e docking molecular de novas imino - chalconas candidatas a inibidoras de CDK2
    (Universidade Federal de Goiás, 2022-02-11) Anjos, Murilo Machado dos; Alonso, Christian Gonçalves;; Oliveira, Guilherme Roberto de;; Oliveira, Guilherme Roberto de; Chagas, Rafael Pavão das; Gomes, Marcelo do Nascimento; Costa, Maísa Borges; Pérez, Caridad Noda
    The search for new active compounds is a line of research widely studied in the area of organic chemistry. Within this niche, computational tools, such as molecular docking, gain great importance for shortening and being able to assertively predict the discoveries of new drugs, as well as the repositioning of these. Among the classes of natural products that receive enormous attention in this field, the chalcones and their derivatives stand out, as they have diverse applicability and have an attractive structural scafford for structural modifications. The objective of this work was the synthesis of derivatives of chalcones, evaluation of the profile of tumor inhibition against the cell lines SNB-19 (Glioblastoma), PC-3 (Prostate), HCT-116 (Colon) and HL-60 (leukemia) and the search for biological targets for the synthesized products, with the purpose of applying the molecular docking process. Seven compounds were synthesized with yields ranging from 25% to 43%, where 5 of these were not published (M1, M4, M5, M6 and M7). The synthesized imino chalcones were tested in vitro against the four cancer cell lines showing an inhibition profile above 75% for all lines, especially the HL-60 line where all compounds showed an inhibition profile above 99%. Compound M4 had the lowest IC50 value, 5.5 µM, for the HL-60 strain. The identification of molecular targets was performed using the PharmMapper platform, where two possible targets were identified, these being the proteins DAPK3 and CDK2. The docking process was validated using the redcoking of the co-crystallization ligands, with the parameters previously defined, where the validity of the process was demonstrated, noting a mean square deviation (RMSD) value close to the crystallographic data, both smaller than 2 Å, where the value found for CDK2 was 0.099 Å. The docking results indicate that the imino-chalcones had a higher affinity for the CDK2 protein, where the compound M4 had the best affinity value (-10.0 Kcal/mol), interacting with some key residues of the CDK2 enzyme by hydrogen bonding with Leu83 and π-anion with Asp145. The ADME profile shows that imino-chalcones have good gastrointestinal absorption, with the exception of compounds M1 and M3. The compounds inhibit CYP3A4, with the exception of M1, in addition to being substrated from p-glycoprotein (Pg-p), minus M2, indicating that an optimization of the structures is necessary to improve their ADME properties.
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    Hibridação molecular de chalconas e análogos de neolignanas com potencial atividade antineoplásica
    (Universidade Federal de Goiás, 2021-12-15) Fernandes, Fernanda de Sousa; Alonso, Christian Gonçalves;; Oliveira, Guilherme Roberto de;; Oliveira, Guilherme Roberto de; Noda Pérez, Caridad; Gomes, Marcelo do Nascimento; Andrade, Fabiano Molinos de; Lemes, Geralda de Fáma
    The search for bioactive chemical substances, both natural and synthetic, starts from the same assumption: the reduction of the side effects caused by the drugs and increasing the effectiveness of the drug to its biological target. Same that several researches have been conducted for the synthesis of chalcones, neolignans and their analogues, there is not, so far, in the main databases used in this research, studies that have used these two classes of molecules coupled in the form of a hybrid on different therapeutic targets. The first stage of work consisted of synthesizing the reaction precursors, including 2-bromo-1-phenylethanone and 22 chalcones (2-hydroxychalcones, 3-hydroxychalcones and 4-hydroxychalcones) in which yields ranging from 15 to 100% were obtained. In possession of the different chalconas, the study of the reaction conditions that gave rise to the new analogue hybrids of 8,4'-oxyneolignans. Of the tested chalcones, those that showed promising results were the 3-hydroxychalcones and the 4-hydroxychalcones, obtaining 14 new hybrid molecules in yields ranging from 18 to 83%. The hybrid molecules synthesized had their properties biological agents evaluated for cytotoxic effects and the concentration that caused 50% of cell growth inhibition (IC50) in tumor cell lines of human glioblastoma (SNB-19), colon (HCT-116), prostate (PC-3) and leukemia acute promyelocytic (HL-60). The results of the cytotoxicity assay showed that 12 compounds (among the 14 tested) showed a percentage of inhibition of promising cell growth (≥75% cell inhibition). Compounds 67-80 were selected and the IC50 assay was evaluated revealing a moderate inhibition profile for compounds that present the chalcone moiety with groups that decrease the electronic density of the ring (deactivators), with compound 73 having the lowest IC50, for this methodology. Structural modifications of analogous compounds do not led to significant increases in cytotoxic activity when compared to the drug reference doxorubicin.
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    Estudo fitoquímico de Lomatozona artemisiifolia Baker (Asteraceae), uma espécie endêmica do Cerrado, através de cromatografia líquida acoplada à espectrometria de massas e quimiometria
    (Universidade Federal de Goiás, 2021-10-06) Wakui, Vinícius Galvão; Kato, Lucilia;; Kato, Lucilia; Queiroz Júnior, Luiz Henrique Keng; Oliveira, Cecilia Maria Alves de; Alcantara, Glaucia Braz; Lago, João Henrique Ghilardi
    The Brazilian Cerrado is recognized for its biodiversity and the presence of several endemic species with a great potential for biological activities. The specie Lomatozona artemisiifolia Baker is endemic from Cerrado of the Brazilian Midwest region and it is currently endangered. The in vitro micropropagation studies were conducted in previous works, a technique that allows its production in the laboratory looking for conservation on this biome. Thus, based on the biological activities already reported in the literature for other species of Asteraceae endemic to the Cerrado, this work reports the phytochemical study of L. artemisiifolia and a comparison between in vitro and the native species of this biome. The observation of missing chemical study with species of the genus Lomatozona, the major compounds labdan-8-ol-15-il (1), labdan-8,15-diol (2), 8-hydroxylabdan-15-oic acid (3), chrysosplenetin (4), paquipodol (5), quercetagetin-3,5,6,3',4'-pentamethyl ether (6) and oxyanin B (7), were isolated. Then, the extracts of L. artemisiifolia from native and in vitro species were studied by LC-ESI-MS/MS and they have been compared by the chemometric analysis, thats allow to observe significant differences between the ethyl acetate extracts, that was related to its foliar surface content. The molecular network analyzes were conducted in order to annotate the other compounds present in this species, leading to dereplication of several subclasses of flavonoids. The chemometric analysis together with the molecular network analysis allowed us to identify the metabolite subclasses whose production is influenced by the conditions of field growth and in vitro micropropagation. It was observed that native and in vitro species are mainly differentiated by the chemical content secreted by glandular trichomes, distributed over the foliar surface of this species, thus indicating possible abnormalities in the development of vegetal structures in the plant obtained by micropropagation. The extracts from Lomatozoma were evaluated on the control of the phytonematode Pratylenchus brachyurus based on the metabolite classes identified in L. artemisiifolia. However, the results indicated a low potential for the nematicide activity.
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    Estudo da atividade catalítica do óxido de grafite em reações orgânicas
    (Universidade Federal de Goiás, 2021-12-14) Naves, Raquel Ferreira; Alonso, Christian Gonçalves;; Oliveira, Guilherme Roberto de;; Oliveira, Guilherme Roberto de; Silva, Valter Henrique Carvalho; Chagas, Rafael Pavão das; Perez, Caridad Noda; Costa, Maísa Borges
    Graphite oxide (OGt) is characterized as graphite sheets with randomly distributed aromatic regions (sp2 carbon atoms) and oxygenated aliphatic regions (sp3 carbon atoms); has different functional groups such as hydroxyl, epoxy and carboxyl. The presence of these groups confers an acidic character to the material and, due to its biocompatibility, easy reuse, it can be considered a promising heterogeneous catalyst. Thus, we sought to use graphite oxide as an acid catalyst for the following organic reactions: Pechmann, reaction of disubstituted benzimidazoles, Mannich and Biginelli-like. To obtain graphite oxide, the Hummers method was used, in which graphite is oxidized involving a mixture of sodium nitrate, potassium permanganate and concentrated sulfuric acid; however, the methodology is a time-consuming and low-yield process. Thus, the graphite oxide was characterized by X-ray diffraction, IR spectroscopy, thermogravimetic analysis and by electron microscopy, which allowed to evaluate the oxidation process of graphite in graphite oxide. In this study, the reactions were analyzed in many parameters, such as: temperature, stoichiometric ratio, solvents, and amount of catalyst. Thus, when testing graphite oxide in these reactions, it was observed that OGt presented different behavior in each type of reaction; it was found that for the disubstituted benzimidazoles only 30 mg were needed to obtain a yield greater than 80%, while for the Biginelli-like reaction 300 mg was used and a yield below 80% was obtained. However, conditions were sought in which the reactions occurred in the absence of solvent, in order to make the processes environmentally friendly with the use of graphite oxide as a heterogeneous solid catalyst. Furthermore, the variation of substrates was evaluated for all reactions, which allowed us to observe that the best yields occurred with substrates in the presence of electron activating groups, while for the Pechmann, Mannich and Biginelli-like reactions there was no formation of products with an electron-withdrawing group -NO2. All products were characterized by 1H and 13C NMR and were identified by comparison with the spectra reported in the literature.
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    Análise de síntons intermoleculares de bases N-heterocíclicas e suas correlações com propriedades óticas
    (Universidade Federal de Goiás, 2021-12-17) Valdo, Ana Karoline Silva Mendanha; Martins, Felipe Terra;; Martins, Felipe Terra; Guimarães, Freddy Fernandes; Nakahata, Douglas Hideki; Santana, Ricardo Costa de; Araujo Neto, João Honorato de
    One of the aims of crystal engineering is the analysis of synthons. The understanding of synthons formation allows modifying them to obtain chemical and physical properties of interest. Among those properties, structure dependents, are optical and electronic properties. The second harmonic generation (SHG) is one example of nonlinear optics phenomena and has a great potential aaplication. In this area, several organic compounds, such as nitrogenous aromatic ones, show SHG. Although robust synthons exist, their modification is delicate, since various parameters induce their formation. Moreover, the SHG has a requirement of inversion center absence in the structure. In this context, guiding structure to specific symmetries are still a crystallographic hard task. In this work the synthons of monoprotonated nitrogenous aromatic compounds salts were analyzed. The salts were synthesized throughout the reaction of nitrogenous compounds (dissolved in isopropanol) with organic and inorganic acids. The used compounds belong to the classes of pyrimidines and pyrazines. After the synthesis, the acidified solutions were submitted to crystallization using the slow evaporation technique. The single crystals had their X-Ray Diffraction data collected. Yet, reflectance diffuse spectroscopy data were collected for some samples. Further, calculations of electronic structure to obtain geometric optimization and spectra absorption data were performed. These calculations were done with density functional theory (and time-dependent density functional theory), with the functional M06-2X or B3LYP and the base 6-31G** or Def2-TZV. In this study fifteen unpublished structures were obtained, among which only one was solved in a noncentrosymmetic space group. The analyses of synthons in all structures revealed two tendencies. The first was observed for the structures obtained from 2-aminopyrazine. In those structures, the protonation of 2-aminopyrazine nitrogen (from aromatic ring) not depended on exclusively of 𝑝𝑘𝑎 from compounds, but also has relation with the final synthons. Accordingly, it was possible to noted that not only a chemical propriety dictates the protonation in the formation of a crystalline medium. Beyond that, the energy of finals intra and intermolecular interactions were essential to understand this result. The other tendency was verified for the compound derived of 2-aminopyrazine substituted by halogen atoms in the aromatic ring, in which, the synthons for the aromatic compounds with or without halogen atoms were the same. Thus, it was observed that a structural modification as an insertion of a halogen atom did not alter the interactions pattern in aromatic compounds. Regarding the physical properties, the direct band gap value for some nitrogenous compound was determined experimentally. Finally, we related the approximationof theoretical and experimental data on electronic transition with the energy of synthons or interactions for a set of atoms present in the structures. For some data, we observed that the greater the stability of the interactions involved, the closer were the theoretical data to the experimental one for the electronic transitions. However, this did not extend to all datasets analyzed in this work.