HPLC/DAD/MS and antioxidant activity of isoflavone-based food supplements

Isoflavones are polyphenolic compounds found mainly in legumes the benefits of which have been widely studied and attributed in particular to their phytoestrogenic activity. The aim of this study was to evaluate the quali-quantitative composition of food supplements based on soy isoflavones (Glycine max L.) and red clover (Trifolium pratense). Six commercial food supplements (five soy-based and one red clover-based) were analyzed by HPLC/DAD/MS. Genistein, daidzein, glycitein, biochanin A and formononetin derivatives (glycosides and acylglycosides) were identified in the analyzed samples. Also the antiradical activities (towards the DPPH* radical) and Fe2+ chelating abilities were compared.     

Shear stresses in elastic beams: an intrinsic approach

The theory of non-uniform flexure and torsion of Saint-Venant's beam with arbitrary multiply connected cross section is revisited in a coordinate-free form to provide a computationally convenient context. Numerical implementations, by Matlab, are performed to evaluate the maximum elastic shear stresses in beams with rectangular cross sections for different Poisson's ratios. The deviations between the maximum and mean stresses are then diagrammed to adjust the results provided by Jourawski's method.     

Perturbations produced by electrospray ionization mass spectrometry in the speciation of aluminium(III)/1,6‐dimethyl‐4‐hydroxy‐3‐pyridinecarboxylate aqueous solutions

Electrospray ionization mass spectrometry (ESI‐MS) is very often employed to study metal/ligand equilibria in aqueous solution. However, the ionization process can introduce perturbations which affect the speciation results in an unpredictable way. It is necessary to identify these perturbations in order to correctly interpret the ESI‐MS speciation results. Aluminium(III)/1,6‐dimethyl‐4‐hydroxy‐3‐pyridinecarboxylate (DQ716) aqueous solutions at various pH were analysed by ESI‐MS, and speciation results were compared with those obtained by equilibrium techniques. Differences observed were both qualitative and quantitative. The ESI‐MS spectral changes due to different settings of the following instrumental parameters were analyzed: the solution flow rate (F_S), the nebulizer gas flow rate (F_G), the potential applied at the entrance capillary (E_C), and the temperature of the drying gas (T_G). The effects produced by F_S and E_C on the spectra strongly suggest the key role of surface activity in determining the relative fraction of the ions reaching the detector. The experimental effects of F_S and T_G were interpreted considering the presence of at least two reactions in the gas phase and a dimerization occurring in the droplets. These perturbations cannot be generalized because they appear to be chemical system‐related and instrument‐dependent. Therefore, the identification of perturbations is a required task for any metal‐ligand equilibrium study performed by ESI‐MS. Our results indicate that perturbations can be identified by evaluating the effects produced in the spectra by a change of instrumental parameters. Copyright © 2010 John Wiley & Sons, Ltd.     

Schwarz reflection geometry I: Continuous iteration of reflection

Differential equations are derived for a continous limit of iterated Schwarzian reflection of analytic curves, and solutions are interpreted as geodesics in an infinite-dimensional symmetric space geometry. Mathematics Subject Classification (1991):53C35, 53A30, 30D05.     

Insertion Reactions of 1,2‐Disubstituted Olefins with an α‐Diimine Palladium(II) Complex

The migratory insertions of cis or trans olefins CH(X)?CH(Me) (X = Ph, Br, or Et) into the metal–acyl bond of the complex [Pd(Me)(CO)(ⁱPr₂dab)]⁺ [B{3,5‐(CF₃)₂C₆H₃}₄]^? ( 1 ) (ⁱPr₂dab = 1,4‐diisopropyl‐1,4‐diazabuta‐1,3‐diene = N,N′‐(ethane‐1,2‐diylidene)bis[1‐methylethanamine]) are described (Scheme 1). The resulting five‐membered palladacycles were characterized by NMR spectroscopy and X‐ray analysis. Experimental data reveal some important aspects concerning the regio‐ and stereochemistry of the insertion process. In particular, the presence of a Ph or Br substituent at the alkene leads to the formation of highly regiospecific products. Moreover, in all cases, the geometry of the substituents in the formed palladacycle was the same as in the starting olefin, as a consequence of a cis addition of the Pd–acyl fragment to the C?C bond. Reaction with CO and MeOH of the five‐membered complex derived from trans‐β‐methylstyrene (= [(1E)‐prop‐1‐enyl]benzene) insertion, yielded the 2,3‐substituted γ‐keto ester 9 with an (2RS,3SR)‐configuration (Scheme 3).     

Stereocontrol in alkyne cyclocarbonylation reactions promoted by a bioxazoline palladium(II) complex

Insertion of 1,2-disubstituted alkynes into [Pd(CH3)(CO)(BIOX)]+[B{3,5-(CF3)2C6H3}4]- (1), where BIOX=(4S,4'S)-(-)-4,4',5,5'-tetrahydro-4,4'-bis(1-methylethyl)-2,2'-bioxazole, leads to the formation of five-membered palladacycles, which, by reaction with carbon monoxide, produce a mixture of two diastereomeric forms of a palladium complex containing an eta3-allylic gamma-lactone ligand. On leaving the mixture in solution, one isomer was converted into the other, reaching a diastereomeric excess of up to 94 %. The steric and electronic factors responsible for the epimerization process were investigated by theoretical methods. Cleavage of the eta3-allyl--palladium bond by nucleophiles allowed highly substituted chiral butenolides to be synthesized in good enantiomeric excess.     

Liquid chromatographic determination of Alternaria toxins in carrots

A liquid chromatographic (LC) method was developed for the determination of Alternaria radicina and A. alternata toxins in carrots. Toxins were extracted from carrot with an acidified mixture of water-methanol-acetonitrile. The filtered extract was divided in 2 parts that were purified by solid-phase extraction on a C18 column for the analysis of radicinin (RAD), altertoxin-I (ATX-I), alternariol (AOH), and alternariol methyl ether (AME), and on a polymeric Oasis HLB column for tenuazonic acid (TeA). Toxins were quantified by reversed-phase LC with UV diode array detection by using 2 consecutive isocratic mixtures of acetonitrile-sodium dihydrogen phosphate solution. Mean recoveries of TeA, ATX-I, AME, RAD, and AOH from carrots spiked at levels between 0.5 and 3.0 microg/g were 69, 71, 90, 36, and 78%, with mean within-laboratory repeatability of 14, 5, 4, 6, and 18%, respectively. The mean between-laboratory reproducibilities for the determination of TeA, ATX-I, AME, and RAD in spiked samples were 25, 22, 6, and 12%, respectively. Limits of detection (signal-to-noise ratio of 3) for RAD, TeA, ATX-I, AME, and AOH were 0.006, 0.02, 0.02, 0.01, and 0.005 microg/g, respectively. RAD was detected (0.16-13.9 microg/g) in 3 out of 266 carrot samples produced under organic conditions in 3 European locations, whereas A. alternata mycotoxins were not found in any tested samples.     

TR-EPR of single and double spin-labeled C60 derivatives in frozen matrices

Time-resolved electron paramagnetic resonance spectra of two single spin-labeled and two double spin-labeled C₆₀ derivatives in frozen solution are recorded with pulsed laser excitation and 100 ns time resolution. Quartet and quintet excited species are detected which arise from the electron spin coupling of the triplet excited fullerene moiety with the unpaired spin(s) of the nitroxide label(s). Despite the similar molecular structure, in both series of single and double labeled derivatives a different behavior was found, which is due to substantial difference of the energy of exchange coupling.