Polytechnic Institute of Bragana

Portugal

Polytechnic Institute of Bragana

Portugal

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Santos C.M.M.,University of Aveiro | Santos C.M.M.,Polytechnic Institute of Bragana | Silva A.M.S.,University of Aveiro | Filipe P.,University of Lisbon | And 9 more authors.
Organic and Biomolecular Chemistry | Year: 2011

A structure-activity relationship has been established for eight hydroxy-2,3-diarylxanthones (XH) bearing hydroxy groups on the two aryl rings. One-electron oxidation by superoxide radical-anions (O2 -) and Trp radicals as well as reaction with CCl3O2 and CHCl2O2 radicals demonstrates that two OH groups are required for efficient antioxidant reactivity in cetyltrimethylammonium bromide micelles. Hydroxy groups at the meta and para positions on either of the two phenyl rings confer enhanced reactivity, but XH bearing an OH at the para position of either phenyl ring is unreactive. While oxidation is favoured by OH in both meta and para positions of 2-aryl xanthone substituents, addition of a third and/or fourth OH enhances electron-donating capacity. In Cu 2+-induced lipid peroxidation of human LDL, the lag period preceding the commencement of lipid peroxidation in the presence of XH bearing OH at meta and para positions on the 3-phenyl ring is extended to twice that observed with a comparable concentration of quercetin, a reference antioxidant. These antioxidants are also superior to quercetin in protecting human skin keratinocytes against tert-butylhydroperoxide-induced oxidative stress. While XH antioxidant activity in model biological systems is consistent with the structure-activity relationship, their response is also modulated by the localization of XH and by structural factors. © 2011 The Royal Society of Chemistry.


Amaral J.S.,University of Porto | Amaral J.S.,Polytechnic Institute of Bragana | Sepulveda M.,Laboratory of Separation and Reaction Engineering LSRE | Cateto C.A.,Laboratory of Separation and Reaction Engineering LSRE | And 5 more authors.
Polymer Degradation and Stability | Year: 2012

In this work, the ability of Aspergillus niger to degrade two lignin-based rigid polyurethane (RPU) foams was evaluated and compared with a control RPU foam based on a commercial polyether-polyol, Lupranol ® 3323. The foams degradation was studied according to different procedures, namely by setting different series of batch cultures, either using liquid media or soil conditions, for 90 days at 30°C. For the soil conditions, two different assays were performed, namely with and without A. niger addition. The changes in the morphology of the RPU foams were evaluated by optical (OM) and scanning electron microscopy (SEM), whereas the structural modifications were inspected by FTIR spectroscopy. After 90 days treatment, morphological changes were clearly visible at the surface (cell wall) of the two lignin-based foams indicating a stronger effect of the microorganisms' activity in these samples. FTIR spectra confirmed that the chemical structure of the polymer suffered modifications after the respirometry assays due to microorganisms attack. Comparatively to the commercial foam, it was observed that both the lignin-based foams presented a higher degradation level. © 2012 Elsevier Ltd. All rights reserved.


Gonalves M.F.,Royal University | Pereira J.A.,Polytechnic Institute of Bragana
Journal of Insect Science | Year: 2012

Arthropods are part of important functional groups in soil food webs. Recognizing these arthropods and understanding their function in the ecosystem as well as when they are active is essential to understanding their roles. In the present work, the abundance and diversity of soil arthropods is examined in olive groves in the northeast region of Portugal during the spring. Five classes of arthropods were found: Chilopoda, Malacostraca, Entognatha, Insecta, and Arachnida. Captures were numerically dominated by Collembola within Entognatha, representing 70.9% of total captures. Arachnida and Insecta classes represented about 20.4 and 9.0%, respectively. Among the predatory arthropods, the most representative groups were Araneae and Opiliones from Arachnida, and Formicidae, Carabidae, and Staphylinidae from Insecta. From the Formicidae family, Tetramorium semilaeve (Andre 1883), Tapinoma nigerrimum (Nylander 1856), and Crematogaster scutellaris (Olivier 1792) were the most representative ant species. Arthropods demonstrated preference during the day, with 74% of the total individuals recovered in this period, although richness and similarity were analogous during the day and night. © This is an open access paper. We use the Creative Commons Attribution 3.0 license that permits unrestricted use, provided that the paper is properly attributed.


Patoilo D.T.,University of Aveiro | Silva A.M.S.,University of Aveiro | Pinto D.C.G.A.,University of Aveiro | Santos C.M.M.,Polytechnic Institute of Bragana | And 2 more authors.
Tetrahedron Letters | Year: 2012

The Diels-Alder reaction of (E)-2-styrylchromones with a pyrimidine ortho-quinodimethane is reported for the first time. These cycloaddition reactions afford mixtures of two regioisomeric tetrahydroquinazoline-substituted chromones in moderate to excellent global yields. Irrespective of the substituents on the 2-styrylchromones, the 2-(7-aryl-4-methoxy-2-methyl-5,6,7,8- tetrahydroquinazolin-6-yl)chromone derivatives are always the major isomers. © 2012 Elsevier Ltd. All rights reserved.


Lopes R.P.,Polytechnic Institute of Bragana | Sernadela P.,Polytechnic Institute of Bragana
Advances in Intelligent Systems and Computing | Year: 2013

The Internet growth allowed an explosion of service provision in the cloud. The cloud paradigm dictates the users' information migration from the desktop into the network allowing access everywhere, anytime. This paradigm provided a adequate environment to the emergence of online storage services, such as Amazon S3. This kind of service allows storing digital data in a transparent way, in a pay-as-you-go model. This paper describes an implementation of an S3 compatible cloud storage service based on peer-to-peer networks, in particular, through the Bit- Torrent protocol. This approach allows taking advantage of the intrinsic features of this kind of networks, in particular the possibility for simultaneous downloading of pieces from different locations and the fault tolerance. © Springer International Publishing Switzerland 2013.


Vaz J.A.,University of Porto | Vaz J.A.,Polytechnic Institute of Bragana | Almeida G.M.,University of Porto | Ferreira I.C.F.R.,Polytechnic Institute of Bragana | And 2 more authors.
Food Chemistry | Year: 2012

Mushrooms are a possible rich source of biologically active compounds with the potential for drug discovery. The aim of this work was to gain further insight into the cytotoxicity mechanism of action of Clitocybe alexandri ethanolic extract against a lung cancer cell line (NCI-H460 cells). The effects on cell cycle profile and levels of apoptosis were evaluated by flow cytometry, and the effect on the expression levels of proteins related to cellular apoptosis was also investigated by Western blot. The extract was characterised regarding its phenolic composition by HPLC-DAD, and the identified compounds were studied regarding their growth inhibitory activity, by sulforhodamine B (SRB) assay. The effect of individual or combined compounds on viable cell number was also evaluated using the Trypan blue exclusion assay. It was observed that the C. alexandri extract induced an S-phase cell cycle arrest and increased the percentage of apoptotic cells. In addition, treatment with the GI 50 concentration (concentration that was able to cause 50% of cell growth inhibition; 24.8 μg/ml) for 48 h caused an increase in the levels of wt. p53, cleaved caspase-3 and cleaved poly (ADP-ribose) polymerase (PARP). The main components identified in this extract were protocatechuic, p-hydroxybenzoic and cinnamic acids. Cinnamic acid was found to be the most potent compound regarding cell growth inhibition. Nevertheless, it was verified that the concomitant use of the individual compounds provided the strongest decrease in viable cell number. Overall, evidence was found for alterations in cell cycle and apoptosis, involving p53 and caspase-3. Furthermore, our data suggests that the phenolic acids identified in the extract are at least partially responsible for the cytotoxicity induced by this mushroom extract. © 2011 Elsevier Ltd. All rights reserved.

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