Programa de Pós-Graduação em Química - PPGQ/ICEN

URI Permanente desta comunidadehttps://repositorio.ufpa.br/handle/2011/4046

O Programa de Pós-Graduação em Química (PPGQ) do Instituto de Ciências Exatas e Naturais (ICEN) da Universidade Federal do Pará (UFPA). Oferece oportunidade para a formação de Mestres e Doutores nas áreas de Química Orgânica, Físico-Química, Inorgânica e Analítica.

Navegar

Agora exibindo 1 - 10 de 10

Acesso aberto (Open Access)
Estudo computacional de arilpiperidina e arilpiperazina como inibidores de tirosinase: aplicações cosméticas e terapêuticas
(Universidade Federal do Pará, 2025-04-08) BENTES, Beatriz Alves; SILVA, José Rogério de Araújo; SILVA, Jerônimo Lameira; http://lattes.cnpq.br/7711489635465954
Tyrosinases (TYR) catalyze the oxidation of phenols and catechols, playing a crucial role in melanogenesis, which regulates melanin production and provides protection against UV radiation. However, pigmentation-related disorders drive the search for effective TYR inhibitors. Compounds such as hydroquinone, arbutin, and kojic acid have limitations, highlighting the need for new inhibitors. In this study, arylpiperidine- and arylpiperazine-based compounds demonstrated potent inhibitory activity against TYR. Computational analysis included molecular docking, molecular dynamics (MD) simulations, and binding free energy calculations using the Linear Interaction Energy (LIE) method, revealing a strong correlation with experimental affinity data. To enhance the understanding of structure-activity relationships (SAR), Free Energy Perturbation (FEP) transformations were performed for selected ligand pairs. Additionally, Density Functional Theory (DFT) calculations were applied to inhibitors L04 and L19, enabling the determination of electronic descriptors and frontier molecular orbitals. The inhibitors interact with TYR mainly through electrostatic interactions with the copper ion and van der Waals forces with critical residues such as Phe197, Pro201, Val218, Asn205, and Arg209. These findings are promising for both cosmetic and therapeutic applications, enabling the development of skin-lightening agents to treat melasma and sunspots, as well as potential treatments for hyperpigmentation-related diseases and melanomas. The development of more selective inhibitors with lower toxicity may expand the clinical and cosmetic use of these compounds, offering safer and more effective alternatives for melanin production modulation.
Acesso aberto (Open Access)
Estudo químico e atividades biológicas dos extratos do fungo actinomucor elegans accc18.1a endofítico de rhizophora mangle l. (rhizophoraceae)
(Universidade Federal do Pará, 2024-02-26) PADILLA, Kathia Raquel Murillo; MARINHO, Patrícia Santana Barbosa; http://lattes.cnpq.br/4826647905254039; HTTPS://ORCID.ORG/0000-0002-9368-8574; MARINHO, Andrey Moacir do Rosário; http://lattes.cnpq.br/2511998363000599; https://orcid.org/0000-0002-8981-0995
The study of underexplored natural sources, especially in the Amazon region, has gained significance in recent years. Considering the Amazon as the largest forest in the world, it is notable that many species still remain undiscovered. In this context, research on secondary metabolites of endophytic fungi has sparked growing interest in the scientific community, driven by the potential these microorganisms hold in the field of health. Microorganisms have been a rich source of bioactive metabolites with various applications such as agrochemicals, antibiotics, immunosuppressants, antiparasitic, and anticancer agents. The aim of this study was to contribute to the investigation of endophytic fungi in mangrove plants of the Brazilian Amazon through the isolation and identification of compounds with antimicrobial, allelopathic, and anticancer activities from the fungus Actinomucor elegans AcCC181A, which was isolated as an endophyte from the plant Rhizophora mangle L. (Rhizophoraceae). Using chromatography techniques, the phenolic compounds tyrosol (S-1), 4-hydroxyphenylacetic acid (S-2), 4-formylphenyl 2-phenylacetate (S-3), and phenylacetic acid (S-4) were isolated. From tyrosol, the substances 4-(2-acetoxyethyl)-phenylacetate (S-5), 4-(2-(butyryloxy)ethyl)- phenylbutyrate (S-6), and 4-(2-(benzoyloxy)ethyl)phenylbenzoate (S-7) were obtained through structural derivatization. The structures of the substances were elucidated using Nuclear Magnetic Resonance (NMR) and Mass Spectrometry (MS) techniques. The substances and crude extract were tested against the bacteria E. coli, Bacillus subtilis, S. typhimurium, S. aureus, and Xanthomonas axonopodis pv. passiflorae, showing antimicrobial activity results. Cytotoxicity and cell viability assays of the isolated substances S-1, S-2, and S-3 were also performed. All tested substances demonstrated potential cytotoxic activity on gastric cancer cell lines. Additionally, the allelopathic potential of the crude extract was evaluated, showing activity with lettuce seeds. It is important to note that compounds S-6, S-3, and S-7 are being tested for the first time in antimicrobial assays. Furthermore, it is relevant to emphasize that this study represents the first report of antimicrobial assays conducted with the substances isolated in this work against the bacteria Xanthomonas axonopodis pv. passiflorae.
Acesso aberto (Open Access)
Influência do ph do banho e da densidade de corrente no comportamento capacitivo de eletrodos de mno2 obtidos por eletrodeposição anódica
(Universidade Federal do Pará, 2025-01-30) RENTE, Arthur de Farias Silva; NOCE, Rodrigo Della; http://lattes.cnpq.br/3734170057844016
MnO₂ electrodes are obtained by anodic electrodeposition on stainless steel substrate at room temperature from a 0.1 M manganese sulfate bath, under different current densities, ranging from 200 µA·cm⁻² to 5 mA·cm⁻² (galvanostatic mode), and pH values from 2 to 6. The material morphology is analyzed by scanning electron microscopy, revealing compact, homogeneous, and two-dimensional film deposition, with the presence of microcracks that provide active sites for the incorporation of sodium sulfate (Na₂SO₄) electrolyte ions, enhancing the material's specific capacitance. At low current densities, such as 200 and 500 µA·cm⁻², the formed film is homogeneous, while increasing the current density to 2 mA·cm⁻² results in cracks on the material's surface. Morphological changes are also identified as a function of pH: near neutrality (pH 6), cracks become evident, whereas in more acidic pH levels, such as 2 and 3, the structure remains uniform. At pH 4, an irregular structure is observed. The structure of the formed films, analyzed by by X-ray diffraction, reveals the presence of the alpha (α) phase under all studied conditions, regardless of the applied current density and bath pH. Electrochemical characterization of the films, carried out using cyclic voltammetry and charge-discharge curves (chronopotentiometry), indicates a working potential window of 1.1 V and specific capacitance values ranging from 13 to 371.8 F·g⁻¹, depending on the applied current density and bath pH. The highest specific capacitance value is obtained at a current density of 2 mA·cm⁻² and pH 4.
Acesso aberto (Open Access)
Intercalação do ibuprofeno em hidróxidos duplos lamelares: caracterizações físico-químicas e avaliações biológicas
(Universidade Federal do Pará, 2016-10-14) SOUSA, Paulo Robson Monteiro de; ALVES, Claudio Nahum; http://lattes.cnpq.br/8315600067791313; SILVA, Jerônimo Lameira; http://lattes.cnpq.br/7711489635465954
Ibuprofen-intercalated layered double hydroxides (LDH-IBU) have been successfully synthesized via a co-precipitation method with a nominal [Al3+]/[Mg2+] ratio of 0.5 and a variable molar IBU/([Al3+]+[Mg2+]) ratio of 0, 0.15, 0.18, 0.24, 0.36 and 0.72. After an accurate determination of the composition, the nature of the intercalated species and the effective intercalation yield from NO3 - to IBU, it is shown that the synthesis route used allows a good control of the quantity of intercalated IBU within the LDH framework. This results in different samples with full or partial IBU intercalation in the interlayer space in exchange of nitrate anions. The analysis of the X-ray diffraction basal reflections reveals that the intercalation of IBU in the framework only increases the basal distances with no alteration of the brucite-type layers. Also, a computational study used to model the positions and shapes of the basal reflections showed that the structure of the non-fully intercalated compounds follows a random interstratification scheme. Finally three samples ranging from slightly to fully IBU-intercalated galleries were selected for preliminary in vivo assays. These tests showed a strong tendency that after 24 hours the low yield of IBUintercalated compounds are almost as efficient as the fully intercalated sample.
Acesso aberto (Open Access)
Investigação de metabólitos secundários de folhas de Derris urucu (Killip et Smith) Macbr. com atividades biológicas
(Universidade Federal do Pará, 2009-06-30) LÔBO, Lívia Trindade; SILVA, Milton Nascimento da; http://lattes.cnpq.br/6742390457977989; ARRUDA, Mara Silvia Pinheiro; http://lattes.cnpq.br/8047078292358267
Derris urucu, belonging to the family Leguminosae / Fabaceae, is popularly known as “timbó”. The roots of this species are commonly used as pesticides and poison to fish. From Derris genus many phytochemical studies have been reported, the roots being of the most studied part from the plants of this genus. The name “timbó” is most general for the species Derris urucu and Derris nicou, which are the species that produce, in their roots, rotenoids such as rotenone and deguelin, from which derives the importance of these plants. The extracts, and the substances isolated from this genus are responsible for a wide range of biological activities, mainly the insecticidal activity. From the ethanolic extract of leaves of D. urucu, twelve compounds were isolated and purified by High Performance Liquid Chromatography: five stilbenes, six dihydroflavonols and one flavanone. The structural identification was based on the mass, 1H and 13C NMR spectrometric analysis and two dimensional NMR, beyond comparison with literature data . The ethanolic extract of leaves of D. urucu was submitted to bioassays to avaluate the allelophatic potential, presenting relevant percentage of inhibition of seed germination and development of weeds in pastures. Aiming to detect the substances responsible for allelophatic activity, three stilbenes and three dihydroflavonols were selected and submitted to bioassays of inhibition of germination and development of the radicle and hypocotyl of weeds. The allelophatic tests were performed with the substances isolated and with the combination of them, aiming to assess the synergism between them, but the magnitude of inhibition observed was very low. By other side, when the substances were tested in mixtures there was a significant increase in the percentage of inhibition, so these substances in mixtures, can be considered promising for future studies involving allelophatic activity. An other test was carried out with the isolated compounds. Three stilbenes and five dihydroflavonols were evaluated for DPPH radical scavenging activity (antioxidant activity). In this bioassay, was not observed a significant antioxidant activity, justified by the analysis in the structures of the substances tested.
Acesso aberto (Open Access)
Materiais de interações biocarvões/latossolo: caracterização química e físico-química
(Universidade Federal do Pará, 2019-04-17) MACHADO, Marcelly Christian Galvão Rodrigues; MORAES, Milena Carvalho de; http://lattes.cnpq.br/9699850614353792; LEMOS, Vanda Porpino; http://lattes.cnpq.br/1829861620854008
The present study aims to obtain materials from thermochemical interactions biochars-latosoil and to evaluation its chemical and physicochemical properties inrelation to those indicated in high fertility soils. The key importance of this study involves: characteristics indicative of soil with high organic matter stability, as to those indicated for archeological black earth (ABE), due to the structural properties from crystalline and amorphous materials, associated to the organic aggregates, considered natural adsorbent in soils. The sources of biochar were leaves of cinnamon, cacau, cashew and ipê trees and to those for soil was latosoilsample fromthe Caxiuanã region/ Brazil-Pará. The characterization of the materials was performed based on analysis by spectral analytical methods [XRD, FTIR, EDS and MIRO-RAMAN].The results from XRD indicatedspecially characteristics of organic compounds, represented by hexagonal and rhombohedral graphites, turbostratic graphite and graphite oxide. Based elementaryanalysis were obtained atomic ratio O/C corresponding to carbonaceous materials with high aromaticity. Micro-Raman spectra shown bands D e G corresponding to HPA´s pyrene and naphthalene. The following conclusions were obtained: the materials from thermochemical interactions biochars-soil presents chemical and physicochemical properties corresponding to the organic aggregates common in soil with high stability; the presence of HPAs into materials shoud be considered negativefor to use biochars into soils, due to the possibility of contamination of the soil and groundwater.
Acesso aberto (Open Access)
Produção de biodiesel metílico e etílico de oleaginosas Amazônicas: caracterização físico-química e estudos térmico e cinético
(Universidade Federal do Pará, 2016-01-29) LIMA, Rogério Pereira; ROCHA FILHO, Geraldo Narciso da; http://lattes.cnpq.br/7580236895339455
This study aimed to synthesize methyl and ethyl biodiesel from six amazonian species of vegetable oils and fat through the transesterification reaction process using alkaline homogeneous catalysis, determine the heat capacity values of oils and methyl and ethyl biodiesel by differential scanning calorimetry (DSC) in the temperature range of 55 to 195°C, and correlate with information estimated by the group contribution method, to investigate the thermal stability of oils and biodiesel produced by thermogravimetric analysis (TG/DTG) and perform kinetic study of the decomposition thermal of biodiesels using the Ozawa method. Classic physicochemical analysis for the characterization the vegetable oils and the biodiesel synthesized samples were used. The results for the physicochemical properties of methyl biodiesel samples were consistent with the values specified by the Resolution No. 45 of 2014 of the National Agency of Petroleum, Natural Gas and Biofuels (RANP 45/14). The results of heat capacity determined by DSC showed that the methyl biodiesel pracaxi showed the highest values, while for ethyl, it was observed for the biodiesel buriti, andiroba and pracaxi. Most heat capacity data obtained for the methyl and ethyl biodiesel determined by DSC and by the group contribution method were satisfactory, as they showed smaller relative deviations or equal to 15% and showed good correlation coefficients ranged from 0, 8617 to 0.9947. The studies on the thermal stability by thermogravimetric analysis indicated that the oils and fat were stable in the temperature range of 110 to 220°C, in inert atmosphere and, in an oxidizing atmosphere, were thermally stable to 130 at 165°C. All the synthesized biodiesel samples is degraded at temperatures up to 150°C, which is highly volatile, a very important feature for the application in diesel engines. The kinetic study of the thermal decomposition of the methyl and ethyl biodiesel met activation energy values ranging from the 46.23 124.93 kJ.mol-1 and showed that the ethyl biodiesel were more stable than the methyl biodiesel.
Acesso aberto (Open Access)
Síntese de biodiesel utilizando catalisador bifuncional baseado em ferrita com óxido metálico suportado
(Universidade Federal do Pará, 2021-07-23) GONÇALVES, Matheus Arrais; CONCEIÇÃO, Leyvison Rafael Vieira da; http://lattes.cnpq.br/7467898936995220
In this study, a solid magnetic acid catalyst MoO3/SrFe2O4, composed of molybdenum oxide (MoO3) supported on strontium ferrite (SrFe2O4), was synthesized and applied in the transesterification of waste cooking oil (WCO). The catalyst was characterized by acid-base titration method in order to determine Surface acidity, Thermogravimetric analysis (TG/DTG), X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), Energy dispersion X-ray spectroscopy (EDS) and Vibrating sample magnetometry (VSM) techniques. A central composite design of centered face 24 (FCCD) and a mathematical model was developed in order to describe the behavior of the ester content as a function of the independent variables temperature, alcohol:oil molar ratio, catalyst dosage and time reaction. The mathematical model (R2=0.9900) was validated and showed a relative error below 5% between the experimental and predicted values. Using linear regression methods and response surface methodology (RSM) the conditions of biodiesel synthesis reaction were optimized and 95.4% conversion into esters was obtained from the use of the reaction temperature of 164 °C, alcohol:oil molar ratio of 40:1, catalyst dosage of 10% and reaction time of 4 h . The catalyst showed high reusability, since it was possible to use it in 8 reaction cycles which it is an indication of its good prospectus for development and application as bifunctional catalyst.
Acesso aberto (Open Access)
Síntese de catalisador heterogêneo magnético básico aplicado no processo de produção de biodiesel
(Universidade Federal do Pará, 2023-08-30) SANTOS, Hiarla Cristina Lima dos; CONCEIÇÃO, Leyvison Rafael Vieira da; http://lattes.cnpq.br/7467898936995220
This research focus on the development of a basic magnetic heterogeneous catalyst, using, for the first time, NaAlO2 as an active species supported in a magnetic material, CuFe2O4, being highly stable and effective to produce value-added products, such as biodiesel. With this purpose, a series of catalysts (x-NaAlO2/CuFe2O4) have been successfully synthesized by means of conventional and low-cost methods, such as coprecipitation and impregnation, each one being assessed in the soybean oil transesterification reaction. The features of the 25-NaAlO2/CuFe2O4 catalyst with the higher performance have been elucidated through techniques such as basicity by acid-base titration method, XRD, FTIR, SEM, EDS, TG/DTG and VSM. To optimize the biodiesel’s ester content, the face-centered central composite design (FCCD), integrated with the response surface methodology (RSM), was employed to assess the effect of the following aspects on the process: reaction temperature, MeOH:oil molar ratio, catalyst dosage and reaction time. The regression model presented R2 = 0.9394 and experimentally reached a maximum ester content of 95.9% (relative error < 5%) attributed to the biodiesel attained under the following optimal reaction conditions: temperature of 95 °C, MeOH:oil molar ratio of 13:1, catalyst dosage of 8% and time of 60 min. The NaAlO2/CuFe2O4 catalyst presented a stable catalytic performance during four transesterification cycles (>90.0%) and an efficient magnetic property for the catalyst separation and recovery process (Ms = 23.62 emu g-1). The results showed that the biodiesel’s physicochemical properties were in compliance with ASTM D6751 standard. Finally, this extensive study reveals the basic magnetic heterogeneous catalyst NaAlO2/CuFe2O4 as a practical and promising alternative to produce a sustainable biofuel.
Acesso aberto (Open Access)
Técnicas voltamétricas com eletrodo de filme de bismuto modificado com edta e ebt para determinação de Ca2+ e Mg2+ em biodiesel
(Universidade Federal do Pará, 2016-08-19) MULLER, Renata Medeiros Lobo; MARQUES, Aldalea Lopes Brandes; http://lattes.cnpq.br/0121030502015990; MÜLLER, Regina Celi Sarkis; http://lattes.cnpq.br/654941494386147
This study presents the development of alternative electrochemical methods for the determination of Mg2+ and Ca2+ through voltammetry technique of adsorptive stripping voltammetry (VAdR) with anodic scan. Bismuth film electrode modified with eriochrome black-T (EBT) was used for modification of the electrode in the determination of Mg2+ in the pulse differential mode (DPAdSV), while EDTA has been used for determination of Ca2+ in wave mode square (SWAdSV). The determination of Mg2+ was performed using acetate buffer (0.1 mol L-1) at pH = 4.5, EBT as supporting electrolyte and 1.0 x 10-3 mol L-1 as a binder. Successive additions of aliquots of the stock solution were made Mg2+ 1.0 x 10-3 mol L-1 so that the ion was pre-concentrated on the sensor surface under the following conditions optimized voltammetric: deposition potential (EDEP) = - 1.0 V; Pre time - concentration (Tpre) = 120 s; scan speed (v) = 0.050 V s-1; pulse amplitude (Amp) = 0.1 V. The complex formed Mg2+ EBT showed a peak current of about - 0.6 V. The determination of Ca2+ was made using ammonium buffer (0.01 mol L-1) at pH 9.4, as supporting electrolyte and EDTA 1.0 x 10-2 mol L-1 as a binder under the following optimum conditions: deposition potential (EDEP) = -1.0 V; preconcentration time (Tpre) = 90 sec; frequency (freq.) = 15 Hz; width = 0,075V and Step E) = 0.004 V. The complex formed Ca2+ EDTA showed a peak current of approximately - 0.2 V. The result was consistent statistically considering t -test for a 95% confidence level. The levels were lower CV of 11.0% (Mg2+ and Ca2+), recoveries were in the range 95.0 to 108.0% (Mg2+) and from 97.8 to 105.0% (Ca2+) and the values of detection limits were 1.05 x 10-6 mol L-1 (Mg2+) and 2.8 x 10-7 mol L-1 (Ca2+), and quantitation 3.51 x 10-6 mol L-1 (Mg2+) and 9.46 x 10-7 mol L-1 (Ca2+) for the samples analyzed, showing good accuracy and sensitivity of the proposed method. The values obtained for the samples ranged from 1.47 x 10-5 ± 1.28 x 10-6 mol L-1 (Mg2+) and 5.57 x 10-6 ± 3.77 x 10-7 mol L-1 (Ca2+) on samples of biodiesel. The determination of metals such as Ca2+ and Mg2+ by electrochemical techniques with chemically modified electrodes has as main advantages its detectability and the selectivity.

Navegar

Navegando Programa de Pós-Graduação em Química - PPGQ/ICEN por Agência de fomento "CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior"