Ein Beitrag zur Kenntnis der Flora der Dinarischen Alpen

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XXXVII.Ranunculus millefoliatus Vahl undR. garganicus Ten

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Bemerkungen über einige orientalische Pflanzenarten

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Asplenium lepidum Presl. in Ungarn

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Simultaneous analysis of ochratoxin A and its major metabolite ochratoxin alpha in plasma and urine for an advanced biomonitoring of the mycotoxin

Ochratoxin A (OTA) is a frequent mycotoxin contaminant found worldwide in foods and feedstuffs. Biomonitoring has been used to assess internal OTA exposure resulting from dietary intake and from other sources. Mycotoxin levels in blood and/or urine provide good estimates of past and recent exposure since OTA binds to serum proteins and is also partly excreted via the kidney. But, measuring OTA alone does not reflect its biotransformation. In light of scarce data on its metabolites in humans, it was the aim of this study to develop a method that allows analysis of OTA and its detoxication product ochratoxin alpha (OTα) in urine and in blood plasma. The method involves enzymatic hydrolysis of conjugates, liquid–liquid extraction, and analysis of sample extracts by liquid chromatography with fluorescence detection. Application of the validated method in a pilot study with 13 volunteers revealed the presence of OTA and OTα in all samples (limit of quantification: 0.05 ng/mL in urine, and 0.1 ng/mL in plasma). In line with negative findings of others, an OTA glucuronide was not detected, neither in urine nor in plasma. By contrast, conjugates of OTα (glucuronide and/or sulfate) are major products in these samples. This was confirmed by mass spectrometry detection. As OTα represents a large fraction of ingested mycotoxin, we propose to include analyses of this metabolite in future biomonitoring studies, also in light of the observed variations for urine OTα-levels that suggest different interindividual abilities for OTA-detoxification in humans.     

Ein Beitrag zur Kenntnis der Flora der Dinarischen Alpen

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Bemerkungen über einige orientalische Pflanzenarten XXIX

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Inhibition of prostaglandin H synthase–catalyzed cooxidation of diethylstilbestrol by α-naphthoflavone and β-naphthoflavone

Prostaglandin H synthase (PHS) has gained interest as a drugmetabolizing enzyme and has been shown to cooxidize and metabolically activate diethylstilbestrol (DES) in vitro. Both 7,8-benzoflavone (α-naphthoflavone, ANF) and 5,6-benzoflavone (β-naphthoflavone, BNF) have now been studied for their effects on PHS from ram seminal vesicle microsomes by means of several in vitro assays. The PHS-catalyzed cooxidation of DES, as measured by high-performance liquid chromatography (HPLC) analysis, is inhibited by BNF and ANF at micromolar concentrations, with median inhibitory concentrations (IC-50) of<20 and 40 μM, respectively. The oxidation of DES is inhibited whether it is initiated by arachidonic acid or by hydrogen peroxide, indicating that the benzoflavones inhibit PHS by a mechanism different from that of indomethacin. Monitoring of cyclooxygenase activity in an oxygraph also reveals an inhibition of PHS by BNF which depends only weakly on arachidonic acid concentration; inhibition by ANF is less pronounced under these conditions. Since PHS-catalyzed conversion of the benzoflavone compounds was detected under conditions permitting cooxidation, the inhibition of PHS by benzoflavones in vitro could either be a direct effect or possibly mediated via metabolites. Our data imply that ANF and BNF, in addition to their well-known role as modifiers of mixed-function oxidases, can affect the PHS-catalyzed metabolism of xenobiotics. This is discussed in the context of adverse effects caused by DES in vivo and in cell culture and must be taken into account when interpreting the modifying effect of benzoflavones on these endpoints.     

Bemerkungen über einige orientalische Pflanzenarten

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Bemerkungen über einige orientalische Pflanzenarten XXX

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