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Garrido E.M.P.J.,Polytechnic Institute of Porto | Garrido J.M.P.J.,Polytechnic Institute of Porto | Milhazes N.,Instituto Superior Of Ciencias Of Saude Norte | Borges F.,University of Porto | Oliveira-Brett A.M.,University of Coimbra
Bioelectrochemistry | Year: 2010

Amphetamine and amphetamine-like drugs are popular recreational drugs of abuse because they are powerful stimulants of the central nervous system. Due to a dramatic increase in the abuse of methylenedioxylated derivatives, individually and/or in a mixture, and to the incoherent and contradictory interpretation of the electrochemical data available on this subject, a comprehensive study of the redox properties of amphetamine-like drugs was accomplished. The oxidative behaviour of amphetamine (A), methamphetamine (MA), methylenedioxyamphetamine (MDA) and methylenedioxymethamphetamine (MDMA) was studied in different buffer systems by cyclic, differential pulse and square-wave voltammetry using a glassy carbon electrode. A quantitative electroanalytical method was developed and successfully applied to the determination of MDMA in seized samples and in human serum. Validation parameters, such as sensitivity, precision and accuracy, were evaluated. The results found using the developed electroanalytical methodology enabled to gather some information about the content and amount of MDMA present in ecstasy tablets found in Portugal. Moreover, the data found in this study outlook the possibility of using the voltammetric methods to investigate the potential harmful effects of interaction between drugs such as MDMA and methamphetamine and other substances often used together in ecstasy tablets. © 2009 Elsevier B.V. All rights reserved.

Reis B.,Polytechnic Institute of Porto | Martins M.,Polytechnic Institute of Porto | Barreto B.,Polytechnic Institute of Porto | Milhazes N.,Instituto Superior Of Ciencias Of Saude Norte | And 7 more authors.
Journal of Agricultural and Food Chemistry | Year: 2010

The esterification of hydrophilic phenolic antioxidants is an efficient approach to enhance their solubility in apolar media. Herein, structureâ property studies on the antiradical activity of a series of protocatechuic acid alkyl esters have been accomplished. The increase of the lipophilicity was shown to significantly improve the antioxidant activity of protocatechuic esters. Their efficiency as radical scavengers was evaluated using distinctive analytical methods, namely, 2,2-diphenyl-1-picrylhydrazyl (DPPH) UV/visible method, electrochemistry, and differential scanning calorimetry. All the new alkyl protocatechuate antioxidants studied possessed better radical-scavenging capacity than the natural antioxidant protocatechuic acid. This work has shown that the alkyl ester side chain markedly influences the lipophilicity of this type of phenolic system without disturbing the core of the molecule responsible for antioxidant activity. The data on the antioxidant activity obtained using the different analytical methods correlated well with each other and have revealed the interesting antioxidant potential of alkyl esters of protocatechuic acid. © 2010 American Chemical Society.

Alcaro S.,University of Catanzaro | Gaspar A.,University of Porto | Gaspar A.,Instituto Superior Of Ciencias Of Saude Norte | Ortuso F.,University of Catanzaro | And 5 more authors.
Bioorganic and Medicinal Chemistry Letters | Year: 2010

Chromone carboxylic acids were evaluated as human monoamine oxidase A and B (hMAO-A and hMAO-B) inhibitors. The biological data indicated that only chromone-3-carboxylic acid is a potent hMAO-B inhibitor, with a high degree of selectivity for hMAO-B compared to hMAO-A. Conversely the chromone-2-carboxylic acid resulted almost inactive against both MAO isoforms. Docking experiments were performed to elucidate the reasons of the different MAO IC50 data and to explain the absence of activity versus selectivity, respectively. © 2010 Elsevier Ltd. All rights reserved.

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