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Prospecção química e avaliação do potencial antimicrobiano e antidiabético de espécies dos gêneros Cassia e Senna (Fabaceae) por CLUE-ESI-EM/EM

2026-07-07T06:27:35Z

Title: Prospecção química e avaliação do potencial antimicrobiano e antidiabético de espécies dos gêneros Cassia e Senna (Fabaceae) por CLUE-ESI-EM/EM Abstract: The Cerrado and the Atlantic Forest are Brazilian biomes rich in biodiversity, harboring a variety of medicinal plant species. Among them, species of Cassia and Senna have stood out for their medicinal properties and have aroused scientific interest due to the presence of special metabolites with biological potential. In this study, six species of these genera were collected (C. fistula, C. grandis, C. javanica, S. multijuga, S. rugosa, and S. velutina), and nine leaf and flower extracts were prepared and subjected to liquid-liquid extraction to obtain the organic fractions. The obtained extracts were analyzed by UPLC- IES-MS/MS, in negative and positive modes. In this process, flavonoids, an anthraquinone, and proanthocyanidins, along with other classes of compounds, were identified. In the antibacterial activity assay, using cariogenic bacteria, the EE demonstrated moderate activity, with minimum inhibitory concentration (MIC) values ranging from 100 to 400 μg mL–1, the exception being the EE from S. velutina leaves, which exhibited an MIC of 25 μg mL–1 for Streptococcus mitis and 50 μg mL–1 for Porphyromonas gingivalis. In the assay using anaerobic bacteria, the ethyl acetate fraction of S. velutina flowers exhibited a MIC of 50 μg mL–1 against S. mitis. In the assay using aerobic bacteria, the hexane fractions of S. rugosa (flowers) and C. javanica (leaves and flowers) showed antibacterial activity with MIC values ranging from 6.25 to 25 μg mL–1 against P. gingivalis and Actinomyces naeslundii. In the assay to evaluate antifungal activity using yeasts of the genus Candida, the most promising EE were those of S. rugosa and C. javanica flowers, as well as S. velutina leaves and flowers, exhibiting MIC values between 5.86 and 11.72 μg mL–1 against C. glabrata. The most polar fractions of S. rugosa leaves and flowers and C. javanica flowers showed MICs between 2.93 and 23.4 μg mL–1 against C. albicans and C. glabrata. A very promising result was obtained from the ethyl acetate fraction of S. velutina flowers, exhibiting an MIC of 1.46 μg mL–1 against C. glabrata. This fraction was selected for chemical study based on analysis by UPLC-ESI-MS/MS, which revealed the presence of proanthocyanidins, from which the compounds (ent)-cassiaflavan-gallocatechin (A), (ent)-cassiaflavan-(ent)-cassiaflavan- catechin (D), and a mixture of (ent)-cassiaflavan-(4→8)-(epi)-catechin B and C were isolated. The anti-Candida potential of these compounds was evaluated against strains of C. albicans, C. glabrata, and C. tropicalis, and they showed selectivity against C. glabrata with MICs between 1.95 and 15.69 μg mL–1. C. javanica, a species used in folk medicine for the treatment of diabetes, was selected for chemical and antidiabetic study. The dichloromethane fraction of C. javanica flowers was one of the most active in the enzymatic assay against α-amylase and α-glucosidase, and in anti-glycation assays. Chemical analysis of this fraction isolated kaempferol (E), rhein (F), elegentin (G), and afzelin (H), which were also subjected to α-glucosidase and anti-glycation assays. Compound E was one of the most active, particularly in inhibiting α-amylase with an IC50 of 0.04 ± 0.003 μg mL⁻¹ (positive control triticum, 0.2 ± 0.00 μg mL⁻¹). The results of the biological assays highlight the relevance of chemical and pharmacological investigation of Cassia and Senna species, which are still underexplored when it comes to investigating natural products with antimicrobial and antidiabetic potential.

Influência da co-dopagem com íons La3+ em sistemas binários de óxidos de SiO2-TiO2:Eu3+ obtidos pelo método sol-gel

2026-05-23T06:23:34Z

Title: Influência da co-dopagem com íons La3+ em sistemas binários de óxidos de SiO2-TiO2:Eu3+ obtidos pelo método sol-gel Abstract: This study investigates the synthesis and characterization of photoluminescent materials based on SiO2-TiO2 matrices co-doped with Eu3+ and La3+. Prepared via the sol-gel method and calcined at 750 °C, the matrices were analyzed by X-ray Diffraction (XRD), Raman spectroscopy, Fourier-Transform Infrared spectroscopy (FTIR), Diffuse Reflectance Spectroscopy (DRS), Scanning Electron Microscopy (SEM), and Photoluminescence (PL). Structural results confirmed the stabilization of the anatase phase, where the incorporation of La3+ acted as a crystal growth inhibitor, except at concentrations of 0.3 and 1.0 mol%, which exhibited a singular bulk-like behavior regime. Diffuse reflectance analysis (DRS) revealed an adjustable direct band gap between 2.75 and 3.02 eV, correlated with the structural disorder monitored by the Urbach energy. Thermal treatment proved crucial, promoting the removal of hydroxyl suppressors and resulting in an average 6.5-fold (547%) jump in luminescence lifetimes (τ), which reached values exceeding 1000 µs. Spectroscopic analysis indicated that La3+ co-doping induces a symmetry breaking at the Eu3+ local site (site symmetries Cs, Cn ou Cnv), evidenced by the splitting of the 5D0→7F1 transition into three singlets and a 120% increase in the emission intensity of the 5D0→7F2 hypersensitive band. In situ PL monitoring as a function of temperature confirmed the reversibility and thermal robustness of the system, mitigating quenching effects. These findings demonstrate the high potential of SiO2-TiO2:Eu3+,La3+ composites for the development of advanced photonic devices, such as WLEDs and high-sensitivity sensors for optical thermometry.

Development of conductive and printable filaments for electrochemical sensors applied to environmental, pharmaceutical, food and biological analyses

2026-05-13T06:23:55Z

Title: Development of conductive and printable filaments for electrochemical sensors applied to environmental, pharmaceutical, food and biological analyses Abstract: Chemical sensors have been widely developed in response to the growing demand for the monitoring of analytes in environmental, biological, forensic and food samples. Among them, electrochemical sensors stand out for translating chemical information into measurable electrical signals and for offering advantages such as good selectivity, sensitivity, low limit of detection, ease of miniaturisation and versatility for both materials and designs. In this context, these devices have grown together with advances in new manufacturing technologies, especially additive manufacturing, which has emerged as a promising approach for the production of electrochemical sensors. In parallel, new conductive filaments have been developed to improve electrochemical responses, expand possibilities for new applications and incorporate sustainability perspective. However, as this is still a relatively recent field, challenges remain in regard to the achievement of improved electrochemical responses, better printability and the use of new polymers to broaden applications. Thus, this Thesis aimed to explore the fabrication and application of new alternative filaments produced in the laboratory for the monitoring of paracetamol, ascorbic acid, dopamine, uric acid, nitrite and carbendazim, demonstrating the versatility of these devices in environmental, biological and food samples. Divided into six chapters, the work presents: general introduction, filaments modified with carbon nanodiamonds and functionalised nanodiamonds, demonstrating the possibility of modifying and improving electrochemical responses; filaments with the addition of edible oils as plasticisers, with a focus on sustainability and demonstrating, for the first time, the influence of specific plasticisers on sensor responses; alternative thermoplastic polyurethane (TPU)-based filaments, used both as sensors obtained from the direct use of the filament itself and as printed electrodes which, compared with polylactic acid (PLA), show greater flexibility without loss of analytical performance, in addition to biocompatibility, thereby expanding the potential for application in wearable sensors; and, finally, more sustainable filaments produced from high-density polyethylene recycled (rHDPE) from cleaning-product packaging, with emphasis on greater chemical resistance and durability when compared with other polymers. All materials were extensively characterised, and the electroanalytical devices were evaluated against the proposed applications. The results expand the possibilities for the development and optimisation of electrochemical sensors, highlighting efficient, versatile, low-cost materials with low waste generation.

Determinação do teor de biodiesel metílico de palmiste (BMPALM) e pinhão manso (BMPM) usando espectroscopia no infravermelho médio e calibração multivariada por resolução multivariada de curvas com mínimos quadrados alternados (MCR-ALS) e regressão por vetor de suporte (SVR)

2026-02-06T06:27:00Z

Title: Determinação do teor de biodiesel metílico de palmiste (BMPALM) e pinhão manso (BMPM) usando espectroscopia no infravermelho médio e calibração multivariada por resolução multivariada de curvas com mínimos quadrados alternados (MCR-ALS) e regressão por vetor de suporte (SVR) Abstract: The growing demand for biodiesel has increased the risk of marketing fuels that do not meet the standards established by the Brazilian National Agency of Petroleum, Natural Gas and Biofuels (ANP), with the concentration of biodiesel in diesel blends being one of the main parameters of non-compliance. In response to this analytical demand, this study developed methods for quantifying the content of palm kernel methyl biodiesel (BMPALM) and jatropha methyl biodiesel (BMPM) in diesel blends, using mid-infrared (MIR) spectroscopy combined with multivariate calibration techniques: multivariate curve resolution with alternating least squares (MCR-ALS), support vector regression (SVR), and partial least squares (PLS) as the reference method. Samples were prepared in different concentrations (1.00 to 30.00% v/v), submitted to spectral acquisition, and then modeled using chemometric approaches. The models built for each type of biodiesel showed good accuracy, with low root mean square errors (RMSEs < 1%) in all stages (calibration, cross-validation, and prediction), and good linearity, as evidenced by determination coefficients (R²) very close to 1. Statistical tests (F-test) indicated similar variances between most models, with few exceptions in specific comparisons between techniques. The results confirm that the combination of FT-MIR spectroscopy with advanced multivariate calibration methods, especially SVR and MCR-ALS, enables reliable quantification of BMPALM and BMPM in diesel blends. Moreover, these two methods offer advantages over PLS, such as lower sample requirements for model construction and reduced operational costs, representing promising alternatives for quality control in the fuel industry and for regulatory monitoring.