https://repositorio.ufu.br/handle/123456789/5136 Fri, 02 Oct 2026 10:29:41 GMT 2026-10-02T10:29:41Z https://repositorio.ufu.br/handle/123456789/50269 Title: Estudo químico e biológico de Microlicia parviflora (Melastomataceae): sazonalidade dos óleos essenciais, metabolômica comparativa e isolamento de metabólitos Abstract: Microlicia parviflora (Melastomataceae) is a poorly studied species, but plants of the genus have been reported to exhibit promising biological activities. Therefore, in the present study, the chemical composition and biological potential were evaluated through three distinct approaches. Initially, the essential oils from leaves collected throughout one year were investigated for their antimicrobial potential, and their chemical compositions were determined by mass spectrometry. The oils exhibited promising antibacterial activity against different oral pathogens, with the most notable inhibitory results obtained against Porphyromonas gingivalis and Actinomyces naeslundii, with minimum inhibitory concentration (MIC) values of 0.39 µg mL–1. Through multivariate statistical analyses, it was possible to group the oils obtained at different times of the year, relating their chemical composition to the rainy and dry seasons; the chemical profile and biological potential of the essential oils from the flowers were also evaluated, which showed a slightly different composition from that of the leaves and were active against the same bacteria. In a second approach, extracts were obtained by maceration of the leaves, flowers, and branches using hexane and ethanol. These extracts were tested against the same bacteria, Candida species, and the protozoa Trypanosoma cruzi and Leishmania infantum. The hexane extracts were active against six of the bacteria tested, with MIC values ranging from 12.5 to 100 µg mL–1, and against L. infantum, with an effective concentration (EC50) ranging from 0.9 to 3.8 µg mL–1. The ethanolic extracts from the three organs and the more polar partitions of the leaves and branches were active against Candida species, including the multidrug-resistant species C. auris, with MIC values of 2.93 µg mL–1. Finally, a comparative study of the chemical composition of leaves, flowers, branches, and roots was performed using metabolomic techniques. With the aid of mass spectrometry and statistical analyses, it was possible to differentiate the organs, showing that the chemical composition of the branches and roots is similar, whereas that of the leaves and flowers is more distinct. These results were also observed by nuclear magnetic resonance spectroscopy. The methanolic extracts of the four organs were tested against phytopathogens associated with different cultivars and against human colorectal and prostate cancer cells. The extracts were active in both assays, showing 100% inhibition of the pathogen Phytophthora infestans and against both types of cancer cells tested. In addition, the study led to the isolation of two compounds obtained from different organs: quercitrin obtained from the ethyl acetate partition of the leaves and tricoumaroyl-spermidine obtained from the ethyl acetate partition of the flowers. Both were reported for the first time in the species, and the spermidine derivative was reported for the first time in the genus. This was the first study conducted on other organs of the species, as well as the first study to investigate the biological activities tested. Thu, 09 Jul 2026 00:00:00 GMT https://repositorio.ufu.br/handle/123456789/50269 2026-07-09T00:00:00Z https://repositorio.ufu.br/handle/123456789/49580 Title: Desenvolvimento de monolitos compósitos hierarquicamente porosos de acetato de celulose funcionalizados com TiO₂ para remoção de corantes em soluções aquosas por adsorção e fotocatálise Abstract: The contamination of aquatic systems by organic dyes constitutes an important environmental problem due to the high chemical stability and low biodegradability of these compounds. In this work, hierarchically porous cellulose acetate monoliths (CAM), both pure and functionalized with TiO₂, were developed aiming at the removal of methylene blue and Rhodamine B dyes through combined adsorption and photocatalysis processes. The materials were obtained by non-solvent-induced phase separation, using DMF and 1-octanol, with the incorporation of different TiO₂ contents. The characterizations confirmed the formation of porous monolithic structures and the incorporation of the inorganic phase into the polymeric matrix. The presence of TiO₂ promoted morphological changes and a significant increase in the specific surface area, with the composites containing 2% and 11% TiO₂ standing out, presenting areas of 54.61 and 57.82 m² g⁻¹, respectively, compared to 23.17 m² g⁻¹ for the pure monolith. In the methylene blue adsorption assays, the materials showed a removal capacity influenced by the composition and porous structure of the monoliths. The kinetic data showed the best fit to the pseudo-second-order model, indicating that the adsorption process is mainly associated with interactions between the dye and the active sites present in the matrix, with contributions from surface area, porosity, and TiO₂ incorporation. In the cyclic adsorption/photocatalysis assays with methylene blue and Rhodamine B, the TiO₂-containing composites showed greater stability in removal capacity over four cycles, evidencing the contribution of photocatalysis to the partial regeneration of the adsorbent sites. Despite the observed diffusional limitations and structural heterogeneity, the results demonstrate that TiO₂-functionalized monoliths have potential for application in wastewater treatment processes, combining a renewable polymeric support, a hierarchically porous structure, and integrated photocatalytic activity. Thu, 14 May 2026 00:00:00 GMT https://repositorio.ufu.br/handle/123456789/49580 2026-05-14T00:00:00Z https://repositorio.ufu.br/handle/123456789/49392 Title: Determinação de amônia volatilizada de solos fertilizados com fotômetro uv-vis portátil e de baixo custo Abstract: The continuous growth of the world population has increased the demand for more efficient food production systems. In Brazil, the agricultural sector faces significant challenges in meeting both domestic and international markets, especially due to the limitation of available land for cultivation. In this context, the use of nitrogen fertilizers stands out as a widely adopted strategy to increase productivity, as it provides essential nutrients for plant development. Among these inputs, urea (CH₄N₂O) is one of the main sources of nitrogen used in agriculture. After its application to the soil, urea is rapidly hydrolyzed by the action of the enzyme urease, resulting in the formation of gaseous ammonia and bicarbonate. This process reduces fertilizer efficiency, increases production costs, and may cause negative environmental impacts, mainly due to ammonia volatilization. Given this scenario, the present work proposes the development of a portable analytical method capable of quantifying volatilized ammonia in fertilized soils through active sampling and measurements carried out directly in the field. The experimental procedure consisted of collecting air containing NH₃ by bubbling it through a sulfuric acid solution with methyl orange, using a flow rate of 50 mL·min⁻¹. Absorbance readings were performed using a portable photometer produced by 3D printing, equipped with a 490 nm wavelength LED, a digital optical sensor, and an air pump, all integrated into an Arduino microcontroller. The method showed linear behavior in the range of 0 to 3.0 × 10⁻⁶ mol of NH₃, considering a collection time of 20 minutes. In addition, its application allowed the quantification of volatilized ammonia over four days, with collections carried out every 24 hours after fertilizer incorporation into the soil. As a form of validation of the sampling procedure, a parallel test was conducted in the Technical Assistance laboratory of Adfert. In this test, the quantification of ammonia resulting from urea volatilization in the soil was performed by titration of the solution obtained from filter papers used to capture the analyte. Fri, 31 Jul 2026 00:00:00 GMT https://repositorio.ufu.br/handle/123456789/49392 2026-07-31T00:00:00Z https://repositorio.ufu.br/handle/123456789/49375 Title: Desenvolvimento de um método eletroanalítico para a determinação de sibutramina em amostras biológicas e forenses utilizando folha de grafite como eletrodo de trabalho Abstract: The detection of sibutramine in different matrices is of significant importance due to its irregular use in dietary supplements and illicit weight-loss products, posing risks to public health and implications for forensic and antidoping analyses. In this context, electrochemical methods stand out as attractive alternatives to conventional techniques, offering low cost, rapid analysis, high sensitivity, and potential for in situ applications. This study aimed to develop an electroanalytical method for the determination of sibutramine (SIB) using a graphite sheet as the working electrode. Different surface modification strategies were evaluated, and electrochemical treatment was selected due to its superior analytical performance. The treated electrode was characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), demonstrating an increase in electroactive area and improved charge transfer kinetics. The electrochemical behavior of SIB was investigated, indicating a predominantly adsorption-controlled oxidation process. Differential pulse voltammetry (DPV) and square wave voltammetry (SWV) were evaluated, with SWV selected due to its higher analytical sensitivity. After optimization, two linear response ranges were obtained: 0.1–5.0 μmol L⁻¹ (R² = 0.993) and 7.5–45.0 μmol L⁻¹ (R² = 0.994). The limits of detection (LOD) were 0.01 μmol L⁻¹ for the first range and 1.89 μmol L⁻¹ for the second, while the limits of quantification (LOQ) were 0.03 μmol L⁻¹ and 6.32 μmol L⁻¹, respectively. The developed method was successfully applied to the determination of SIB in synthetic urine, multivitamin samples, and seized materials, showing satisfactory recovery results. Validation was performed through comparison with an HPLC-UV/Vis reference method, demonstrating good agreement between the results. The findings indicate that the electrochemically treated graphite sheet electrode is a promising, low-cost, and easy-to-prepare alternative for the determination of SIB in different matrices, with potential applications in forensic analysis, sanitary control, and antidoping. Tue, 19 May 2026 00:00:00 GMT https://repositorio.ufu.br/handle/123456789/49375 2026-05-19T00:00:00Z