Maria Joao dos Reis Matos Cebola
@egasmoniz.com.pt
Instituto Universitário Egas Moniz
Egas Moniz School of Health & Science
Scopus Publications
Scopus Publications
Ana L. Santos, Maria João Cebola, Jorge Antunes, and Diogo M. F. Santos
MDPI AG
Green hydrogen production seems to be the best route to achieve a sustainable alternative to fossil fuels, as hydrogen has the highest energy density on a mass basis and its combustion does not produce greenhouse gases. Water electrolysis is the method of choice for producing green hydrogen. Among commercially available water electrolysis systems, alkaline water electrolysis (AWE) is the most well-established technology, which, nevertheless, still needs to improve its efficiency. Since the electrodes’ performance is of utmost importance for electrolysis efficiency, nickel foam (NF) and stainless steel foam (SSF) electrodes were analyzed via voltammetry to validate their catalytic activity toward the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in 30 wt.% NaOH electrolyte solution. Moreover, at a current density of 50 mA cm−2, the NF and the SSF exhibited good stability, with the potential for HER and OER stabilizing at −0.5 V and 1.6 V vs. reversible hydrogen electrode. A lab-scale electrolyzer attained current densities of 10, 20, and 50 mA cm−2 at small cell voltages of 1.70 V, 1.80 V, and 1.95 V. The results validated NF and SSF as electrodes for a high-performance AWE electrolyzer, especially at higher temperatures. They ensured the progress for the project’s next stage, i.e., constructing an electrolyzer at a pilot scale.
Paula Pereira, Elisabete Muchagato Mauricio, Maria Paula Duarte, Katelene Lima, Ana S. Fernandes, Gabriela Bernardo-Gil, and Maria-João Cebola
Elsevier BV
Ana L. Santos, Maria-João Cebola, and Diogo M. F. Santos
MDPI AG
Environmental issues make the quest for better and cleaner energy sources a priority. Worldwide, researchers and companies are continuously working on this matter, taking one of two approaches: either finding new energy sources or improving the efficiency of existing ones. Hydrogen is a well-known energy carrier due to its high energy content, but a somewhat elusive one for being a gas with low molecular weight. This review examines the current electrolysis processes for obtaining hydrogen, with an emphasis on alkaline water electrolysis. This process is far from being new, but research shows that there is still plenty of room for improvement. The efficiency of an electrolyzer mainly relates to the overpotential and resistances in the cell. This work shows that the path to better electrolyzer efficiency is through the optimization of the cell components and operating conditions. Following a brief introduction to the thermodynamics and kinetics of water electrolysis, the most recent developments on several parameters (e.g., electrocatalysts, electrolyte composition, separator, interelectrode distance) are highlighted.
Ana Henriques Mota, Joana Marçalo Andrade, Epole N Ntungwe, Paula Pereira, Maria João Cebola, Maria Gabriela Bernardo-Gil, Jesús Molpeceres, Patrícia Rijo, Ana Silveira Viana, Lia Ascensão,et al.
Thomas Telford Ltd.
Sambucus nigra L. is a well-known species with a wide range of medicinal properties. In this work, supercritical fluid extracts were obtained from fresh and dried elderberries of S. nigra L.: A (dried berries, ethanol (C2H5OH) absolute), B (dried berries, ethanol 96%), C (dried berries, ethanol 70%) and D (fresh berries, ethanol 96%). Evaluation of the in vitro enzymatic activities and antioxidant activity (AA) of the extracts and a preliminary assessment of their safety were carried out. The most promising extracts were selected for encapsulation in polymeric nanoparticles (NPs). All extracts demonstrated low to moderate AA, and they did not reveal any antimicrobial activity against the bacteria and yeasts tested. No toxic effect in the Artemia salina model was observed. Due to the moderate or good AA, anti-collagenase and anti-elastase activities, A and C extracts were selected and then successfully encapsulated into poly(lactide-co-glycolide) (PLGA) NPs. According to morphological analysis, empty PLGA NPs had a rounded irregular shape and seemed somewhat collapsed, while PLGA NPs loaded with extract A or C exhibited a spherical shape with a smooth surface. The encapsulation process produced a slight increase in the NP size. Further studies will include the optimization of extract conditions in order to improve the yield of extraction, as well as the in vivo evaluation of these nanocarriers.
Epole Ntungwe N, Eva M. Domínguez-Martín, Amilcar Roberto, Joana Tavares, Vera M. S. Isca, Paula Pereira, Maria-João Cebola, and Patrícia Rijo
Bentham Science Publishers Ltd.
Medicinal plants are a good source of novel therapeutic drugs, due to the phytochemicals present. Artemia, commonly known as brine shrimp, is a tiny halophilic invertebrate belonging to class Crustacean, which plays an important role in saline aquatic and marine eco-systems. Besides its usage in aquaculture, it is also highly valued for its application in toxicity detection and it is used in areas such as Ecology, Physiology, Ecotoxicology, Aquaculture and Genetics. Furthermore, Artemia based lethality assay (brine shrimp lethality assay, BSLA) is rapid, convenient and low cost. Presently, brine shrimp lethality assays are enormously employed in research and applied toxicology. It has been used in the study of natural products as a preliminary toxicity assay to screen a large number of extracts and compounds for drug discovery in medicinal plants. The aim of this review paper is to collect, organize, select and discuss the existing knowledge about the different uses of Artemia salina as a bench-top bioassay for the discovery and purification of bioactive natural products.
Catarina Garcia, Epole Ntungwe, Ana Rebelo, Cláudia Bessa, Tijana Stankovic, Jelena Dinic, Ana Díaz-Lanza, Catarina P. Reis, Amílcar Roberto, Paula Pereira,et al.
MDPI AG
The Plectranthus genus is commonly used in traditional medicine due to its potential to treat several illnesses, including bacterial infections and cancer. As such, aiming to screen the antibacterial and cytotoxic activities of extracts, sixteen selected Plectranthus species with medicinal potential were studied. In total, 31 extracts obtained from 16 Plectranthus spp. were tested for their antibacterial and anticancer properties. Well diffusion method was used for preliminary antibacterial screening. The minimum inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) values of the five most active acetonic extracts (P. aliciae, P. japonicus, P. madagascariensis var. “Lynne”, P. stylesii, and P. strigosus) were determined. After preliminary toxicity evaluation on Artemia salina L., their cytotoxic properties were assessed on three human cancer cell lines (HCT116, MCF-7, and H460). These were also selected for mechanism of resistance studies (on NCI-H460/R and DLD1-TxR cells). An identified compound—parvifloron D—was tested in a pair of sensitive and MDR-Multidrug resistance cancer cells (NCI-H460 and NCI-H460/R) and in normal bronchial fibroblasts MRC-5. The chemical composition of the most active extract was studied through high performance liquid chromatography with a diode array detector (HPLC-DAD/UV) and liquid chromatography–mass spectrometry (LC–MS). Overall, P. strigosus acetonic extract showed the strongest antimicrobial and cytotoxic potential that could be explained by the presence of parvifloron D, a highly cytotoxic diterpene. This study provides valuable information on the use of the Plectranthus genus as a source of bioactive compounds, namely P. strigosus with the potential active ingredient the parvifloron D.
Carlos E. S. Bernardes, Catarina Garcia, Filipe Pereira, Joana Mota, P. Pereira, Maria J. Cebola, Catarina P. Reis, Isabel Correia, M. Fátima M. Piedade, Manuel E. Minas da Piedade,et al.
American Chemical Society (ACS)
The abietane 7α-acetoxy-6β-hydroxyroyleanone (AHR), obtained from plant extracts, is an attractive lead for drug development, given its known antimicrobial properties. Two basic requirements to establish any compound as a new drug are the development of a convenient extraction process and the characterization of its structural and thermal properties. In this work seven different methods were tested to optimize the extraction of AHR from Plectranthus grandidentatus. Supercritical fluid extraction (SFE) proved to be the method of choice, delivering an amount of AHR (57.351 μg·mg-1) approximately six times higher than the second best method (maceration in acetone; 9.77 μg·mg-1). Single crystal X-ray diffraction analysis of the ARH molecular and crystal structure carried out at 167 ± 2 K and 296 ± 2 K showed only a single phase, here dubbed form III (orthorhombic space group P21212), at those temperatures. The presence of two other polymorphs above room temperature was, however, evidenced by differential scanning calorimetry (DSC). The three forms are enantiotropically related, with the form III → form II and form II → form I transitions occurring at 333.5 ± 1.6 K and 352.0 ± 1.6 K, respectively. The fact that the transitions are reversible suggests that polymorphism is not likely to be an issue in the development pharmaceutical formulations based on ARH. DSC experiments also showed that the compound decomposes on melting at 500.8 ± 0.8 K. Melting should therefore be avoided if, for example, strategies to improve solubility based on the production of glassy materials or solid dispersions are considered.
Paula Pereira, Maria-João Cebola, M. Conceição Oliveira, and M. Gabriela Bernardo Gil
Springer Science and Business Media LLC
Paula Pereira, Maria-João Cebola, M. Conceição Oliveira, and M. Gabriela Bernardo-Gil
Elsevier BV
Paula Pereira, M. Gabriela Bernardo-Gil, M. João Cebola, Elisabete Mauricio, and Anabela Romano
Elsevier BV
Paula Pereira, Maria-João Cebola, and M. Bernardo-Gil
MDPI AG
The chemical composition of the essential oil of Portuguese myrtle was determined at different developmental stages of the plant: pre-flowering, flowering, unripe and ripe berries. The oil was extracted separately by Clevenger distillation from leaves, branches and berries. The yields vary from 0.33% to 0.74% for leaves, 0.02% to 0.19% for branches, and 0.11% to 0.23% for berries. The highest yields were obtained for the leaves in October, and for the berries in September; branches show similar values in the months of June, July and September, and the samples collected in May and October produced very little amount of oil. Altogether, September seems to be the month with the best yields for the three parts of the plant. The essential oils were analyzed by GC and GC/MS, and a total of thirty five components were identified. The major components were limonene+1,8-cineole [25.9% (berries)–39.5% (leaves)], myrtenyl acetate [6.6% (berries)–24.8% (leaves)], α-pinene [9.7% (berries)–21.5% (leaves)], and linalool [6.2% (leaves)–36.5% (berries)]. Portuguese myrtle belongs to the group of myrtles which are characterized by the presence of myrtenyl acetate as one of the major components.
Rui Ruivo, M. João Cebola, Pedro C. Simões, and M. Nunes da Ponte
American Chemical Society (ACS)
A mixture that partially resembles the distillates obtained from the deodorization process of olive oils was used as a case study to test and develop mass-transfer models valid for supercritical fluid processes. Such models are useful engineering tools that provide a theoretical background for the scale-up of industrial plants. In the first part of this series of papers, the fractionation performance of the model mixture squalene/methyl oleate by supercritical carbon dioxide in a countercurrent packed column containing a corrugated gauze-type structured packing was presented. This second part presents a general correlation for predicting the mass-transfer efficiency of the high-pressure packed column. Several correlations taken from the literature were used and their results compared with the experimentally determined mass-transfer coefficients and holdup. A model formerly developed for distillation columns was found to be valid for our high-pressure system. It was found that the area of the gauze packing...
K Chylinski, M.J Cebola, A Meredith, G Saville, and W.A Wakeham
Elsevier BV
Rui Ruivo, Maria J. Cebola, Pedro C. Simões, and M. Nunes da Ponte
American Chemical Society (ACS)
The design of countercurrent packed columns operating under high-pressure conditions requires knowledge of their hydrodynamic and mass transfer behavior. A laboratory-scale continuous supercritical fluid extraction apparatus was developed with the purpose of obtaining data needed for such designs. The current work is part of a study to assess the feasibility of supercritical carbon dioxide in fractionating a mixture of squalene and methyl oleate. This mixture partly emulates the residues obtained from the olive oil refining process. Phase equilibrium data were previously measured to evaluate the best operating conditions. Here, we examine the continuous fractionation of two different feeds, with 40 and 70 wt % of squalene, under various extraction conditions. An extraction yield as high as 90 wt % of squalene in the raffinate phase was achieved. The selectivity and extraction efficiency were determined as functions of the oil-to-carbon dioxide flow ratio as well as the reflux ratio. In a subsequent paper ...
M.J. Cebola, G. Saville, and W.A. Wakeham
Elsevier BV
Abstract The study of { x CH 4 + (1 − x )C 6 H 14 } presented here is part of a larger project that aims at the study of a prototype of a gas-condensate system, the ternary { x CH 4 + y C 6 H 14 + (1 − x − y )C 14 H 30 } . The experimental work was carried out in a semi-automated high-pressure high-temperature v.l.e. (vapour + liquid equilibrium) apparatus. It permits the determination of the compositions and densities of both phases of a hydrocarbon mixture, or even of a third phase if it happens to exist, in the range of pressure and temperature from (2 to 40) MPa and from ambient to 410 K, respectively. The precision of the mole fraction determination is ± 3 · 10 − 3 for the liquid phase and ± 2 · 10 − 3 for the vapour phase, while the density results have an uncertainty of no more than ± 0.8 kg · m − 3 , in both phases. The experimental measurements performed on { x CH 4 + (1 − x )C 6 H 14 } were carried out at two different temperatures, T = (348.15 and 383.15 ) K and over the range of pressures from 2 MPa up to the critical pressure of the mixture. The objective of the study of the system was the validation of the apparatus on the basis that it is a system on which extensive experimental data are available for comparison, although over a more restricted range of variables than those studied here. The experimental data have been compared with the representation given by a number of widely used thermodynamic models, namely the cubic equations of state of Peng–Robinson and of Soave–Redlich–Kwong and three corresponding states models, the Van der Waals one and two-fluid models.
M.J Cebola, G Saville, and W.A Wakeham
Elsevier BV
Maria-João Cebola, Krzysztof Chylinski, Graham Saville, and William Wakeham
Old City Publishing, Inc
Vapour-liquid equilibrium measurements have been performed on the binary system CH 4 -nC 6 H 14 at several temperatures over the pressure range 2-18MPa. The ternary system CH 4 -nC 6 H 14 -nC 14 H 30 was studied in the same temperature range and at three different pressures, 6.5, 9, and 12MPa over a range of concnetrations of C 14 H 30 from 0.002 to 0.05 in mole fraction. The results for both systems at one temperature have been compared with the predictions of two thermodynamic models, the Peng-Robinson equation of state and the one-fluid corresponding-states model.