L.F.Vilas Boas

Phenolic Compounds and Antioxidant Activity of Olea europaea L. Fruits and Leaves

Extracts of leaves, fruits and seeds of olive tree cultivars of Trás-os-Montes e Alto Douro (Portugal) were analysed by reverse phase HPLC with diode array detection and mass spectrometry (MS). This methodology allowed the identification of some common phenolic compounds, namely, verbascoside, rutin, luteolin-7-glucoside, oleuropein and hydroxytyrosol. Moreover the hyphenation of HPLC with MS enabled the identification of nüzhenide in olive seeds. An oleuropein glucoside was also detected in olive tree leaves. The total phenolic content was determined with the Folin Denis reagent and the total antioxidant activity with the ABTS method. There is a correlation between total antioxidant activity and total phenolic content with the exception of the seed extracts analysed. The apparent high antioxidant activity of seed extracts may be due to nüzhenide, a secoiridoid that is the major phenolic component of olive seeds. These results suggest a possible application of olive seeds as sources of natural antioxidants.

Oxovanadium(IV) and amino acids. I: The system L-alanine+VO2+; A potentiometric and spectroscopic study

Abstract The equilibria in aqueous solution in the system L -alanine+VO 2+ have been studied by a combination of pH-potentiometric and spectroscopic methods (EPR, visible absorption and circular dichroism) in the pH range 1.5–13. For pH > 4, high ligand to metal ratios were used. The results of the various methods are made self-consistent, then rationalized assuming an equilibrium model including the species MAH, MA, MAH −2 , MA 2 H 2 , MA 2 H, MA 2 , MA 2 H −1 , M 2 A 2 H −2 , M 2 A 2 H −3 (where HA denotes L -alanine) and several hydrolysis products; their formation constants and individual electronic spectra (isotropic and circular dichroism) are given. The isomerism arising from the combination of the lop-sided oxovanadium ion with the asymmetric carbon ligand is analysed.

Free Fatty Acids, Triglycerides and Volatile Compounds in Serra da Estrela Cheese—Changes throughout Ripening

The free fatty acids, triglycerides and volatile compounds in Serra da Estrela cheese were analysed and changes throughout ripening were examined. The free fatty acids showed a general increase until the 3rd week of ripening. The average total concentration of free fatty acids, 1123 mg kg-1, in cheese samples, was lower than other values published in the international literature for raw ewes’ milk cheese. The concentrations of triglycerides with carbon numbers smaller than C38 decreased during ripening. Twenty volatile aroma components were tentatively identified by static headspace gas chromatography using a flame ionization detector. Acetaldehyde and diacetyl, produced by indigeneous lactic acid bacteria, were detected. Ketones with 4–7 carbon atoms were also found.

Role of Chrysonilia sitophila in the quality of cork stoppers for sealing wine bottles.

The contribution of Chrysonilia sitophila in cork stopper manufacture was studied and a simulation of the industrial processing of cork stoppers was performed. Stoppers cut from slabs where mold development was inhibited were compared with others cut from slabs colonized by C. sitophila alone or with several molds, in terms of physical properties and chemical taints. C. sitophila does not produce 2,4,6-trichloroanisole, guaiacol, or 1-octene-3-ol on cork slabs incubated for 66 days. Since some chlorophenol-related compounds contaminate cork slabs during the production processes, metabolic tests were performed to investigate the capability of molds to produce 2,4,6-trichloroanisole by methylation of 2,4,6-trichlorophenol. Degradation of 2,4,6-trichlorophenol by C. sitophila resulted in a very high level of degradation without production of 2,4,6-trichloroanisole. C. sitophila restricted growth of other molds on maturing slabs for at least 30 days. These results show that C. sitophila can be exploited by industrial producers of cork stoppers since it is able to inhibit the development of other molds and it does not produce the compounds responsible for ‘cork-taint’, even in the presence of chlorophenols. Journal of Industrial Microbiology & Biotechnology (2000) 24, 256–261.

Oxovanadium(IV) and amino acids—II. The systems l-serine and l-threonine+VO2+. A potentiometric and spectroscopic study

Abstract The equilibria in aqueous solution in the systems l -serine and l -threonine +VO2+ have been studied by a combination of pH-potentiometric and spectroscopic methods (EPR, visible absorption and circular dichroism) in the pH range 1.5–13.6. For pH > 4, high ligand-to-metal ratios were used. The results of the various methods are made self-consistent, then rationalized assuming an equilibrium model including species, MLH, ML, MLH−2, MLH−3, ML2H2, ML2H, ML2, ML2H−1, ML2H−2, M2L2H−2 and M2L2H−3 (where HL denotes l -serine or l -threonine) and several hydrolysis products; their formation constants and individual electronic spectra (isotropic and circular dichroism) are given. Plausible isomeric structures for each of the stoichiometries are discussed.

Oxovanadium(IV) and amino acids—III. The system l-aspartic acid+vo2+; A potentiometric and spectroscopic study

Abstract The equilibria in the system l -aspartic acid +VO 2+ in aqueous solution for 1.5 ⪕ pH ⪕ 11 have been studied by a combination of pH-potentiometric and spectroscopic methods [electron paramagnetic resonance (EPR), visible absorption and circular dichroism (CD)]. For pH > 4, high ligand-to-metal ratios were used. The results of the various methods are made self-consistent, then rationalized assuming an equilibrium model including the species MDH 2 , MDH, MD, MD 2 H 3 , MD 2 H and MD 2 (where H 2 D denotes l - aspartic acid) and several hydrolysis products; their formation constants and individual electronic spectra (isotropic and CD) are given. Plausible isomeric structures for each of the stoichiometries are discussed.

Oxovanadium(IV) and amino acids—IV. The systems l-cysteine or d-penicillamine+VO2+; a potentiometric and spectroscopic study

Abstract The aqueous equilibria in the systems l -cysteine or d -penicillamine + VO2+ have been studied by a combination of pH-potentiometric and spectroscopic methods [electron paramagnetic resonance (EPR), visible absorption and circular dichroism (CD)] in the pH range 1.8–13.5. For pH > 4, high ligand-to-metal ratios were used. The results of the various methods are made self-consistent, then rationalized assuming an equilibrium model including species MLH2, ML2H4, ML2H3, ML2H2, ML2H, ML2, ML2H−1 and M2L2 (where H2L denotes either l -cysteine or d -penicillamine) and several hydrolysis products; their formation constants and individual electronic spectra (isotropic and CD) are given. Isomeric structures are discussed for each stoichiometry.

Organotin in the Tagus estuary

The tri(n-butyl)tin (TBT) moiety has been shown to have complex ecotoxicological effects on estuarine populations. In the Tagus the massive die-off of the Portuguese oyster (Crassostrea angulata Lmk), has been attributed to the introduction and use of this contaminant by shipyards. This paper reviews previous work by others and reassesses our results obtained in water and sediments of the Tagus estuary, as a contribution to the understanding of tin geochemistry and organotin speciation in this estuary. Contrary to earlier results, the latest surveys show that in the open waters of the Tagus measurable concentrations of all the three butyltin species occur, exhibiting peak concentrations at two locations that indicate two previously undetected sources of TBT. TBT also presents a peak concentration in sediments near the Lisnave shipyards, as previously suggested. The latest surveys still detected methylated forms of tin, particularly monomethyltin (Me Sn3+), in Tagus sediments, with maximum concentrations in the vicinity of urban effluent discharges. The concentrations for TBT and its degradation products found in the Tagus are potentially harmful to the populations of gastropods and endemic bivalves.

The system l-malic acid+oxovanadium(IV); a potentiometric and spectroscopic study

The equilibria in the system l-malic acid+oxovanadium(IV) in aqueous solution for 1 < pH < 12 have been studied by a combination of potentiometric and spectroscopic methods [electron paramagnetic resonance (EPR), visible absorption and circular dichroism (CD)]. The results of the various methods are made self-consistent in the region 1 ⪷ pH ⪷ 7, then rationalized assuming an equilibrium model including species MLH−2, MLH−1, ML, MLH, ML2H−2, ML2H−1, ML2, ML2H, ML2H2 (where H2L denotes l-malic acid and M is VO2+) and several hydrolysis products; their formation constants are given. Some other species were also detected in the region 7 ⪷ pH ⪷ 12.

The systems l-cysteine and d-penicillamine+ oxovanadium(IV); a potentiometric and spectroscopic study

Abstract The equilibria in the systems l -cysteine (and d -penicillamine) + VO 2+ in aqueous solution for 1.5 4, high ligand-to-metal ratios were used. The results of the various methods are made self-consistent, then rationalized assuming an equilibrium model including species MXH 2 ,MXH, MX 2 H 4 , MX 2 H 3 , MX 2 H 2 , MX 2 H, MX 2 , M 2 X 2 (where H 2 X denotes l -cysteine or d -penicillamine, and M denotes VO 2+ ), and several hydrolysis products; their formation constants and individual electronic spectra (isotropic and circular dichroism) are given. Plausible isomeric structures for each of the stoichiometries are discussed.