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A combined electrochemical quartz-crystal microbalance probe beam deflection(EQCM-PBD) study of solvent and ion transfers at a poly[Ni(saltMe)]: modified elecrode during redox switching IPB - Escola Superior Agrária
Vilas-Boas, Miguel; Henderson, M.J.; Freire, C.; Hillman, A.R.; Vieil, E..
The oxidative polymerization of the complex2,3-dimelhyl-N,N-bis( salicylidene)butane-2,3-diaminatonickel( n), [Ni(saltMe)], was monitored by the electrochemical quartz microbalance (EQCM) and crystal impedance techniques. Polymerisation efficiency was maintained throughout deposition of a film, which behaved rigidly, on the electrode.
Tipo: Article
Ano: 2000 URL: http://hdl.handle.net/10198/5889
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A new voltammetric tool for prppolis origin discrimination IPB - Escola Superior Agrária
Falcão, Soraia; Freire, C.; Vilas-Boas, Miguel.
The study of botanical extracts used in traditional medicinal have always captured researchers attention. Propolis (bee glue) is a sticky dark-colored material that honeybees collected from parts of plants, buds and exudates, mix it with wax and other secretions and use it as construction and defense material in the hive. Because its biological and pharmacological properties, is extensively used in foods and beverages with the purpose of maintain or improve human health.
Tipo: ConferenceObject
Ano: 2010 URL: http://hdl.handle.net/10198/5029
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Antioxidant activity of Agaricus sp mushrooms by chemical, biochemical and electrochemical assays IPB - Escola Superior Agrária
Barros, Lillian; Falcão, Soraia; Baptista, Paula; Freire, C.; Vilas-Boas, Miguel; Ferreira, Isabel C.F.R..
The antioxidant activity of five Agaricus sp. mushrooms was screened through chemical, biochemical and electrochemical techniques. The chemical assays allowed an evaluation of their reducing power and radical scavenging activity, while biochemical assays evaluated the lipid peroxidation inhibition capacity, using erythrocytes and brain cells as models; the electrochemical characterization of the mushrooms extracts were performed by cyclic voltammetry and differential pulse voltammetry. All the species proved to have antioxidant activity and particularly, by the electrochemical techniques, it has been shown that mushroom extracts revealed similar electrochemical responses, suggesting similar electroactive chemical composition, and oxidation potentials more...
Tipo: Article Palavras-chave: Agaricus sp mushrooms; Electrochemical assays; Lipid peroxidation inhibition.
Ano: 2008 URL: http://hdl.handle.net/10198/814
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Characterization of new phenolic derivatives in Portuguese propolis by electrospray mass spectroscopy IPB - Escola Superior Agrária
Falcão, Soraia; Vilas-Boas, Miguel; Freire, C.; Domingues, M.R.M.; Cardoso, Susana M..
This research outlines an extensive characterization of the phenolic composition of a propolis sample from the northeast of Porto gal. For that, ao ethanolic extract was prepared, fractionated by HPLC and the identification of the phenolic compounds was done by electro spray mass spectrometry in the negative mode. This technical approach allowed the identification of 37 phenolic compounds in the Portoguese propolis sample, including seven that were described for the first time. Two of these new compounds had [M-Hr ions at mlz 403, aod the others had [M-Hr ions at mlz 433, mlz 461, mlz 417, mlz 475, and mlz 565. In general, the molecular weight of these compounds was higher thao the common phenolic compounds of propolis aod their fragmentation pattern...
Tipo: ConferenceObject Palavras-chave: Propolis; Phenolic compounds; Mass spectrometry; Electrospray ionization.
Ano: 2009 URL: http://hdl.handle.net/10198/5265
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Characterization of new phenolic derivatives in Portuguese propolis by electrospray mass spectroscopy IPB - Escola Superior Agrária
Falcão, Soraia; Vilas-Boas, Miguel; Freire, C.; Domingues, M.R.M.; Cardoso, Susana M..
Propolis is a resinous substance collected by honeybees from tree buds, comprising plant exudates, secreted substances from bee metabolism, pollen and waxes. This product is widely used in traditional medicine [I] and it has recently gained popularity as a health food supplement. Currently, it is extensively used in foods and beverages, and it is claimed to improve health and prevent diseases such as inflammation, heart disease, diabetes and cancer.
Tipo: ConferenceObject
Ano: 2009 URL: http://hdl.handle.net/10198/5682
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Electrochemical and structural studies of nickel (II) Schiff base complexes derived from salicylaldehyde. Structural effects of bridge substituents on the stabilisation of the +3 oxidation state IPB - Escola Superior Agrária
Santos, I.C.; Vilas-Boas, Miguel; Piedade, M.F.M.; Freire, C.; Duarte, M.T.; Castro, B..
The oxidative chemistry of three Ni(II) complexes with Schiff base ligands derived from salicylaldehyde and diamines with different steric demands, N,N9-2-methylpropane-2,3-diyl-bis(salicylideneiminate)nickel(II) (1), N,N9-1,2-cyclohexyl-1,2-dyil-bis(salicylideneiminate)- nickel(II) (2) and N,N9-2,3-dimethylbutane-2,3-diyl-bis(salicylideneiminate)nickel(II) (3), was studied by cyclic voltammetry and chronoamperometry in N,N9-dimethylformamide and (CH3)2SO.
Tipo: Article
Ano: 2000 URL: http://hdl.handle.net/10198/5890
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Electrochemical behaviour of a new percursor for the design of Poly[Ni(saltMe)]: based modified electrodes IPB - Escola Superior Agrária
Vilas-Boas, Miguel; Santos, I.C.; Henderson, M.J.; Freire, C.; Hillman, A.R.; Vieil, E..
Wedescribe the potentiodynamic preparation and subsequent characterization of poly[Ni(3-MeOsaltMe)] films (surface concentration, 3 < ¡/nmol cm-2 < 350) in acetonitrile media. Coulometric and gravimetric (electrochemical quartz crystal microbalance, EQCM) data allow one to monitor the deposition process and show that the resultant films are physically and chemically stable.
Tipo: Article Palavras-chave: Modified electrodes; Salen.
Ano: 2003 URL: http://hdl.handle.net/10198/5887
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Electrochemical characterization of a novel salen type modified electrode IPB - Escola Superior Agrária
Vilas-Boas, Miguel; Freire, C.; Castro, B.; Hillman, A.R..
The nickel(II) complex with H2saltMe, a N2O2 Schiff base ligand derived from salicylaldehyde, was oxidatively electropolymerized on Pt electrodes in CH3CN/0.1 mol dm-3 tetraethylammonium perchlorate (TEAP) to generate polymer films that exhibit reversible oxidative electrochemical behavior in a wide potential range (0.0-1.3 V), high conductivity, and stability/durability.
Tipo: Article
Ano: 1998 URL: http://hdl.handle.net/10198/5886
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Evaluation of the antioxidant capacity of edible wild mushrooms by cyclic voltammetry IPB - Escola Superior Agrária
Falcão, Soraia; Barros, Lillian; Ferreira, Isabel C.F.R.; Freire, C.; Vilas-Boas, Miguel.
The problems of oxygen metabolism in humans constantly attract the attention. especially now that is obvious that the excess of oxygen and its reactive species cause radical-chain oxidation processes in cellular tissues, resulting in fast aging, cell destruction and incurable diseases. Cells are equipped with several defense systems which act through a variety of mechanisms, one of those is the protection through low-molecular weight antioxidants. like phenolic compounds
Tipo: ConferenceObject
Ano: 2008 URL: http://hdl.handle.net/10198/3553
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New Insigths into the structure and properties of electroactive polymer filmes derived from Ni(salen)polymer IPB - Escola Superior Agrária
Vilas-Boas, Miguel; Freire, C.; Castro, B.; Christensen, P.A.; Hillman, A.R..
Oxidative electrochemical polymerization of (N,N'-ethylenebis(salicylideneaminato)) nickel(II), [Ni(salen)], in acetonitrile/TEAP was reinvestigated. The polymers were characterized by in situ FTIR and UV-visible spectroscopies in order to explore film structure and to clarify the electronic states as a function of the electrochemically controlled applied redox potential; oxidized species involved in polymerization and oxidative switching of the polymer were also assessed by ex situ EPR experiments.
Tipo: Article
Ano: 1997 URL: http://hdl.handle.net/10198/5892
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Oxidation of ferrocene derivatives at a Poly[Ni(saltMe)] modified electrode IPB - Escola Superior Agrária
Vilas-Boas, Miguel; Pereira, E.M.; Freire, C.; Hillman, A.R..
The characterization of film permeability and mediation properties of poly[Ni(saltMe)] modified electrodes were evaluated by studying the oxidation of ferrocene and 1,1’-dimethylferrocene at these electrodes by rotating-disk voltammetry. The effects of varying the substrate and its solution concentration, film thickness, rotation speed and electrode potential on the limiting current density were analysed using the model of Albery.
Tipo: Article
Ano: 2002 URL: http://hdl.handle.net/10198/5885
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Propolis phenolic profile: a study in the atlantic islands of Azores IPB - Escola Superior Agrária
Falcão, Soraia; Cardoso, Susana M.; Domingues, M.R.M.; Freire, C.; Vilas-Boas, Miguel.
This work outlines a characterization of the phenolic composition of the Azorean islands propolis. For that, eleven samples from S. Miguel and Terceira islands, were extracted and characterized. According to the I-IPLC analysis, an samples showed a similar phenolic profile, with 37 compounds identified by ESI-MS analysis and UV spectra. Although the samples revealed a close phenolic composition, significant differences were found in their concentrations, probably due to variations in flora distribution around the beehive, and therefore, in resin availability for bees.
Tipo: ConferenceObject
Ano: 2010 URL: http://hdl.handle.net/10198/5267
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Propolis phenolic profile: a study in the Atlantic islands of Azores IPB - Escola Superior Agrária
Falcão, Soraia; Cardoso, Susana M.; Domingues, M.R.M.; Freire, C.; Vilas-Boas, Miguel.
Propolis it is a natural resinous substance that honeybees (Apis melifera, L.) collect from buds and exudates of plants and transformed in the presence of bee enzymes. This substance plays an important role in the hive as a construction and defence material due to its chemical and biological properties.[1] Propolis composition is extremely complex and dependent on its vegetal source, geographical location and climatic conditions. Typically this natural product includes resin (50%), beeswax (30%), essential oils (10%), pollen (5%) and other organic compounds (5%).[2] Due to the abundance in phenolic compounds (flavonoids, phenolic acids and their esters) and to its biological and pharmacological properties this group of substances became the target of many...
Tipo: ConferenceObject
Ano: 2010 URL: http://hdl.handle.net/10198/5023
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Screening of portuguese propolis and its plant sources for inhibitory activity against pathogenic protozoa IPB - Escola Superior Agrária
Vale, N.; Falcão, Soraia; Batista, V.; Freire, C.; Maes, L.; Vilas-Boas, Miguel.
Propolis is a beehive product with a very complex chemical composition, widely used in folk medicine because of its several therapeutic activities. Its biological properties and chemical composition may vary according to the geografic location and to the different plant sources. Recently, we reported the mechanism for extration and propolis sample preparation (Falca˜o et al, Anal. Bioanal. Chem., 2010, 396: 887-897). After that, we developed a new study for Portuguese propolis and plant samples found around the hive, and we present in this study the activity of these samples against pathogenic protozoa. Two different raw propolis samples from the northeast and centre of Portugal, both acquired from local beekeepers, were analysed in the present work. For...
Tipo: ConferenceObject
Ano: 2010 URL: http://hdl.handle.net/10198/5193
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Spectroelectrochemical characterisation of a poly[Ni(saltMe)] modified electrode IPB - Escola Superior Agrária
Vilas-Boas, Miguel; Freire, C.; Castro, B.; Christensen, P.A.; Hillman, A.R..
Electrogenerated polymers based on the nickel(II) compIex 2,3-dimetbyl- N,N -bis(salicylidene )butane-2,3- diaminatoniekel(II), poly[Ni(saltMe)], were characterized by in situ FTIR and UV/Vis spectroscopy and ex-situ EPR spectroscopy in order to gain insights into film structure, electronic states and charge conduction. The role of the nickel ions during film oxidation was probed by using EPR to study naturally abundant Ni and 61Ni-enriehed polymers.
Tipo: Article
Ano: 2001 URL: http://hdl.handle.net/10198/5888
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Spectroelectrochemical characterisation of copper salen-based polymer modified electrode IPB - Escola Superior Agrária
Martins, M.; Vilas-Boas, Miguel; Castro, B.; Hillman, A.R.; Freire, C..
Electrogenerated polymers based on copper salen-type complexes were characterised electrochemically and by in situ UV–vis and ex situ EPR spectroscopy. The films, poly[Cu(salen)] and poly[Cu(saltMe)], exhibit reversible oxidative electrochemical behaviour in a wide potential range (0.0–1.5 V). Different regimes for charge transport behaviour are accessed by manipulation of film thickness and experimental time scale: thin films (surface concentration, Γ < ca. 80 nmol cm−2) show thin-layer/surface behaviour in the scan rate range used (0.020–2.0 V s−1), whereas thicker polymers (Γ > ca. 90 nmol cm−2) exhibit a changeover from thin-layer to diffusion control regime at a critical scan rate that depends on polymer and film thickness: 0.15–0.20 V s−1 for...
Tipo: Article Palavras-chave: Conducting polymers; Polymerisation; Cyclic voltammetry; EPR spectroscopy; UV–vis spectroscopy.
Ano: 2005 URL: http://hdl.handle.net/10198/5819
Registros recuperados: 16
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