Papers by Armando Silvestre
New Journal of Chemistry, 2001
Lipids, Apr 1, 2005
The wood and bark of four Acacia species growing in Portugal, namely, A. longifolia, A. dealbata,... more The wood and bark of four Acacia species growing in Portugal, namely, A. longifolia, A. dealbata, A. melanoxylon, and A. retinodes, were investigated for their sterol content. The lipids fractions of the different wood and bark samples were isolated, and the sterols were identified and quantified by GC-MS. Two delta7 sterols, specifically, spinasterol and dihydrospinasterol, were the main sterols found in considerable amounts, particularly in wood tissues (more than 0.5 g/kg of dry wood in the case of A. melanoxylon and A. retinodes). The corresponding unusual steryl glucosides were also identified in significant amounts in the wood and bark extracts.
Cheminform, 2010
ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance t... more ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
Journal of Agricultural and Food Chemistry, May 1, 2010
The behavior of Miscanthus x giganteus bark lipophilic extractives during three acid organosolv p... more The behavior of Miscanthus x giganteus bark lipophilic extractives during three acid organosolv pulping processes (Acetosolv, formic acid fractionation, and Milox) was investigated. It was demonstrated that nearly 90% of the lipophilic extractives were removed from pulps by either dissolution in the organosolv liquors (fatty acids and alcohols) or extensive degradation (sterols). The organosolv liquors were found to be rich in vanillin, syringaldehyde, and ferulic, vanillic, and p-coumaric acids. The Acetosolv fractionation process was found to be the most efficient in the removal of lipophilic components from pulps, and it was also the process that generated higher amounts of valuable monomeric phenolic compounds that could be exploited within the biorefinery context. . J. J. Villaverde thanks Fundac -ão para a Ciência e a Tecnologia (FCT) for the award of a postdoctoral grant.
Applied Spectroscopy, Aug 1, 2009
The use of trichloroacetyl isocyanate (TAI) to mark both hydroxyl and carboxyl groups borne by th... more The use of trichloroacetyl isocyanate (TAI) to mark both hydroxyl and carboxyl groups borne by the hydrolysis or methanolysis of suberin fragments (a complex mixture of hydroxy fatty acids), allowed the quantitative assessment of the ratio between carboxyl and hydroxy groups, as well as the ratio between primary and secondary hydroxy groups, to be carried out reliably by 1H nuclear magnetic resonance (NMR) spectroscopy. All the samples thus analyzed displayed an excess of CO2H (or CO2CH3) functions with respect to the OH counterparts, albeit to a variable extent, depending on the procedure adopted to isolate the suberin fragments. The precise knowledge of the molar ratio of these two reactive moieties is fundamental for the correct utilization of suberin monomers in polymerization reactions leading to aliphatic polyesters.
Phytochem Analysis, 2005
The chemical composition of the epicuticular wax from the fruits of Eucalyptus globulus was studi... more The chemical composition of the epicuticular wax from the fruits of Eucalyptus globulus was studied by GC-MS before and after alkaline hydrolysis. The wax had two main components, ursolic acid and tritriacontan-16,18-dione, together with several other triterpenic acids. After alkaline hydrolysis, a large increase in the amounts of triterpenic acids and fatty acids (particularly in hexadecanoic acid) was observed, suggesting that these components were present predominantly in esterified forms in the fruit wax. Six compounds were isolated from the fruits by preparative chromatography, and were identified as 8-desmethyleucalyptin, sesamin, tritriacontan-16,18-dione, ursolic acid, 3beta-hydroxyurs-11-en-13beta(28)-olide (ursolic acid lactone) and 3beta,11alpha-dihydroxyurs-12-en-28-oic acid, the latter of which was identified for the first time.
Lipids, 2005
The wood and bark of four Acacia species growing in Portugal, namely, A. longifolia, A. dealbata,... more The wood and bark of four Acacia species growing in Portugal, namely, A. longifolia, A. dealbata, A. melanoxylon, and A. retinodes, were investigated for their sterol content. The lipids fractions of the different wood and bark samples were isolated, and the sterols were identified and quantified by GC-MS. Two ∆ 7 sterols, specifically, spinasterol and dihydrospinasterol, were the main sterols found in considerable amounts, particularly in wood tissues (more than 0.5 g/kg of dry wood in the case of A. melanoxylon and A. retinodes). The corresponding unusual steryl glucosides were also identified in significant amounts in the wood and bark extracts.
Journal of Wood Chemistry and Technology, Feb 16, 2007
... delignification. ACKNOWLEDGMENTS The authors thank FCT-PRAXIS XXI for the financial support o... more ... delignification. ACKNOWLEDGMENTS The authors thank FCT-PRAXIS XXI for the financial support of the research project 3/3.2/PAPEL/2327/95 and for the awarding of a research grant (BIC/3700/96) to Paula Pinto. The authors ...
Separation and Purification Technology, Sep 24, 2010
To explore proper extractive solvents and to design an optimized separation process it is highly ... more To explore proper extractive solvents and to design an optimized separation process it is highly imperative to understand the molecular-based phenomena governing the solutes partitioning. Moreover, the development of new techniques for the biomolecules separation and purification, while maintaining their functional characteristics unchanged, is still ongoing. Therefore, in this work, the partition coefficients of vanillin, a compound with well-known organoleptic
Bioresource Technol, 2006
The effects of oxygen (O), ozone (Z) and hydrogen peroxide (P) bleaching stages on the compositio... more The effects of oxygen (O), ozone (Z) and hydrogen peroxide (P) bleaching stages on the composition and total amount of Eucalyptus globulus kraft pulp lipophilic extractives was studied.
Disruption of the three-dimensional network of suberin in cork by cholinium hexanoate leads to it... more Disruption of the three-dimensional network of suberin in cork by cholinium hexanoate leads to its efficient and selective isolation. The reaction mechanism, which likely involves selective cleavage of some intermonomeric bonds in suberin, was still unanswered. To address this question, the role of the ionic liquid during suberin depolymerisation and during cleavage of standard compounds carrying key chemical functionalities was herein investigated. A clear demonstration that the ionic liquid catalyses the hydrolysis of acylglycerol ester bonds was attained herein, both experimentally and computationally (DFT calculations). This behaviour is related to cholinium hexanoate capacity to activate the nucleophilic attack of water. The data showed also that the most favourable reaction is the hydrolysis of acylglycerol ester bonds, with the C2 position reporting the faster kinetics, whilst most of the linear aliphatic esters remained intact. The study emphasises that the ionic liquid plays the dual role of solvent and catalyst and leads to suberin efficient extraction through a mild depolymerisation. It is also one of the few reports of ionic liquids as efficient catalysts in the hydrolysis of esters.
... Andreia F. Sousa, Paula CRO Pinto, Armando JD Silvestre, Carlos Pascoal Neto CICECO and Depar... more ... Andreia F. Sousa, Paula CRO Pinto, Armando JD Silvestre, Carlos Pascoal Neto CICECO and Department of Chemistry, University of Aveiro, 3810-193 Aveiro ... 27. Pelillo, M.; Iafelice, G.; Marconi, E.; Caboni, MF Rap. ... Cordeiro N.; Belgacem MN; Gandini A.; Pascoal Neto C. Ind. ...
Journal of Pulp and Paper Science
... SILVESTRE AJD (1) ; PEREIRA CCL (1) ; NETO C. Pascoal (1) ; EVTUGUIN DV (1) ; CAVALEIROJAS (1... more ... SILVESTRE AJD (1) ; PEREIRA CCL (1) ; NETO C. Pascoal (1) ; EVTUGUIN DV (1) ; CAVALEIROJAS (1) ; ... La liqueur noire de la cuisson de E.globulus a ??t?? extraite de fa??on s??quentielle avec de l'??ther ??thylique ?? des pH de 12, 7 et 2, suivi d'ac??tate d'??thyle ?? un pH de 2. Un ...
Appita Journal
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This study investigates the effect of pulping time and process parameters on the content of hexen... more This study investigates the effect of pulping time and process parameters on the content of hexenuronic acid (HexA) in Eucalyptus globulus kraft pulps. Under selected standard pulping conditions, the amount of HexA in pulps increases during cooking. This behavior, significantly ...
Journal of Pulp and Paper Science
ABSTRACT
Acylation of cellulose fibers with fatty acids constitute an interesting way to produce biodegrad... more Acylation of cellulose fibers with fatty acids constitute an interesting way to produce biodegradable plastics,4 as well as to obtain reinforcing materials for composites with common polymeric matrices5 like polyethylene. The cellulose modification reactions can be performed in ...
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Papers by Armando Silvestre