PPGQ https://repositorio.ufpb.br/jspui/handle/tede/7029 2026-07-19T06:14:27Z 2026-07-19T06:14:27Z Arruda, Joaldo Garcia https://repositorio.ufpb.br/jspui/handle/123456789/38350 2026-07-17T06:11:26Z 2024-04-29T00:00:00Z

Título: Propriedades estruturais e luminescentes de novos compostos carboxilatos e β-dicetonatos de íons lantanídeos Autor(es): Arruda, Joaldo Garcia Orientador: Teotonio, Ercules Epaminondas de Sousa Abstract: In this research, two independent studies were conducted to investigate new lanthanide ion based compounds using carboxylate and β-diketonate ligands as luminescence sensitizers. In the first class, two different types of systems were explored: N-phthaloylglycine (phtgly) with N-(2-carboxybenzoyl) glycine (cbgly) or terephthalic acid (1,4-bdc), resulting in the formation of coordination polymers (CPs) with general formulas: {{[Ln2(phthgly)6(H2O)2]⋅(H2O)2}, {[Ln(phthgly)(cbgly)(H2O)2].(H2O)}, and {[Ln2(phthgly)4(bdc)(H2O)6](H2O)4}∞, as well as doped systems {[EuxTb1-x(phthgly)(cbgly)(H2O)2].(H2O)} (x= 0.25, 0.50, 0.75). On the other hand, the class of β-diketonate was used with auxiliary ligands, resulting in the formation of coordination compounds with general formulas [Ln(dbm)2(NO3)(L)2] and [Ln(dpm)(NO3)2(tchpo)2], where Ln: Eu3+, Tb3+, and Gd3+ and β-diketonate is represented by dbm: 2-diphenylmethane, dpm: dipivaloylmethane. The auxiliary ligands L include: tchpo (tricyclohexylphosphine oxide), topo (trioctylphosphine oxide), and tpAsO (triphenylarsine oxide). The synthesized systems were characterized using elemental microanalysis of C, H, and N, infrared absorption spectroscopy (FT-IR), diffuse reflectance, thermogravimetric analysis and nuclear magnetic resonance spectroscopy (NMR). Furthermore, the complexes {[Ln2(phthgly)6(H2O)2]⋅(H2O)2}, {[Ln2(phthgly)4(bdc)(H2O)6](H2O)4}∞, [Ln(dbm)2(NO3)(L)2] and [Ln(dpm)(NO3)2(tchpo)2] were obtained as single crystals, allowing their structures resolution by the single-crystal X-ray diffraction method. The luminescent properties were experimentally investigated based on spectral data of excitation, emission, and lifetime decay curves of the 5D0 emitting state and intrinsic quantum yield (𝑄𝐿𝑛𝐿𝑛). The spectra of the system {[Eu2(phthgly)4(bdc)(H2O)6](H2O)4}∞ showed that the intramolecular energy transfer processes are minimally operative, circumvented by the doping process with Tb3+ ions. Meanwhile, in the [Eu(dpm)(NO3)2(tchpo)2] system, very low luminescence intensity was observed due to an efficient luminescent quenching process via ligand-to-metal charge transfer (LMCT). Additionally, theoretical studies based on the Time-Dependent Density Functional Theory (TD-DFT) calculations, using the CAM-B3LYP functional and DKH2 relativistic Hamiltonian, together with results obtained from calculations using the JOYSpectra platform corroborated the experimental results. Based on these findings, new heteronuclear compounds of lanthanide ions with different carboxylate and β-diketonate ligands present potential for various applications. Editor: Universidade Federal da Paraíba Tipo: Tese

2024-04-29T00:00:00Z Nobrega, Martha Maria Gomes https://repositorio.ufpb.br/jspui/handle/123456789/38247 2026-06-28T06:16:13Z 2025-12-15T00:00:00Z

Título: Estudo do armazenamento, das isotermas de adsorção e aplicação cosmética dos pós de Saccharomyces cerevisiae obtidos por secagem em camada de espuma Autor(es): Nobrega, Martha Maria Gomes Orientador: Cavalcante, Josilene de Assis Abstract: The valorization of agro-industrial by-products represents a fundamental strategy for the development of more sustainable and economically viable production processes. The residual biomass of Saccharomyces cerevisiae, obtained after successive fermentation cycles in cachaça production, exhibits a composition rich in proteins, polysaccharides and minerals, features that make it a material with high biotechnological potential, despite still being commonly discarded by the industry. This study aimed to evaluate the technical feasibility, stability, and cosmetic potential of the powder obtained by foam-mat drying. Moisture adsorption isotherms were determined at 15, 30 and 45 °C, with the Henderson model providing the best fit to the experimental data, yielding type II sigmoidal curves. Thermodynamic analysis revealed that the isosteric heat of sorption (Qst) ranged from 44 to 50 kJ mol−1, indicating strong initial interactions between water molecules and active sites of the matrix. Differential variations in enthalpy (ΔH) and entropy (ΔS) decreased with increasing moisture content, evidencing greater organization of the adsorbed water layers and lower energy required for sorption. Negative Gibbs free energy (ΔG) values confirmed the spontaneity of the process and the affinity of the dried yeast for water. Among the drying conditions evaluated, the central point (60 °C and 10% foaming agent) showed the best performance, resulting in a more stable and less hygroscopic powder, which was selected for the subsequent stages of the study. During 90 days of storage in different packaging materials, under ambient (26 °C/75% RH) and accelerated (40 °C/75% RH) conditions, storage time was the most influential factor, followed by temperature and packaging type. Increased time and temperature intensified moisture gain and color variations, while high-density polyethylene (HDPE) packaging provided the best water-vapor barrier, preserving physicochemical properties for longer periods. Shelf life was estimated using kinetic modeling based on the Arrhenius equation, considering water activity and moisture content as critical parameters. The material packaged in HDPE and stored under ambient conditions showed the longest stability, with a shelf life of 12 months. In addition, the powder obtained under the central-point condition was incorporated into a cosmetic facial cream formulation, which exhibited a homogeneous appearance and no phase separation. Rheological analysis indicated pseudoplastic behavior well described by the Herschel–Bulkley model, demonstrating good structural stability. The presence of the active ingredient acted as a rheological modulator, reducing rigidity and improving flow, which resulted in greater spreadability and superior sensory performance compared with the control formulation. These results confirm that foam-mat drying is a viable and efficient technique for producing Saccharomyces cerevisiae powders with adequate stability and strong potential for application in sustainable cosmetic products. Editor: Universidade Federal da Paraíba Tipo: Dissertação

2025-12-15T00:00:00Z Abrantes, Paloma Gomes de https://repositorio.ufpb.br/jspui/handle/123456789/38242 2026-06-27T06:13:13Z 2025-10-22T00:00:00Z

Título: Síntese de compostos bioativos via condensação de Knoevenagel e reações sequenciais utilizando quitosana como organocatalisador reciclável Autor(es): Abrantes, Paloma Gomes de Orientador: Vale, Juliana Alves Abstract: The Knoevenagel condensation reaction is a widely explored variant of aldol reactions, used to enhance the functionality of carbon chains in the search for new bioactive molecules. As it is a catalyst dependent process, the pursuit of innovative catalytic methodologies capable of promoting faster, more selective, and more efficient reactions has intensified. In this context, low molecular weight commercial chitosan (LWC) and EDTA-modified chitosan (LWC- EDTA-72h) were applied in the synthesis of 3-coumarin-carboxylic acids, Knoevenagel adducts derived from aromatic aldehydes or isatin, as well as xanthene and tetraketone derivatives. The obtained compounds were characterized by 1H and 13C NMR, melting point analysis, and evaluated for antileishmanial, antimicrobial, antitumor in vitro, and larvicidal activity against Aedes aegypti. LWC-EDTA-72h acted as a bifunctional heterogeneous organocatalyst at room temperature in reactions between aldehydes or isatins and malononitrile in ethanol:water (3:7, v/v), producing the desired adducts (1a–l and 2a–h) in 0.5–120 min with yields of 83–96%. The catalyst maintained its activity over six recovery and reuse cycles. In larvicidal assays, the Knoevenagel adducts 1c (R = 4-NO2) and 1g (R = 3-OCH3) exhibited LC50 values of 3.39 and 5.13 ppm, respectively, altering larval hemolymph without significant increases in nitric oxide (NO). As antimicrobials, 1a (R = H), 1f (R = 3-NO2), and 1h (R = 2- NO2) inhibited all evaluated strains (MIC = 512–1024 μg/mL). Against Leishmania infantum, the isatin-derived Knoevenagel adducts 2b (R = 5-Cl; R' = H), 2c (R = 5-Br; R' = H), and 2g (R = 5-CH3; R' = N-benzyl) showed IC50 values of 15.05, 18.38, and 12.7 μM (promastigote) and EC50 values of 5.74, 4.64, and 3.8 μM (axenic amastigote), with no cytotoxicity toward human erythrocytes. In PBMCs, they exhibited CC50 values of 25.2–34.41 μM, with SI values of 4.39– 7.42. No isatin-derived Knoevenagel adduct showed antimicrobial activity at the tested concentrations (2–1024 μg/mL). In the sequential synthesis of 3-coumarinocarboxylic acid 3a (R = H), commercial LWC was the most efficient catalyst in water or ethanol:water (3:7, v/v) at 75 °C, providing the product in short reaction times and good yields. With substituted salicylaldehydes, new coumarin derivatives (3b–i) were obtained in 10–45 min with yields of 77–88%, and up to four catalyst reuse cycles. Acids 3c–e, 3h, and 3i inhibited microbial growth from 1024 μg/mL, with compound 3d (R = 5-Br) being considered bactericidal and fungicidal. Xanthene (4a–g) and tetraketone (5a–g) derivatives were obtained through sequential reactions of aromatic aldehydes and dimedone (1:2 equivalents) in water at 75 °C using commercial LWC. The processes proved simple, sustainable, and efficient. Xanthene derivatives were obtained in 10–60 min (73–93%) and tetraketone in 10–20 min (82–94%), maintaining their structure and catalytic activity after six recycling cycles. In the biological assays, xanthene derivatives showed greater cytotoxicity than tetraketone. Compound 4f (R = 4-OH) was the most active (>94% inhibition) against chronic myeloid leukemia (K-562), human colon cancer (HCT-116), and lung carcinoma (A-549) cell lines, with IC50 values of 12.08, 6.61, and 5.54 μM, respectively, but exhibited high cytotoxicity toward non-tumor cells (MRC-5, 96.07%), resulting in a low SI. Nevertheless, it stands out as a lead compound for future modifications aiming at improved selectivity. Editor: Universidade Federal da Paraíba Tipo: Tese

2025-10-22T00:00:00Z Gomes, Glaucio Jefferson Araújo https://repositorio.ufpb.br/jspui/handle/123456789/38236 2026-06-27T06:13:10Z 2024-11-13T00:00:00Z

Título: Desenvolvimento de testes para detecção da COVID-19 empregando análise multivariada em associação com espectrofluorimetria ou NIR portátil Autor(es): Gomes, Glaucio Jefferson Araújo Orientador: Lemos, Sherlan Guimarães Abstract: The outbreak of Coronavirus Disease (COVID-19) triggered a global health emergency, resulting in millions of deaths. During this period, efforts to control the spread of the virus and resume activities were significantly impacted by the availability of supplies and skilled labor necessary for accurately diagnosing the population. The challenges faced by many countries in conducting mass diagnostics through techniques such as RT-PCR highlight the ongoing need to seek alternative testing strategies that are effective, less reliant on high-cost raw materials, and scalable for widespread application. In this study, we explore the use of spectroscopic analysis of blood serum samples combined with multivariate analysis techniques for COVID-19 diagnosis. Two approaches were tested: the first using molecular fluorescence spectroscopy, and the second employing near- infrared spectroscopy with a portable device. In each approach, spectra from samples of patients with positive and negative COVID-19 diagnoses were obtained and used to train and validate classification models based on SIMCA, DD-SIMCA, PCA-DA, and PLS-DA modeling techniques. Among the tested approaches, analyses with excitation at 280 nm allowed the development of a PCA-DA classification model with a sensitivity of 0.98, selectivity of 0.84, and efficiency of 95%. This model demonstrated high efficiency in detecting seropositive samples, with only minor difficulty in classifying seronegative samples. In the analyses using excitation-emission matrix spectra, the DD-SIMCA model generated through PARAFAC decomposition best met the desired objectives, achieving an overall efficiency of 96%, sensitivity of 0.98, and selectivity of 0.92. Finally, a new method is presented for classifying blood serum samples as positive or negative for COVID-19 infection, using fluorescence spectroscopy analysis combined with multivariate analysis techniques. The use of spectroscopy in the analysis of serum samples proved to be effective in generating discrimination models that can be used to analyze new samples and determine whether the recorded signal is characteristic of a patient infected with SARS-CoV-2. The findings of this study proved to be promising and may contribute to the development of auxiliary diagnostic methods that are cost-effective, easy to perform, and provide rapid and reliable results. Editor: Universidade Federal da Paraíba Tipo: Tese

2024-11-13T00:00:00Z