Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    Deconjugation of soy isoflavone glucuronides needed for estrogenic activity
    Islam, M.A. ; Bekele, R. ; Berg, J.H.J. van den; Kuswanti, Y. ; Thapa, O. ; Soltani, S. ; Leeuwen, F.X.R. ; Rietjens, I.M.C.M. ; Murk, A.J. - \ 2015
    Toxicology in Vitro 29 (2015)4. - ISSN 0887-2333 - p. 706 - 715.
    beta-messenger-rna - in-vitro - er-beta - receptor-beta - cell-proliferation - human plasma - cancer - expression - alpha - genistein
    Soy isoflavones (SIF) are present in the systemic circulation as conjugated forms of which the estrogenic potency is not yet clear. The present study provides evidence that the major SIF glucuronide metabolites in blood, genistein-7-O-glucuronide (GG) and daidzein-7-O-glucuronide (DG), only become estrogenic after deconjugation. The estrogenic potencies of genistein (Ge), daidzein (Da), GG and DG were determined using stably transfected U2OS-ERa, U2OS-ERß reporter gene cells and proliferation was tested in T47D-ERß cells mimicking the ERa/ERß ratio of healthy breast cells and inT47D breast cancer cells. In all assays applied, the estrogenic potency of the aglycones was significantly higher than that of their corresponding glucuronides. UPLC analysis revealed that in U2OS and T47D cells, 0.2-1.6% of the glucuronides were deconjugated to their corresponding aglycones. The resulting aglycone concentrations can account for the estrogenicity observed upon glucuronide exposure. Interestingly, under similar experimental conditions, rat breast tissue S9 fraction was about 30 times more potent in deconjugating these glucuronides than human breast tissue S9 fraction. Our study confirms that SIF glucuronides are not estrogenic as such, and that the small % of deconjugation in the cell is enough to explain the slight bioactivity observed for the SIF-glucuronides. Species differences in deconjugation capacity should be taken into account when basing risk-benefit assessment of these SIF for the human population on animal data.
    Polyfluorinated substances in abiotic standard reference materials
    Reiner, J.L. ; Blaine, A.C. ; Higgins, C.P. ; Kwadijk, C.J.A.F. - \ 2015
    Analytical and Bioanalytical Chemistry 407 (2015)11. - ISSN 1618-2642 - p. 2975 - 2983.
    alkyl acid concentrations - perfluorinated compounds - temporal trends - perfluorooctane sulfonate - spatial trends - human plasma - house-dust - perfluorochemicals - contaminants - china
    The National Institute of Standards and Technology (NIST) has a wide range of Standard Reference Materials (SRMs) which have values assigned for legacy organic pollutants and toxic elements. Existing SRMs serve as homogenous materials that can be used for method development, method validation, and measurement for contaminants that are now of concern. NIST and multiple groups have been measuring the mass fraction of a group of emerging contaminants, polyfluorinated substances (PFASs), in a variety of SRMs. Here we report levels determined in an interlaboratory comparison of up to 23 PFASs determined in five SRMs: sediment (SRMs 1941b and 1944), house dust (SRM 2585), soil (SRM 2586), and sludge (SRM 2781). Measurements presented show an array of PFASs, with perfluorooctane sulfonate being the most frequently detected. SRMs 1941b, 1944, and 2586 had relatively low concentrations of most PFASs measured while 23 PFASs were at detectable levels in SRM 2585 and most of the PFASs measured were at detectable levels in SRM 2781. The measurements made in this study were used to add values to the Certificates of Analysis for SRMs 2585 and 2781.
    Conversion of major soy isoflavone glucosides and aglycones in in vitro intestinal models
    Islam, M.A. ; Punt, A. ; Spenkelink, A. ; Murk, A.J. ; Leeuwen, F.X.R. ; Rietjens, I. - \ 2014
    Molecular Nutrition & Food Research 58 (2014)3. - ISSN 1613-4125 - p. 503 - 515.
    rat small-intestine - lactase-phlorhizin hydrolase - caco-2 cell monolayers - beta-glucosidase - 1st-pass metabolism - phyto-estrogens - human plasma - absorption - bioavailability - glycosides
    ScopeThis study compares conversion of three major soy isoflavone glucosides and their aglycones in a series of in vitro intestinal models. Methods and resultsIn an in vitro human digestion model isoflavone glucosides were not deconjugated, whereas studies in a Caco-2 transwell model confirmed that deconjugation is essential to facilitate transport across the intestinal barrier. Deconjugation was shown upon incubation of the isoflavone glucosides with rat as well as human intestinal S9. In incubations with rat intestinal S9 lactase phlorizin hydrolase, glucocerebrosidase, and cytosolic broad-specific -glucosidase all contribute significantly to deconjugation, whereas in incubations with human intestinal S9 deconjugation appeared to occur mainly through the activity of broad-specific -glucosidase. Species differences in glucuronidation and sulfation were limited and generally within an order of magnitude with 7-O-glucuronides being the major metabolites for all three isoflavone aglycones and the glucuronidation during first pass metabolism being more efficient in rats than in humans. Comparison of the catalytic efficiencies reveals that deconjugation is less efficient than conjugation confirming that aglycones are unlikely to enter the systemic circulation. ConclusionAltogether, the data point at possible differences in the characteristics for intestinal conversion of the major soy isoflavones between rat and human, especially with respect to their deconjugation.
    In Silico Prediction and Automatic LC–MSn Annotation of Green Tea Metabolites in Urine
    Ridder, L.O. ; Hooft, J.J.J. van der; Verhoeven, S. ; Vos, R.C.H. de; Vervoort, J.J.M. ; Bino, R.J. - \ 2014
    Analytical Chemistry 86 (2014)10. - ISSN 0003-2700 - p. 4767 - 4774.
    human fecal microbiota - mass-spectrometry - structural elucidation - human plasma - phenolic-compounds - spectral trees - polyphenols - identification - absorption - metabolomics
    The colonic breakdown and human biotransformation of small molecules present in food can give rise to a large variety of potentially bioactive metabolites in the human body. However, the absence of reference data for many of these components limits their identification in complex biological samples, such as plasma and urine. We present an in silico workflow for automatic chemical annotation of metabolite profiling data from liquid chromatography coupled with multistage accurate mass spectrometry (LC-MSn), which we used to systematically screen for the presence of tea-derived metabolites in human urine samples after green tea consumption. Reaction rules for intestinal degradation and human biotransformation were systematically applied to chemical structures of 75 green tea components, resulting in a virtual library of 27¿245 potential metabolites. All matching precursor ions in the urine LC–MSn data sets, as well as the corresponding fragment ions, were automatically annotated by in silico generated (sub)structures. The results were evaluated based on 74 previously identified urinary metabolites and lead to the putative identification of 26 additional green tea-derived metabolites. A total of 77% of all annotated metabolites were not present in the Pubchem database, demonstrating the benefit of in silico metabolite prediction for the automatic annotation of yet unknown metabolites in LC–MSn data from nutritional metabolite profiling experiments.
    Population-based nutrikinetic modelling of phytochemical exposure
    Velzen, E.J.J. van; Westerhuis, J.A. ; Grün, C.H. ; Duynhoven, J.P.M. van; Jacobs, D.M. ; Eilers, P.H.C. ; Mulder, T.P. ; Foltz, M. ; Garczarek, U. ; Kemperman, R. ; Vaughan, E.E. ; Smilde, A.K. - \ 2014
    Metabolomics 10 (2014)6. - ISSN 1573-3882 - p. 1059 - 1073.
    red wine/grape juice - black tea - dietary polyphenols - phenolic metabolites - nutrition research - food sources - human plasma - green tea - gut model - pharmacokinetics
    The beneficial health effects of fruits and vegetables have been attributed to their polyphenol content. These compounds undergo many bioconversions in the body. Modeling polyphenol exposure of humans upon intake is a prerequisite for understanding the modulating effect of the food matrix and the colonic microbiome. This modeling is not a trivial task and requires a careful integration of measuring techniques, modeling methods and experimental design. Moreover, both at the population level as well as the individual level polyphenol exposure has to be quantified and assessed. We developed a strategy to quantify polyphenol exposure based on the concept of nutrikinetics in combination with population-based modeling. The key idea of the strategy is to derive nutrikinetic model parameters that summarize all information of the polyphenol exposure at both individual and population level. This is illustrated by a placebo-controlled crossover study in which an extract of wine/grapes and black tea solids was administered to twenty subjects. We show that urinary and plasma nutrikinetic time-response curves can be used for phenotyping the gut microbial bioconversion capacity of individuals. Each individual harbours an intrinsic microbiota composition converting similar polyphenols from both test products in the same manner and stable over time. We demonstrate that this is a novel approach for associating the production of two gut-mediated ¿-valerolactones to specific gut phylotypes. The large inter-individual variation in nutrikinetics and ¿-valerolactones production indicated that gut microbial metabolism is an essential factor in polyphenol exposure and related potential health benefits
    Measurement of palmitoylethanolamide and other N-acylethanolamines during physiological and pathological conditions
    Balvers, M.G.J. ; Verhoeckx, K.C.M. ; Meijerink, J. ; Wortelboer, H.M. ; Witkamp, R.F. - \ 2013
    CNS & Neurological Disorders 12 (2013)1. - ISSN 1871-5273 - p. 26 - 33.
    tandem mass-spectrometry - polyunsaturated fatty-acids - human plasma - adipose-tissue - endocannabinoid metabolome - electrospray-ionization - palmitoyl-ethanolamine - quantitative method - rat-brain - fish-oil
    Palmitoylethanolamide (PEA) belongs to the N-acyl ethanolamines (NAEs), a group of endogenous compounds involved in a variety of physiological processes, including energy homeostasis and inflammation. This review focuses on the analysis of PEA in plasma and tissues and discusses effects of diet and some pathological processes on PEA levels. Originally isolated from egg yolk, PEA has been detected in a variety of tissues and plasma of different species. The compound is present at relatively high levels compared to other NAEs and now mostly analysed using liquid chromatography coupled to mass spectrometry. PEA plasma concentrations show marked fluctuations during the day. However, concentrations in tissues are likely to be more relevant than those in plasma. Most studies suggest that compared to other NAEs, tissue PEA tissue levels are not influenced by changes in dietary fatty acid composition. Effects of inflammation and disease on PEA tissue levels show differences between different models and studies. Therefore, more research is needed on the endogenous role and tissue kinetics of PEA during disease. The rediscovery of the therapeutic potential of PEA has fuelled research and the development of new pharmaceutical formulations. With regard to this there is a need for better kinetic data and models, preferably also on its tissue disposition. Moreover, it is important to learn more about effects of exogenous PEA on the kinetics of other NAEs (and endocannabinoids) and effects of inhibiting its breakdown using inhibitors of the degrading enzymes fatty acid amide hydrolase or N-acylethanolamine-hydrolyzing acid amidase.
    Quantitative Profiling of Oxylipins through Comprehensive LC-MS/MS Analysis: Application in cardiac surgery
    Strassburg, K. ; Huijbrechts, A.M.L. ; Kortekaas, K. ; Lindeman, J. ; Pedersen, T.L. ; Newman, J.W. ; Dane, A. ; Berger, R. ; Brenkman, A. ; Hankemeier, T. ; Duynhoven, J.P.M. van; Kalkhoven, E. ; Vreeken, R. - \ 2012
    Analytical and Bioanalytical Chemistry 404 (2012)5. - ISSN 1618-2642 - p. 1413 - 1426.
    tandem mass-spectrometry - soluble epoxide hydrolase - arachidonic-acid - human plasma - lipidomic analysis - fatty-acids - in-vivo - dihydroxyeicosatrienoic acids - hydroxyeicosatetraenoic acids - simultaneous quantification
    Oxylipins, including eicosanoids, affect a broad range of biological processes, such as the initiation and resolution of inflammation. These compounds, also referred to as lipid mediators, are (non-) enzymatically generated by oxidation of polyunsaturated fatty acids such as arachidonic acid (AA). A plethora of lipid mediators exist which makes the development of generic analytical methods challenging. Here we developed a robust and sensitive targeted analysis platform for oxylipins and applied it in a biological setting, using high performance liquid chromatography coupled to tandem mass spectrometry (HPLC-MS/MS) operated in dynamic multiple reaction monitoring (dMRM). Besides the well-described AA metabolites, oxylipins derived from linoleic acid, dihomo-¿-linolenic acid, a-linolenic acid, eicosapentaenoic acid and docosahexaenoic acid were included. Our comprehensive platform allows the quantitative evaluation of approximately 100 oxylipins down to low nanomolar levels. Applicability of the analytical platform was demonstrated by analyzing plasma samples of patients undergoing cardiac surgery. Altered levels of some of the oxylipins, especially in certain monohydroxy fatty acids such as 12-HETE and 12-HEPE, were observed in samples collected before and 24 h after cardiac surgery. These findings indicate that this generic oxylipin profiling platform can be applied broadly to study these highly bioactive compounds in relation to human disease.
    A simple and rapid extraction method for sensitive deterimination of perfluoroalkyl substances in blood serum suitable for exposure evaluation
    Luque, N. ; Ballesteros-Gomez, A. ; Leeuwen, S.P.J. van - \ 2012
    Journal of Chromatography. A, Including electrophoresis and other separation methods 1235 (2012). - ISSN 0021-9673 - p. 84 - 91.
    tandem mass-spectrometry - organic-compounds prior - solid-phase extraction - liquid-chromatography - perfluorinated compounds - supramolecular solvents - coacervative microextraction - polyfluoroalkyl substances - perfluorooctane sulfonate - human plasma
    In this work, we propose a microextraction method based on a new supramolecular solvent (SUPRAS) made up of reverse aggregates of hexanoic acid, combined with liquid chromatography/triple quadrupole mass spectrometry (LC/QQQ MS-MS) for the determination of the perfluoroalkyl substances (PFASs) in blood serum. A SUPRAS is a nano-structured liquid made up of surfactant aggregates synthesized through a self-assembly process. The method involved the acidification of 765µL of blood serum (600µmol of hydrochloric acid per mL of serum) followed by the addition of hexanoic acid (97µL) and tetrahydrofuran (THF) (600µL), conditions under which the supramolecular solvent (~360µL) formed in situ after vortex-shaking and centrifugation. Parameters affecting extraction efficiency and concentration factors were studied. The overall sample treatment took only 20min and several samples (20-30) can be simultaneously analyzed using conventional lab equipments, making additional investments unnecessary. Recoveries for the internal standards in samples ranged from 75 to 89% with relative standard deviations between 1 and 15%. Calibration was based on the use of internal standards. The method was very sensitive with detection limits ranging from 2 to 20pgmL(-1) for PFASs. The approach developed was successfully applied to the determination of PFASs in different blood serum samples. The concentration of PFASs found in samples of animal origin ranged between 17 and 197.3pgmL(-1) and between 84 and 5168pgmL(-1) in samples of human origin. Both the analytical and operational features of this method make it suitable for the evaluation of exposure to PFASs.
    Determination of perfluorinated alkyl acid concnetrations in biological standard reference materials
    Reiner, J.L. ; O'Connell, S.G. ; Butt, C.M. ; Kwadijk, C.J.A.F. - \ 2012
    Analytical and Bioanalytical Chemistry 404 (2012)9. - ISSN 1618-2642 - p. 2683 - 2692.
    marine food-web - perfluoroalkyl contaminants - perfluorooctane sulfonate - human plasma - great-lakes - water - samples - serum - environment - matrices
    Standard reference materials (SRMs) are homogeneous, well-characterized materials used to validate measurements and improve the quality of analytical data. The National Institute of Standards and Technology (NIST) has a wide range of SRMs that have mass fraction values assigned for legacy pollutants. These SRMs can also serve as test materials for method development, method validation, and measurement for contaminants of emerging concern. Because inter-laboratory comparison studies have revealed substantial variability of measurements of perfluoroalkyl acids (PFAAs), future analytical measurements will benefit from determination of consensus values for PFAAs in SRMs to provide a means to demonstrate method-specific performance. To that end, NIST, in collaboration with other groups, has been measuring concentrations of PFAAs in a variety of SRMs. Here we report levels of PFAAs and perfluorooctane sulfonamide (PFOSA) determined in four biological SRMs: fish tissue (SRM 1946 Lake Superior Fish Tissue, SRM 1947 Lake Michigan Fish Tissue), bovine liver (SRM 1577c), and mussel tissue (SRM 2974a). We also report concentrations for three in-house quality-control materials: beluga whale liver, pygmy sperm whale liver, and white-sided dolphin liver. Measurements in SRMs show an array of PFAAs, with perfluorooctane sulfonate (PFOS) being the most frequently detected. Reference and information values are reported for PFAAs measured in these biological SRMs.
    Quantitative trace analysis of a broad range of antiviral drugs in poultry muscle using column-switch liquid chromatography coupled to tandem mass spectrometry
    Berendsen, B.J.A. ; Wegh, R.S. ; Essers, M.L. ; Stolker, A.A.M. ; Weigel, S. - \ 2012
    Analytical and Bioanalytical Chemistry 402 (2012)4. - ISSN 1618-2642 - p. 1611 - 1623.
    metabolite oseltamivir carboxylate - solid-phase extraction - influenza-a virus - lc-ms/ms method - human plasma - rat plasma - human serum - resistance - amantadine - ribavirin
    A liquid chromatography–tandem mass spectrometry method for the analysis of seven antiviral drugs, zanamivir, ribavirin, oseltamivir, oseltamivir carboxylate, amantadine, rimantadine and arbidol, in poultry muscle is reported. The antiviral drugs were extracted from the homogenized poultry muscle sample using methanol. The extract was purified using tandem solid-phase extraction combining a cation exchange cartridge and a phenylboronic acid cartridge. To prevent excessive matrix effects, the analytes were separated from the matrix constituents using a column-switch liquid chromatography system combining a reversed-phase and a Hypercarb analytical column. Detection was carried out using tandem mass spectrometry. The method was fully validated according to 2002/657/EC [1] and proved to be adequate for quantification and confirmation of zanamivir and ribavirin at 10 µg kg-1, oseltamivir, oseltamivir carboxylate, amantadine and rimantadine at levels below 1.0 µg kg-1 and for qualitative confirmatory analysis of arbidol at levels below 1 µg kg-1.
    Quantitative trace analysis of eight chloramphenicol isomers in urine by chiral liquid chromatography coupled to tandem mass spectrometry
    Berendsen, B.J.A. ; Essers, M.L. ; Stolker, A.A.M. ; Nielen, M.W.F. - \ 2011
    Journal of Chromatography. A, Including electrophoresis and other separation methods 1218 (2011)41. - ISSN 0021-9673 - p. 7331 - 7340.
    human plasma - antibiotic chloramphenicol - enantiomeric separation - residues - meat - dextramycin - 2002/657/ec - validation - seafood - drugs
    Chloramphenicol is a broad-spectrum antibiotic with, apart from its human medicinal use, veterinary abuse in all major food-producing animals. Chloramphenicol occurs in four stereoisomers (all para-nitro substituted) and furthermore four meta-nitro analogs of chloramphenicol exist. In this paper these are referred to as eight chloramphenicol isomers. According to EU regulations an analytical method should be able to discriminate the analyte from interfering substances that might be present in the sample, including isomers. For the first time a quantitative method for the analysis of trace levels of eight chloramphenicol isomers in urine by chiral liquid chromatography in combination with tandem mass spectrometric detection is reported. The separation of the isomers on the analytical column, the clean-up of urine and the selectivity of the monitored product ions turned out to be critical parameters. To obtain reproducible retention isocratic elution on a chiral AGP column was applied. For urine samples matrix compounds present in the final extract caused decreased retention of the isomers on the chiral stationary phase and a lack of chromatographic resolution. Therefore an extended clean-up procedure that combines solid phase extraction and liquid–liquid extraction had to be developed. The final method was fully validated and showed satisfactory performance for all isomers with decision limits (CCa) ranging from 0.005 to 0.03 µg L-1 and within-laboratory reproducibility of all isomers below 20% at the minimum required performance limit level of 0.3 µg L-1. --------------------------------------------------------------------------------
    Human NAD(P)H:Quinone oxidoreductase inhibition by flavonoids in living cells
    Lee, Y.Y. ; Westphal, A.H. ; Haan, L.H.J. de; Aarts, J.M.M.J.G. ; Rietjens, I.M.C.M. - \ 2005
    Free Radical Biology and Medicine 39 (2005)2. - ISSN 0891-5849 - p. 257 - 265.
    hamster ovary cells - dt-diaphorase - quinone oxidoreductase - acceptor oxidoreductase - antitumor quinones - human plasma - cancer risk - quercetin - reductase - rat
    Procedures for assessing enzyme inhibition in living cells are an important tool in the study of the relevance of enzyme-catalyzed reactions and interactions in the human body. This paper presents the effects of flavonoids on NAD(P)H:quinone oxidoreductase 1 (NQO1) activity, by a newly developed method to measure NQO1 inhibition in intact cells. The principle of this method is based on the resorufin reductase activity of NQO1. The change in fluorescence in time was used to determine NQO1 activity in intact Chinese hamster ovary (CHO) cells genetically engineered to overexpress human NQO1. Applying this method to determine the inhibitory effects of reported in vitro NQO1 inhibitors (dicoumarol, 7,8-dihydroxyflavone, chrysin) showed that for all inhibitors tested, the IC50 in intact cells was at least 3 orders of magnitude higher than the IC50 in cell lysates. This result demonstrates that in vitro studies with purified NQO1 or with extracts from disrupted tissues are of limited value for obtaining insight into the situation in living cells. Possible factors underlying this discrepancy are being discussed. For the first time, we determined NQO1 inhibition by flavonoids in cells without disruption of the cells or addition of cofactors, enabling the assessment of enzymatic activity and the interaction of modulators of enzymatic activity in an intracellular situation.
    Absorption, bioavailability and metabolism of flavonoids
    Hollman, P.C.H. - \ 2004
    Pharmaceutical biology 42 (2004)suppl.. - ISSN 1388-0209 - p. 74 - 83.
    lactase-phlorhizin hydrolase - human plasma - red wine - quercetin glycosides - cocoa procyanidins - urinary-excretion - mass-spectrometry - black tea - green tea - humans
    To unravel mechanisms of action of dietary flavonoids in their potential role in disease prevention, it is crucial to know the factors that determine their release from foods, their extent of absorption, and their fate in the organism. Research on absorption, metabolism, and bioavailability of flavonoids will answer these questions. The subclass, flavonols, with quercetin as the major dietary flavonol, was the first to be studied, and information on other subclasses of flavonoids is emerging. Most flavonoids, except for the subclass of catechins, are present in plants bound to sugars as ß-glycosides. This structural feature determines whether the flavonoid can be absorbed from the small intestine or has to go to the colon before absorption can occur. Generally, but exceptions have been described, glucosides are the only glycosides that can be absorbed from the small intestine. Absorption from the small intestine is more efficient than from the colon and will lead to higher plasma values. After absorption from the small intestine, flavonoids are conjugated with glucuronic acid or sulfate or O-methylation may occur. The conjugation reactions, which occur in the small intestine upon absorption, are very efficient. As a result, no free flavonoid aglycones can be found in plasma or urine, except for catechins. Plasma concentrations due to a normal diet will be less than 1 µM. Flavonoids that cannot be absorbed from the small intestine, and absorbed flavonoids secreted with bile, will be degraded in the colon by microorganisms, which will break down the flavonoid ring structure. The resulting phenolic acids have partly been characterised. These phenolic acids can be absorbed and have been measured in plasma and urine. Future research will need to address tissue distribution, cellular uptake, and cellular metabolism
    Intestinal uptake of genistein and its glycoside in the rat using various isolated perfused gut segments
    Steensma, A. ; Ploum, M.E. ; Noteborn, H.P.J.M. - \ 2004
    Environmental Toxicology and Pharmacology 17 (2004)2. - ISSN 1382-6689 - p. 103 - 110.
    epithelial caco-2 cells - human plasma - quercetin - glucosides - bioavailability - absorption - women - quercetin-3-glucoside - isoflavones - transport
    Genistein receives much attention because of its potential to prevent hormone-related cancer and cardiovascular diseases. Limited information is available on the pharmacokinetics of this compound like, for instance, their intestinal uptake by humans and systematic bioavailability. In this study, the fate of the absorption of genistein and its glycoside has been analysed in various isolated perfused gut segments of the rat. In all perfused gut segments the transport of genistein was higher compared to its glycoside. Furthermore, it appeared that the resorbate (i.e. serosal side) concentration of genistein was the highest in ileac segments, whereas the transport of genistein in the various other segments tested showed no difference between intestinal compartments. Less than 0.2 f genistin appeared in the resorbate fluid of all isolated gut segments. The main site of metabolism of genistein and its glycoside appears to be located in the jejunal compartment of the rat gut. About 38 f genistein and about 29 f genistin metabolised within 2 h of perfusion. In the ileac and colonic intestinal segments, genistein metabolised for only 10&Eth;For the first time, this study demonstrated that genistin could be metabolised by epithelial cells present in isolated colonic segments. However, the metabolites of genistin did not occur at the serosal side (the resorbate) of isolated colonic segments. We assume that there is no absorption of genistin and/or its metabolites in or through colonic tissue of the rat.
    Activation of the Ah receptor by extracts of dietary herbal supplements, vegetables, and fruits
    Jeuken, A. ; Keser, B.J.G. ; Khan, E. ; Brouwer, A. ; Koeman, J.H. ; Denison, M.S. - \ 2003
    Journal of Agricultural and Food Chemistry 51 (2003)18. - ISSN 0021-8561 - p. 5478 - 5487.
    aryl-hydrocarbon receptor - drug-metabolizing-enzymes - x-associated protein-2 - signal-transduction - transcriptional enhancer - tea catechins - human plasma - rat-liver - in-vitro - dioxin
    The aryl hydrocarbon receptor (AhR) is a ligand-dependent transcription factor that can be activated by a structurally diverse range of synthetic and natural chemicals, and it mediates the toxic and biological effects of environmental contaminants such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). The spectrum of chemicals that bind to and activate the AhR signal transduction pathway and the identity of materials containing AhR active chemicals is only now being defined. Utilizing AhR-dependent gel retardation and reporter gene bioassays, the screening of extracts of 22 dietary herbal supplements and 21 food products (vegetables and fruits) was performed to identify those containing AhR agonists. Several herbal extracts (ginseng, Fo-Ti, white oak bark, licorice, ginkgo biloba, and black cohosh) stimulated AhR DNA binding and gene expression to levels between 20 and 60% of that produced by TCDD. Although some food extracts (corn, jalapeño pepper, green bell pepper, apple, Brussels sprout, and potato) were relatively potent activators of AhR DNA binding (30-50% of TCDD), only corn and jalapeño pepper extracts induced AhR-dependent luciferase reporter gene expression. However, dilution of corn, jalapeño pepper, bell pepper, and potato extracts dramatically increased their ability to induce luciferase activity, suggesting that these extracts contained AhR antagonists whose effectiveness was overcome by dilution. Overall, these results demonstrate that dietary products can be a major source of naturally occurring AhR ligands to which animals and humans are chronically exposed.
    Chlorogenic acid, quercetin-3-rutinoside and black tea phenols are extensively metabolized in humans
    Olthof, M.R. ; Hollman, P.C.H. ; Buijsman, M.N.C.P. ; Amelsvoort, J.M.M. van; Katan, M.B. - \ 2003
    The Journal of Nutrition 133 (2003)6. - ISSN 0022-3166 - p. 1806 - 1814.
    potentially anticarcinogenic flavonoids - caffeic acid - human plasma - derivatives - quercetin - bioavailability - consumption - microflora - catechins - lithium
    Dietary phenols are antioxidants, and their consumption might contribute to the prevention of cardiovascular disease. Coffee and tea are major dietary sources of phenols. Dietary phenols are metabolized extensively in the body. Lack of quantitative data on their metabolites hinders a proper evaluation of the potential biological effects of dietary phenols in vivo. The aim of this study was to identify and quantify the phenolic acid metabolites of chlorogenic acid (major phenol in coffee), quercetin-3-rutinoside (major flavonol in tea) and black tea phenols in humans, and determine the site, of metabolism. Healthy humans (n = 20) with an intact colon participated in a dietary controlled crossover study, and we identified and quantified similar to60 potential phenolic acid metabolites in urine. Half of the ingested chlorogenic acid and 43% of the tea phenols were metabolized to hippuric acid. Quercetin-3-rutinoside was metabolized mainly to phenylacetic acids, i.e., 3-hydroxyphenylacetic acid (36%), 3-methoxy-4-hydroxyphenylacetic acid (8%) and 3,4-dihydroxyphenylacetic acid (5%). In contrast, in seven humans without a colon, we found only traces of phenolic acid metabolites in urine after they had ingested chlorogenic acid and quercetin-3-rutinoside. This implies that the colonic microflora convert most of these dietary phenols into metabolites that then reach the circulation. Metabolites of dietary phenols have lower antioxidant activity than their parent compounds; therefore, the contribution of dietary phenols to antioxidant activity in vivo might be lower than expected from in vitro tests. J. Nutr. 133: 1806-1814, 2003.
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