Johan Van der Eycken

Sodium tetra(n-propyl)borate: a novel aqueous in situ derivatization reagent for the simultaneous determination of organomercury, -lead and -tin compounds with capillary gas chromatography–inductively coupled plasma mass spectrometry

Abstract The versatility of sodium tetra(n-propyl)borate, NaBPr4, as aqueous in situ derivatization reagent for organometallic compounds is demonstrated. With this new derivatization reagent it is now possible to derivatize the important ethyl derivatives of lead and mercury which until now had to be derivatized by Grignard alkylation or hydride generation. The synthesis of NaBPr4 is described in detail. Derivatization parameters such as pH, reaction time, amount of reagent and stability of the aqueous NaBPr4 solution were investigated. Different organometallic compounds of tin, mercury and lead were simultaneously determined by an inductively coupled plasma mass spectrometer coupled to the capillary GC system using a laboratory-developed interface. Good linearity was obtained for all components with detection limits in the ng/l range (without preconcentration). The reproducibility of the complete procedure, i.e. derivatization, extraction and injection, is better than 10% R.S.D. The analysis of the PACS-1 Reference Material after derivatization with NaBPr4 showed the accuracy of this method.

Phenolic profiling of caffeic acid O-methyltransferase-deficient poplar reveals novel benzodioxane oligolignols.

Caffeic acid O-methyltransferase (COMT) catalyzes preferentially the methylation of 5-hydroxyconiferaldehyde to sinapaldehyde in monolignol biosynthesis. Here, we have compared HPLC profiles of the methanol-soluble phenolics fraction of xylem tissue from COMT-deficient and control poplars (Populus spp.), using statistical analysis of the peak heights. COMT down-regulation results in significant concentration differences for 25 of the 91 analyzed peaks. Eight peaks were exclusively detected in COMT-deficient poplar, of which four could be purified for further identification using mass spectrometry/mass spectrometry, nuclear magnetic resonance, and spiking of synthesized reference compounds. These new compounds were derived from 5-hydroxyconiferyl alcohol or 5-hydroxyconiferaldehyde and were characterized by benzodioxane moieties, a structural type that is also increased in the lignins of COMT-deficient plants. One of these four benzodioxanes amounted to the most abundant oligolignol in the HPLC profile. Furthermore, all of the differentially accumulating oligolignols involving sinapyl units were either reduced in abundance or undetectable. The concentration levels of all identified oligolignols were in agreement with the relative supply of monolignols and with their chemical coupling propensities, which supports the random coupling hypothesis. Chiral HPLC analysis of the most abundant benzodioxane dimer revealed the presence of both enantiomers in equal amounts, indicating that they were formed by radical coupling reactions under simple chemical control rather than guided by dirigent proteins.

Novel method for simultaneous determination of p-cresylsulphate and p-cresylglucuronide: clinical data and pathophysiological implications

BACKGROUND The uraemic retention solutes p-cresylsulphate (pCS) and p-cresylglucuronide (pCG), two conjugates of p-cresol, were never determined simultaneously. In the present paper, a high-performance liquid chromatography (HPLC) method was developed and used to quantify both compounds in parallel in an in vivo observational study and their in vitro effect was evaluated by flow cytometry. METHODS pCS and pCG were determined in serum. For the validation specificity, linearity, recovery, precision and the quantification limit were evaluated. In vivo, concentrations of both compounds were determined in 15 controls and 77 haemodialysis patients, as well as protein binding in the dialysed group and the reduction ratios during haemodiafiltration. In addition, the in vitro effect of the solutes on leucocyte free radical production at measured concentrations was assessed. RESULTS A fast and accurate HPLC method was developed to simultaneously quantify pCS and pCG. Both conjugates are retained in uraemia with a substantially higher total serum pCS in comparison to pCG (31.4 ± 15.8 versus 7.3 ± 6.5 mg/L) but also a substantial difference in protein binding (92.4 ± 3.0 versus 8.3 ± 4.4%) and in reduction ratio during post-dilution haemodiafiltration (37.4 ± 7.1 versus 78.6 ± 6.4%). pCG per se has no effect on leucocyte oxidative burst activity, whereas in combination with pCS, a synergistic activating effect was observed. CONCLUSIONS Serum concentrations of pCS and pCG are elevated in uraemia. Both conjugates show a different protein binding, resulting in a different dialytic behaviour. Biologically, both conjugates are synergistic in activating leucocytes.

Prospective Evaluation of the Change of Predialysis Protein-Bound Uremic Solute Concentration With Postdilution Online Hemodiafiltration

Although protein-bound uremic compounds have been related to outcome in observational studies, few current dialysis strategies provide more removal of those compounds than standard hemodialysis. We evaluated the evolution of protein-bound uremic solutes after a switch from high-flux hemodialysis to postdilution hemodiafiltration (n = 13). We compared predialysis solute concentration at 4, 5, and 9 weeks versus baseline for several protein-bound compounds and water-soluble solutes, as well as for beta(2)-microglobulin. After 9 weeks of postdilution hemodiafiltration, a significant decrease versus baseline could be detected for total concentration of protein-bound solutes: p-cresylsulfate (3.98 +/- 1.51-3.17 +/- 1.77 mg/dL, -20%, P < 0.01) and 3-carboxyl-4-methyl-5-propyl-2-furanpropionic acid (0.72 +/- 0.52-0.64 +/- 0.46 mg/dL, -11%, P < 0.01). For the other protein-bound solutes, hippuric acid, indoleacetic acid, and indoxylsulfate, no change in total concentration could be detected. The concentration of the middle molecule, beta(2)-microglobulin, decreased as well after 9 weeks of postdilution hemodiafiltration (24.7 +/- 9.3-18.1 +/- 6.7 mg/L, -27%, P < 0.01). For water-soluble compounds, no significant change of concentration was found. Postdilution hemodiafiltration in comparison to high-flux hemodialysis provided significant reduction of predialysis concentration of protein-bound compounds, especially those with the highest protein binding, and of beta(2)-microglobulin, by -11 to -27% in 9 weeks.

Distribution of soy-derived phytoestrogens in human breast tissue and biological fluids.

OBJECTIVE: Soy-derived phytoestrogens may exert several health-beneficial effects. Although plasma and urine levels of these compounds after ingestion have been thoroughly investigated, little is known about their tissue distribution, which is particularly important for tissues with high endogenous estrogen and estrogen receptor concentrations. We aimed to investigate the concentrations of genistein, daidzein, and equol in human breast tissue homogenate and to compare these with the corresponding values in serum and urine. METHODS: A randomized, double-blind, placebo-controlled study was undertaken to evaluate the concentrations of soy-derived phytoestrogens achieved in breast tissue homogenate, serum, and urine after ingestion of either a soy-based food supplement (n = 9) or a placebo tablet (n = 19) for 5 consecutive evenings before aesthetic breast surgery. To account for the heterogeneity of the breast tissue samples, markers for cellularity, epithelial content, blood vessel content, and total fat were determined. RESULTS: Urine concentrations of genistein, daidzein, and equol were significantly higher in the soy-supplemented subjects than in the subjects ingesting the placebo (P < .05). Only genistein was found to be significantly higher in serum of the soy group than in the placebo group, and no significant differences were found in breast tissue homogenate concentrations of all analytes between the 2 groups. CONCLUSION: Intake of soy-based food supplements for 5 consecutive days did not result in significantly higher genistein, daidzein, and equol concentrations in breast tissue homogenate when compared with the placebo group. The concentrations were in the low nanomolar range, whereas in the corresponding serum samples, concentrations were a hundred-fold higher. LEVEL OF EVIDENCE: I

Alkyl-lysophospholipid 1-O-octadecyl-2-O-methyl- glycerophosphocholine induces invasion through episialin-mediated neutralization of E-cadherin in human mammary MCF-7 cells in vitro.

1‐O‐octadecyl‐2‐O‐methyl‐glycerophosphocholine (ET‐18‐OMe) is an analogue of the naturally occurring 2‐lysophosphatidylcholine belonging to the class of antitumor lipids. Previously, we demonstrated that ET‐18‐OMe modulates cell‐cell adhesion of human breast cancer MCF‐7 cells. In the present study, we tested the effect of ET‐18‐OMe on adhesion, invasion and localisation of episialin and E‐cadherin in MCF‐7/AZ cells expressing a functional E‐cadherin/catenin complex. The MCF‐7/6 human breast cancer cells were used as negative control since their E‐cadherin/catenin complex is functional in cells grown on solid substrate but not in suspension. The function of E‐cadherin, a calcium‐dependent transmembrane cell‐cell adhesion and signal‐transducing molecule, is disturbed in invasive cancers by mutation, loss of mRNA stability, proteolytic degradation, tyrosine phosphorylation of associated proteins and large cell‐associated proteoglycans or mucin‐like molecules such as episialin. Episialin, also called MUC1, is an anti‐adhesion molecule that by its large number of glycosylated tandem repeats can sterically hinder the adhesive properties of other glycoproteins. ET‐18‐OMe inhibited the E‐cadherin functions of MCF‐7/AZ cells as measured by inhibition of fast and slow aggregation and by the induction of collagen invasion. These effects were enhanced by MB2, an antibody against E‐cadherin and blocked by monoclonal antibodies (MAbs) 214D4 or M8 against episialin. ET‐18‐OMe had no influence on tyrosine phosphorylation of β‐catenin and the E‐cadherin/catenin complex remained intact. Transcription, translation, protein turnover and cell surface localisation of episialin were not altered. ET‐18‐OMe induced finger‐like extensions with clustering of episialin together with E‐cadherin and carcinoembryonic antigen but not with occludin. In cells in suspension, ET‐18‐OMe caused a shift in the flow‐cytometric profile of episialin toward a lower intensity for MCF‐7/AZ cells. In contrast with MCF‐7/AZ cells, the adhesion‐deficient and noninvasive MCF‐7/6 cells showed neither morphotypic changes nor induction of aggregation nor invasion in collagen I upon treatment with ET‐18‐OMe. Co‐localisation of episialin with E‐cadherin was rarely observed. We conclude that in the human breast cancer cells MCF‐7/AZ, E‐cadherin and episialin are key molecular players in the regulation of promotion and suppression of cell‐cell adhesion and invasion.

Synthesis and characterization of the N-terminal acetylated 17-23 fragment of thymosin beta 4 identified in TB-500, a product suspected to possess doping potential

The formulation TB-500 is suspected to be used as doping agent in sport. This work describes the detection and the identification of the N-terminal acetylated 17-23 fragment of human thymosin beta 4 (Ac-LKKTETQ) in TB-500 by means of high-performance liquid chromatography/high resolution mass spectrometry using an Orbitrap Exactive benchtop mass spectrometer. Ac-LKKTETQ was also synthesized by solid-phase peptide synthesis, and an analytical strategy for detection in plasma and urine by high-performance liquid chromatography/low resolution triple-quadrupole mass spectrometry was suggested.

Supported gold nanoparticles as efficient and reusable heterogeneous catalyst for cycloisomerization reactions

We report the utilization of a novel catalyst for cycloisomerizations. The novel catalyst system contains gold nanoparticles supported on Al-SBA15, which was prepared by the ball-milling process. We developed a greener methodology for synthesizing spiroindolines under heterogeneous conditions, using this novel class of supported gold nanoparticles in combination with microwave irradiation. The catalyst is highly reusable and selective. Cycloisomerization reaction yields ranged from good to excellent leading to the formation of two novel classes of six- and seven-membered heterocycles, which have been unprecedented so far. The selectivity of the catalyst towards the desired products is high and the reaction can be performed in ethanol as the solvent. A one-pot cascade reaction could be established commencing with the Ugi-reaction to ensure diversity.

Enzymatic resolution of alicyclic 1,3-amino alcohols in organic media

Abstract Racemic cis - and trans -2-aminocyclohexane-1-methanol and cis - and trans -2-amino-4-cyclohexene-1-methanol were resolved via lipase-catalysed O -acylation of their Z derivatives, using vinyl butyrate in different ether solvents. In accordance with the empirical rule, most of the screened lipases preferred the 1 S enantiomer.

Atomic Layer Deposition of Pt Nanoparticles within the Cages of MIL-101: A Mild and Recyclable Hydrogenation Catalyst

We present the in situ synthesis of Pt nanoparticles within MIL-101-Cr (MIL = Materials Institute Lavoisier) by means of atomic layer deposition (ALD). The obtained Pt@MIL-101 materials were characterized by means of N2 adsorption and X-ray powder diffraction (XRPD) measurements, showing that the structure of the metal organic framework was well preserved during the ALD deposition. X-ray fluorescence (XRF) and transmission electron microscopy (TEM) analysis confirmed the deposition of highly dispersed Pt nanoparticles with sizes determined by the MIL-101-Cr pore sizes and with an increased Pt loading for an increasing number of ALD cycles. The Pt@MIL-101 material was examined as catalyst in the hydrogenation of different linear and cyclic olefins at room temperature, showing full conversion for each substrate. Moreover, even under solvent free conditions, full conversion of the substrate was observed. A high concentration test has been performed showing that the Pt@MIL-101 is stable for a long reaction time without loss of activity, crystallinity and with very low Pt leaching.