C Manach

..These data should be considered in the design and interpretation of studies investigating the mechanisms and potential health effects of flavonoids...

..3'-O-Methylquercetin and conjugated derivatives of quercetin significantly prolonged the lag phase, but the magnitude of their effect was about half that of the aglycone...

..A thorough knowledge of the bioavailability of the hundreds of dietary polyphenols will help us to identify those that are most likely to exert protective health effects...

..Data are still too limited for assessment of hydroxycinnamic acids and other polyphenols. These data may be useful for the design and interpretation of intervention studies investigating the health effects of polyphenols...

..The length of human intervention studies should be increased, to more closely reflect the long-term dietary consumption of polyphenols...

..The aim of the present study was to determine the nature of the circulating metabolites, the plasma kinetics and the urinary excretion patterns of the flavanones, hesperidin and narirutin...

..Future research should focus on other procyanidin metabolites such as phenolic acids and on the effects of the unabsorbed oligomers and polymers on the human gastrointestinal tract...

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..05). Whatever the perfused compound, the efficiency of the absorption seemed to be linked to the intestinal conjugation process and to the luminal secretion of metabolites...

..The present work shows that a rapid quercetin absorption in the small intestine is very effective together with its active conjugation in intestinal cells...

..The total urinary excretion rate of phloretin was not affected by the forms administered, and was estimated to be 8.5 micromol/24 h in rats fed phloretin or phloridzin. Thus, 10.4% of the ingested dose was recovered in urine after 24 h...

..This result suggests that quercetin 3-O-beta-glucoside is hydrolysed before or during its intestinal absorption...

..The data further demonstrate the role of the rat small intestine in the glucuronidation and methylation of flavonoids as well as the role of the liver in sulfation, methylation and biliary excretion...

..Quercetin 3-glucose can be absorbed in the small intestine and is better absorbed than quercetin itself. By contrast, glycosides containing a rhamnose moiety could not be absorbed in the small intestine...

..Beyond clinical trials carried out with polyphenol-rich foods, more studies with pure polyphenols will also be needed to establish their role in the prevention of cardiovascular diseases...

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..More human studies are needed to provide clear evidence of their health protective effects and to better evaluate the risks possibly resulting from too high a polyphenol consumption...

..Levels of urinary excretion suggest that chlorogenic acid, gallic acid, epicatechin, naringenin or hesperetin could be used as specific biomarkers to evaluate the consumption of coffee, wine, tea or cocoa, and citrus juices respectively...

..In contrast to numerous flavonoids, absorbed phenolic acids are poorly excreted in the bile or gut lumen. Their bioavailability therefore appears to be governed largely by their uptake into the gut mucosa...

..No other metabolites could be detected by HPLC-electrospray ionization-MS-MS. These results show for the first time that chlorogenic acid is quickly absorbed in the rat stomach in its intact form...

..It has been applied to human urine samples collected from volunteers after consumption of different polyphenol-rich beverages in controlled conditions...

..Furthermore, anthocyanins are quickly metabolized and excreted into bile and urine as intact glycosides as well as methylated forms and glucuronidated derivatives...

..In conclusion, when flavonols are present in the diet as aglycons, they could be partly absorbed in the stomach, in contrast to their glycosidic forms which are not absorbed...

..Alternatively, some health effects of polyphenols may not require their absorption through the gut barrier. Their role as iron chelators in the gut lumen is briefly discussed...

..These results show that the formation of lignans from wheat bran is influenced by the diet, possibly because of an adaptation of the colonic microflora...

..More attention should be given in the future to these microbial metabolites and their biological properties to help explain the health effects of polyphenols that are not easily absorbed through the gut barrier...

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..1-10 micromol/L. For correct interpretation of results, future efforts to define biological activities of polyphenols must make use of the available data concerning bioavailability and metabolism in humans...

..Isoflavone mechanisms of action should thus be investigated in in vitro cell studies using physiological conditions, intracellular concentrations below 5 nmol/g and no intracellular deconjugation of the monoglucuronide metabolites...

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..Reproductive organs contained higher concentrations of isoflavones than heart, muscle, or thymus. Distribution of isoflavones in ewe tissues is unequal and may reflect specific impact in some target tissues...