Flavonoids excretion

Healthy non-smokers, 6 males, 10 females Duplicate whole diet menus from organic or conventional sources, 22 day duration Significant increase in urinary flavonoid excretion for organic diet. No difference in antioxidant status between organic or conventional diets. (Grinder-Pedersen et al., 2003)... 

Catechol-O-methyltransferase (COMT EC 2.1.1.6) is located in many tissues and catalyzes the methylation of polyphenols. The methylation is a well-established pathway in the metabolism of flavonoids such as those that undergo 3, 4 -dihydrox-ylation of ring B excreted as 3 -0-methyl ether metabohtes in rat bile. " Recently, the apparent methylation of both cyanidin-3-glucoside and cyanidin-3-sambubioside (cyanidin is an anthocyanin with a 3, 4 -dihydroxylation of ring B) to peonidin-3-glucoside and peonidin-3-sambubioside was reported in humans. In rats, this transformation occurred mainly in the liver and was catalyzed by COMT."°... 

Grinder-Pedersen L, Rasmussen S E, Bugel S, Jorgensen L V, Dragsted L O, Gundersen V and Sandstrom B (2003), Effect of diets based on foods from conventional versus organic production on intake and excretion of flavonoids and markers of antioxidative defense in humans , J Agric. Food Chem, 51, 5671-5676. 

Major enzymes catalyzing flavonoid reactions are oxidative enzymes (i.e., polyphenoloxi-dases and peroxidases) arising from grape but also from molds contaminating them. Various hydrolytic enzymes (glycosidases, esterases), excreted by the fermentation yeasts or fungi or present in preparations added for technological purposes (e.g., pectinases), are also encountered in wine. 

Wollenweber, E., Mann, K., and Roitman, J.N, Flavonoid aglycones excreted by three Calceolaria species. Phytochemistry, 28, 2213, 1989. 

It seems that overall percentage of absorption, determined by measuring plasma levels of flavonols after enzymatic hydrolysis, does not exceed 2-3% of the ingested dose. It is also likely that, as with other micronutrients, the existence of a steady-state concentration of these compounds could result in diminished absorption. Thus, it is conceivable that the major parts of these flavonoids are either degraded to phenolic acids in the large intestine or excreted in the faeces [72]. 

Das NP. 1974. Studies on flavonoid metabolism. Excretion of m-hydroxyphenylhy-dracrylic acid from (plus)-catechin in the monkey (Macaca iris sp.). Drug Metab Dispos 2 209-213. 

This biotransformation is common to many xenobiotics and diminishes the potential toxicity of the substrate and facilitates its biliary and urinary elimination by increasing its hydrophilicity. Flavonoid metabolites are transported to extrahe-patic tissues and eventually to the kidneys, where they are excreted in the urine or incorporated into bile and excreted in feces.13 Because phase II metabolism is highly efficient with respect to the flavonoids, aglycones (except for anthocyanins)... 

Figure 2.3 Absorption, metabolism, and excretion of flavonoids. Glucuronidation, methyla-tion, and sulfation are catalyzed by UDP-glucuronyltransferase, catechol-O-methyltrasferase, and sulfotransferase, respectively. Abbreviation LPH, lactase phlorizin hydrolase.

However, the effect of piperine on SULT and flavonoid status across the life cycle remains to be investigated. Induction of phase II metabolism appears to decrease the bioavailability and accelerate the excretion of flavonoids. For example, Siess et al.115 and Walle et al.116 reported flavones induced rat hepatic UGT activity in HepG2 and Caco-2 cells. This induction of UGT enhanced quercetin glucuronidation in Caco-2 cells. In addition to inducing UGT activity, the flavone chrysin inhibits hepatic SULT-mediated sulfation of acetaminophen and minoxidol." The impact of chrysin on the capacity of COMT action toward flavonoids has not been examined. Further, the effect of age on phase II modulation by piperine and chrysin has not been reported. Thus, information on the relationship between age and intake of flavonoids and other phytochemicals that also affect phase II metabolism is required. 

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