A critical review of the bioavailability of glucosinolates and related compounds

Glucosinolates (GLSs) are relatively inert (Z)-N-hydroximinosulfate esters, possessing a sulfur-linked beta-D-glucopyranose moiety and a variable side chain, found almost exclusively in cruciferous vegetables. Following cell disruption, they are hydrolysed by plant myrosinases, forming a group of chemically reactive and biologically active compounds. There is considerable evidence that these breakdown products, when consumed in the diet, may affect the risk of developing chronic diseases. However, in order for any compound to exert an activity in vivo, it is necessary to reach the site of action in an appropriate form and sufficient concentration. Deleterious and toxic effects may be observed at high concentrations: hence, bioavailability is a key factor defining the physiological, beneficial dose window of GLS hydrolysis products (GLS-HPs). For some GLS-HPs, this window can be rather narrow, and therefore is a critical parameter to be considered. In this review we critically evaluate the present state of knowledge on all factors that affect bioavailability of GLS-HPs. This includes liberation from the plant material, absorption from the digestive system, distribution around the body, metabolism and excretion.     

Set-valued average value at risk and its computation

New versions of the set-valued average value at risk for multivariate risks are introduced by generalizing the well-known certainty equivalent representation to the set-valued case. The first ’regulator’ version is independent from any market model whereas the second version, called the market extension, takes trading opportunities into account. Essential properties of both versions are proven and an algorithmic approach is provided which admits to compute the values of both versions over finite probability spaces. Several examples illustrate various features of the theoretical constructions.     

Multiresolution schemes for conservation laws

Summary. In recent years a variety of high–order schemes for the numerical solution of conservation laws has been developed. In general, these numerical methods involve expensive flux evaluations in order to resolve discontinuities accurately. But in large parts of the flow domain the solution is smooth. Hence in these regions an unexpensive finite difference scheme suffices. In order to reduce the number of expensive flux evaluations we employ a multiresolution strategy which is similar in spirit to an approach that has been proposed by A. Harten several years ago. Concrete ingredients of this methodology have been described so far essentially for problems in a single space dimension. In order to realize such concepts for problems with several spatial dimensions and boundary fitted meshes essential deviations from previous investigations appear to be necessary though. This concerns handling the more complex interrelations of fluxes across cell interfaces, the derivation of appropriate evolution equations for multiscale representations of cell averages, stability and convergence, quantifying the compression effects by suitable adapted multiscale transformations and last but not least laying grounds for ultimately avoiding the storage of data corresponding to a full global mesh for the highest level of resolution. The objective of this paper is to develop such ingredients for any spatial dimension and block structured meshes obtained as parametric images of Cartesian grids. We conclude with some numerical results for the two–dimensional Euler equations modeling hypersonic flow around a blunt body. Received June 24, 1998 / Revised version received February 21, 2000 / Published online November 8, 2000     

Transition‐Metal‐Free Formal Sonogashira Coupling and α‐Carbonyl Arylation Reactions

Transition‐metal‐free formal Sonogashira coupling and α‐carbonyl arylation reactions have been developed. These transformations are based on the nucleophilic aromatic substitution (S_NAr) of β‐carbonyl sulfones to electron‐deficient aryl fluorides, producing a key intermediate that, depending on the reaction conditions, gives the aromatic alkynes or α‐aryl carbonyl compounds. The development of these reactions is presented and, based on investigations under basic and acidic conditions, mechanisms have been proposed. To develop the formal Sonogashira coupling further, a milder, two‐step protocol is also disclosed that expands the reaction concept. The scope of these reactions is demonstrated for the synthesis of Sonogashira and α‐carbonyl arylated products from a range of electron‐deficient aryl fluorides with a variety of functional groups and aryl‐, heteroaryl‐, alkyl‐, and alkoxy‐substituted sulfone nucleophiles. These transition‐metal‐free reactions complement the metal‐catalyzed versions in terms of substitution patterns, simplicity, and reaction conditions.     

Enantioseparation of Aromatic β³-Amino acid by Precolumn Derivatization with o-Phthaldialdehyde and N-Isobutyryl-l-cysteine

In this study we describe the enantioseparation of aromatic β³-amino acids by precolumn derivatization with o-phthaldialdehyde and N-isobutyryl-l-cysteine. Derivatization conditions were studied in detail for (R,S)-β-phenylalanine and (R,S)-β-tyrosine revealing a reaction time of 1 min and a molar ratio of the reagents β^³-amino acid to o-phthaldialdehyde to N-isobutyryl-l-cysteine of 1:25:25 as optimal. The method was validated for (R,S)-β-phenylalanine in a bacterial cell extract. The analysis provided excellent specificity and reproducibility. The limit of quantification was 25 pmol per 0.5 μL injection. The method could be successfully transferred to the enantioseparation of other β^³-amino acids. Enantioseparation of all studied compounds could be achieved in 4–11 min.     

Cycling performance and efficiency of sulfonated poly(sulfone) membranes in vanadium redox flow batteries

As an alternative to Nafion® ion exchange membrane, an inexpensive commercially-available Radel® polymer was sulfonated, fabricated into a thin membrane, and evaluated for its performance in a vanadium redox flow battery (VRFB). The sulfonated Radel (S-Radel) membrane showed almost an order of magnitude lower permeability of VO²⁺ ions (2.07 × 10^?7 cm²/min), compared to Nafion 117 (1.29 × 10^?6 cm²/min), resulting in better coulombic efficiency (~ 98% vs. 95% at 50 mA/cm²) and lower capacity loss per cycle. Even though the S-Radel membrane had a slightly higher membrane resistance, the energy efficiency of the VRFB with the S-Radel membrane was comparable to that of Nafion because of its better coulombic efficiency resulting from the lower vanadium ion crossover. The S-Radel membrane exhibited good performance up to 40 cycles, but a decline in performance at later cycles was observed, likely as a result of membrane degradation.