Santiuste J.M.,CSIC - Institute of Physical Chemistry "Rocasolano" |
Quintanilla-Lopez J.E.,CSIC - Institute of Physical Chemistry "Rocasolano" |
Quintanilla-Lopez J.E.,Institute of General Organic Chemistry |
Becerra R.,CSIC - Institute of Physical Chemistry "Rocasolano" |
And 2 more authors.
Chromatographia | Year: 2015
Isothermal retention indices (I) at 333–413 K on 12 stationary phases (SPs) covering a wide polarity range of a variety of volatile solutes belonging to 7 one-heteroatom chemical function series and 10 non-series solutes have been determined. The I values were computed with a method (LQG method) which does not require the determination of holdup times of the chromatographic column. I values of some compounds never before studied are reported. The influence on the retention indices of the column temperature, methylene number, and polarity of both the stationary phase and the solute has been studied. The solvation parameter model (SPM) as a function of I has been used for predicting I values, and for unraveling the influence of the polarity of stationary phase and solute on the retention indices. Seeley et al.’s formulation of the SPM has been used for quantifying the influence of polar and non-polar interactions on the I, and for checking the agreement between calculated and experimental values. According to our results, the I values obtained by the modified SPM can be considered equal to the experimental I values at the 99 % confidence level. © 2015, Springer-Verlag Berlin Heidelberg.
Gamboa-Santos J.,Autonomous University of Madrid |
Soria A.C.,Institute of General Organic Chemistry |
Corzo-Martinez M.,Autonomous University of Madrid |
Villamiel M.,Autonomous University of Madrid |
Montilla A.,Autonomous University of Madrid
Journal of Food and Nutrition Research | Year: 2012
A comprehensive study on physical and chemical quality parameters has been carried out on several highly consumed vegetables that were industrially dehydrated (carrot, onion, garlic and potato). The quality parameters determined were: dry matter, water activity, rehydration ratio, protein pattern, total polyphenols, saccharides and 2-furoylmethyl amino acid (2-FM-AA) content. After dehydration process, the main observed chemical change was the formation of 2-FM-AA, indicating the participation of amino acids (mainly lysine) in Maillard reaction evolution. With respect to the effect of 12-month storage under conditions usually used by consumers (in the dark, 19-27 °C, 15-41% relative humidity), with the exception of carrots, no remarkable amounts of 2-FM-AA were generated, in agreement with the slight variation in proteins pattern and saccharide composition. Particularly interesting is the case of onion and garlic, whose content of fructooligosaccharides (recognized prebiotic saccharides) was preserved during storage. Samples were also stable with regard to their polyphenol content and rehydration ability, showing the importance of sample pre-treatment, processing and storage conditions for preservation of bioactivity and overall quality of dehydrated vegetables. These results underline the usefulness of the indicators here determined for quality evaluation and the value of data reported for technologists, nutritionists and consumers. © 2012 VÚP Food Research Institute, Bratislava.
Gulias M.,University of Santiago de Compostela |
Lopez F.,Institute of General Organic Chemistry |
Mascarenas J.L.,University of Santiago de Compostela
Pure and Applied Chemistry | Year: 2011
We present a compilation of methodologies developed in our laboratories to assemble polycyclic structures containing small- and medium-sized cycles, relying on the use of transition-metal-catalyzed (TMC) cycloadditions. First, we discuss the use of alkylidene - cyclopropanes (ACPs) as 3C-atom partners, in particular in their Pd-catalyzed (3 + 2) cycloadditions with alkynes, alkenes, and allenes, reactions that lead to cyclopentane-containing polycyclic products in excellent yields. Then, we present the expansion of this chemistry to a (4 + 3) annulation with conjugated dienes, and to inter- and intramolecular (3 + 2 + 2) cycloadditions using external alkenes as additional 2C-π-systems. These reactions allow the preparation of different types of polycyclic structures containing cycloheptene rings, the topology of the products depending on the use of Pd or Ni catalysts. Finally, we include our more recent discoveries on the development of (4 + 3) and (4 + 2) intramolecular cyclo additions of allenes and dienes, promoted by Pt and Au catalysts, and discuss mechanistic insights supported by experimental and density functional theory (DFT) calculations. An enantioselective version of the (4 + 2) cycloaddition with phosphoramidite Au(I) catalysts is also presented. © 2011 IUPAC.
Perez-Fernandez V.,University of Alcala |
Gonzalez M.J.,Institute of General Organic Chemistry |
Garcia M.T.,University of Alcala |
Marina M.L.,University of Alcala
Analytica Chimica Acta | Year: 2013
A new CE method has been developed for the simultaneous separation of a group of parent phthalates. Due to the neutral character of these compounds, the addition of several bile salts as surfactants (sodium cholate (SC), sodium deoxycholate (SDC), sodium taurodeoxycholate (STDC), sodium taurocholate (STC)) to the separation buffer was explored showing the high potential of SDC as pseudostationary phase. However, the resolution of all the phthalates was not achieved when employing only this bile salt as additive, being necessary the addition of neutral cyclodextrins (CD) and organic modifiers to the separation media. The optimized cyclodextrin modified micellar electrokinetic chromatography (CD-MEKC) method consisted of the employ of a background electrolyte (BGE) containing 25. mM β-CD-100. mM SDC in a 100. mM borate buffer (pH 8.5) with a 10% (v/v) of acetonitrile, employing a voltage of 30. kV and a temperature of 25. °C. This separation medium enabled the total resolution of eight compounds and the partial resolution of two of the analytes, di-n-octyl phthalate (DNOP) and diethyl hexyl phthalate (DEHP) (Rs ~ 0.8), in only 12. min. The analytical characteristics of the developed method were studied showing their suitability for the determination of these compounds in commercial perfumes. In all the analyzed perfumes the most common phthalate was diethyl phthalate (DEP) that appeared in ten of the fifteen analyzed products. Also dimethyl phthalate (DMP), diallyl phthalate (DAP), dicyclohexyl phthalate (DCP), and di-n-pentyl phthalate (DNPP) were found in some of the analyzed samples. © 2013 Elsevier B.V.
Sanchez-Martin J.,CSIC - Institute for Sustainable Agriculture |
Heald J.,Aberystwyth University |
Kingston-Smith A.,Aberystwyth University |
Winters A.,Aberystwyth University |
And 4 more authors.
Plant, Cell and Environment | Year: 2015
Although a wealth of information is available on the induction of one or several drought-related responses in different species, little is known of how their timing, modulation and crucially integration influence drought tolerance. Based upon metabolomic changes in oat (Avena sativaL.), we have defined key processes involved in drought tolerance. During a time course of increasing water deficit, metabolites from leaf samples were profiled using direct infusion-electrospray mass spectroscopy (DI-ESI-MS) and high-performance liquid chromatography (HPLC) ESI-MS/MS and analysed using principal component analysis (PCA) and discriminant function analysis (DFA). The involvement of metabolite pathways was confirmed through targeted assays of key metabolites and physiological experiments. We demonstrate an early accumulation of salicylic acid (SA) influencing stomatal opening, photorespiration and antioxidant defences before any change in the relative water content. These changes are likely to maintain plant water status, with any photoinhibitory effect being counteracted by an efficient antioxidant capacity, thereby representing an integrated mechanism of drought tolerance in oats. We also discuss these changes in relation to those engaged at later points, consequence of the different water status in susceptible and resistant genotypes. Although a wealth of information is available on drought related responses, little is known about their timing, modulation and integration. Based on metabolomic changes in oat we demonstrate a novel role for salicylic acid in maintaining plant water status. This is coupled to induction of antioxidant and respiratory pathways to deal with the increasing oxidative stress promoted by the low CO2 concentration caused by partial stomatal closure. © 2014 John Wiley & Sons Ltd.