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Articles

Catechin Is Metabolized by Both the Small Intestine and Liver of Rats

Laboratoire des Maladies Métaboliques et Micronutriments, INRA, 63122 Saint-Genès Champanelle, France

¹To whom correspondence and reprint requests should be addressed. E-mail: cmorand{at}clermont.inra.fr.

	ABSTRACT

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
Flavan-3-ols are the most abundant flavonoids in the human diet, but little is known about their absorption and metabolism. In this study, the absorption and metabolism of the monomeric flavan-3-ol, catechin, was investigated after the in situ perfusion of the jejunum + ileum in rats. Five concentrations of catechin were studied, ranging from 1 to 100 µmol/L. The absorption of catechin was directly proportional to the concentration, and 35 ± 2% of the perfused catechin was absorbed during the 30-min period. Effluent samples contained only native catechin, indicating that intestinal excretion of metabolites is not a mechanism of catechin elimination. Catechin was absorbed into intestinal cells and metabolized extensively because no native catechin could be detected in plasma from the mesenteric vein. Mesenteric plasma contained glucuronide conjugates of catechin and 3'-O-methyl catechin (3'OMC), indicating the intestinal origin of these conjugates. Additional methylation and sulfation occurred in the liver, and glucuronide + sulfate conjugates of 3'OMC were excreted extensively in bile. Circulating forms were mainly glucuronide conjugates of catechin and 3'OMC. 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.

KEY WORDS: • catechin • metabolism • absorption • rats • methylation

	INTRODUCTION

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
Flavan-3-ols are a class of flavonoids that are widely distributed in fruits and beverages including green tea, red wine, apples and chocolate (1 2 3 4) . In foods, they are present as monomers, oligomers and polymers; they may be esterified with gallic acid but are generally not present as glycosides (5) . Although their intake levels are not precisely known, they are likely the most abundant flavonoids in the human diet with estimates of consumption ranging from 0.1–0.5 g/d (6 ,7) . In addition to the widely reported in vitro biological activities of flavan-3-ols (8 ,9) , consumption of purified monomers and foods containing predominantly flavan-3-ols has been shown to reduce platelet activity, fatty streak development and certain cancers (6 ,10 11 12 13 14 15 16 17) . The particular mechanism(s) of action are impossible to establish without a complete understanding of their uptake as well as their metabolism and distribution among tissues and cells. The monomers catechin and epicatechin are absorbed and are present as glucuronidated, sulfated and methylated conjugates in human plasma (16 ,18 19 20 21) . However, it is unclear which tissues are responsible for their metabolism.

Until recently, the liver has been presumed to be responsible for most flavonoid metabolism due to its high concentrations of UDP-glucuronyltransferase (22 ,23) sulfotransferase (24 ,25) and catechol-O-methyltransferase (COMT)² (26) . However, conjugation enzyme activities are widely distributed among tissues (27) . In vitro studies indicate that the metabolism of epicatechin and other flavonoids can occur in the small intestine (28 29 30) . Studies with isolated rat intestine (31 32 33) also indicate that metabolism of several other flavonoids occurs with efficiency in the small intestine. The flavonol, quercetin, is extensively absorbed, metabolized and then reexcreted by the small intestine as was shown in an in situ perfusion model (34) .

In this study, the absorption and metabolism of catechin was investigated after in situ perfusion in the jejunum and ileum in rats. Like many intestinal perfusion models, the model allows the direct calculation of the amount absorbed as well as the characterization of metabolites formed by the intestine by their appearance in mesenteric blood. In contrast to models using isolated intestines, the in situ model can be used to study the metabolism and excretion at other sites such as the liver and can give insight into how the different organs function together in the living animal. Thus, the aim of the present work was to investigate the absorption and metabolism of catechin by the small intestine as well as the subsequent contribution of the liver in metabolism and excretion.

	MATERIALS AND METHODS

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
Chemicals and reagents.

(+)-Catechin, and (+)-taxifolin were purchased from Extrasynthese (Genay, France). The 3'- and 4'-O-methylated conjugates of catechin were synthesized using a mixture of 250 mg (+)-catechin, 500 mg K₂CO₃ and 1 mL methyl iodide in 20 mL acetone, which was placed in an ultrasonic bath for 2.5 h. The 3'- and 4'-O-methylated conjugates were purified by semipreparative HPLC and the positions of the methyl groups were confirmed by one-dimensional (1D)-difference nuclear Overhauser effect spectroscopy as previously described (35) . ß-Glucuronidase (G-0376; EC 3.2.1.31), arylsulfatase (S-9626; EC 3.1.6.1) and saccharic acid 1,4-lactone were purchased from Sigma Chemical (St. Louis, MO).

Animals and sample collection.

Male Wistar rats (n = 20), weighing 180–200 g, were housed in temperature-controlled rooms (22°C), with a dark period from 0800 to 2000 h and access to the semipurified diet from 0800 to 1600 h. The rats were fed a standard semipurified diet containing 730 g/kg wheat starch, 150 g/kg casein, 60 g/kg mineral mixture, 10 g/kg vitamin mixture and 50 g/kg corn oil for 2 wk before the experiment as previously described (36) . The rats were maintained and handled according to the recommendations of the Institutional Ethics Committee, in accordance with the decree no. 87–848.

The rats were deprived of food for 18 h, anesthetized with sodium pentobarbital (40 mg/kg body) and kept alive throughout the perfusion period. An incision of the peritoneal cavity was performed, the bile duct was cannulated and cannulas were installed at the extremities of the jejunum and ileum (5 cm distal from the duodeno-jejuno junction to the ileocecal valve). The cannulated segment was perfused continuously in situ for 30 min at 1 mL/min with a buffer containing 2.5 mmol/L KH₂PO₄, 2.5 mmol/L K₂HPO₄, 5.0 mmol/L NaHCO₃, 50 mmol/L NaCl, 50 mmol/L KCl, 2 mmol/L CaCl₂, 2 mmol/L MgCl₂, 8.0 mmol/L glucose, 2 mmol/L glutamine and 1.0 mmol/L taurocholic acid at pH 6.7. The buffer was supplemented with 1, 5, 15, 30 or 100 µmol/L catechin to provide total doses of 0.15–15 µmol/kg. Aliquots were collected directly at the exit of the ileum during the last 5 min of perfusion. All volumes were recorded and concentrations were corrected for intestinal absorption of water. Absorption was calculated as the difference in the amount perfused and the amount recovered in the effluent. Bile was collected from 0 to 20 min and from 20 to 30 min. At the end of the 30-min period, blood was drawn first from the mesenteric vein (0.5–1 mL) and then from the abdominal aorta (1–2 mL) into heparinized tubes. Plasma, bile and perfusate samples were acidified with 10 mL/L of 1 mol/L acetic acid and stored at -20°C.

Analysis of samples.

Plasma samples (50 µL) were spiked with 4 µmol/L taxifolin, the internal standard, and acidified with 6 µL of 0.58 mol/L acetic acid. Bile samples were diluted two- to fourfold in 0.1 mol/L sodium acetate (pH 4.9), and 50-µL samples were spiked with 4 µmol/L taxifolin. To determine the total amount of catechin and 3'-O-methyl catechin (3'OMC), plasma or bile was incubated for 15 min at 37°C after the addition of 1200 U of ß-glucuronidase and 25 U arylsulfatase dissolved in 10 µL sodium acetate buffer (100 mmol/L, pH 5.5). Individual conjugate forms of catechin in aortic and mesenteric plasma and bile were determined after perfusion with 30 and 100 µmol/L. Plasma and bile were incubated without enzymes (free, unconjugated catechin and 3'OMC), with 1200 U ß-glucuronidase (glucuronide conjugates) or 25 U arylsulfatase and 0.2 mol/L saccharic acid 1,4-lactone, an inhibitor of ß-glucuronidase (sulfate conjugates). Samples were extracted with 200 µL of 95% aqueous methanol containing 200 mmol/L HCl and centrifuged for 4 min at 14,000 x g. The resulting supernatant was analyzed as described below. Recoveries of catechin, 3'OMC and taxifolin from plasma and bile were >90% using this extraction procedure.

HPLC was performed using a Hypersil BDS 4.6 x 250 mm, 5-µm particle size analytical column (Life Sciences International, Cergy, France). Mobile phase A consisted of 3% acetonitrile in 30 mmol/L NaH₂PO₄ at pH 3.0, and mobile phase B consisted of 20% acetonitrile in 30 mmol/L NaH₂PO₄ at pH 3.0. The separation was performed at 35°C. The flow rate was 1 mL/min with a linear gradient from 0 to 50% B in 15 min and remaining at 50% B for 20 min. From 20 to 25 min, the gradient was increased to 100% B and then returned to 100% A for 40 min. Detection was performed with an 8-electrode CoulArray Model 5600 system (Eurosep, Cergy, France) with potentials set at 25, 100, 320, 400, 500,700, 800 and 900 mV. Concentrations of catechin and taxifolin were determined using the responses on the first two potentials and concentrations of 3'OMC were determined using the 3rd and 4th potentials.

Data analysis.

All numerical values are expressed as means ± SEM; significant differences were determined by ANOVA using Instat (San Diego, CA). Differences with P < 0.05 were considered significant.

	RESULTS

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Absorption of catechin.

Five different concentrations of catechin, ranging from 1 to 100 µmol/L, were perfused through the small intestine in situ. The absorption of catechin was directly proportional to the amount perfused (Fig. 1 ). The percentage absorbed (35 ± 2%) was not significantly different at any of the concentrations. Catechin in the effluent was present exclusively in its native form.

View larger version (12K): [in this window] [in a new window]   Figure 1. Absorption of catechin by the small intestine of rats after in situ perfusion of five concentrations of catechin for 30 min (total amount perfused in 30 mL = 0.03, 0.15, 0.45, 0.90 and 3.0 µmol). Values are means ± SEM, n = 4.

Plasma was taken from the mesenteric vein at the end of the 30-min perfusion period to determine the presence of metabolites that were formed in the small intestine. Levels of specific forms of catechin metabolites in mesenteric plasma, abdominal aortic plasma and bile after perfusion with 30 and 100 µmol/L are shown in Table 1 . Native catechin was not detected in untreated plasma taken from the mesenteric vein. Plasma taken from the mesenteric vein contained glucuronide conjugates of catechin and glucuronide conjugates of 3'OMC. No 4'-O-methylcatechin (4'OMC) or conjugates were detected. A chromatogram of plasma taken from the mesenteric vein after hydrolysis by ß-glucuronidase is shown in Figure 2 . The sum of the conjugate forms of catechin and 3'OMC in mesenteric plasma was proportional to the amount perfused and averaged 1.2 µmol/L after perfusion with 30 µmol/L catechin and 3.8 µmol/L after perfusion with 100 µmol/L catechin. The proportion of methylated metabolites tended to be higher (0.05 < P < 0.1) when perfusion was performed at 30 µmol/L than at 100 µmol/L.

View larger version (19K): [in this window] [in a new window]   Figure 2. Representative chromatogram of mesenteric plasma after in situ perfusion in the rat small intestine with 100 µmol/L catechin. Plasma was hydrolyzed by a ß-glucuronidase and extracted and analyzed by HPLC coupled to a multielectrode Coularray detection as described in materials and methods. Abbreviations: 3'OMC, 3'-O-methyl catechin; 4'OMC, 4'-O-methyl catechin.

Metabolites of catechin were eliminated extensively by bile. Bile flow was 238 ± 97 µL during the first 20 min of perfusion and 116 ± 28 µL during the last 10 min of perfusion. Specific conjugate forms were collected during the last 10 min of perfusion with 30 and 100 µmol/L in bile. The concentration of metabolites excreted in bile were 26.8 and 58.2 µmol/L after perfusion with 30 and100 µmol/L, respectively (Table 1) . The major metabolite present in bile was a glucuronidated + sulfated form of 3'OMC, but a glucuronide conjugate of 3'OMC was also present. No conjugates of 4'OMC were detected. Unmethylated forms of catechin were also excreted in bile, but at much lower concentrations (<0.1 µmol/L) (Table 1) .

Abdominal aortic plasma.

Plasma taken from the abdominal aortic artery contains the circulating metabolites that reach peripheral tissues. Aortic plasma contained total concentrations of catechin metabolites of 0.5 and 1.5 µmol/L after perfusion with 30 and 100 µmol/L catechin, respectively (Table 1) . Catechin and 3'OMC were both in glucuronidated form, although in some rats, very small but detectable quantities of the glucuronidated and sulfated forms of both catechin and 3'OMC were present. No 4'OMC or its conjugates could be detected. The proportion of methylated metabolites tended to be higher (0.05 < P < 0.1) when perfusion was performed at 30 µmol/L.

	DISCUSSION

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
We used an in situ model of intestinal perfusion to study the absorption and metabolism of catechin. The model allows the direct calculation of absorption by the small intestine. The animals are intact and alive throughout the experiment; thus, metabolism can occur in several different tissues. The model can distinguish between metabolic conjugation in the intestine as well as the liver and peripheral tissues by identifying metabolites in mesenteric plasma, bile and abdominal aortic plasma. The circulating metabolites after in situ perfusion are in agreement with those observed in rat feeding studies, namely, glucuronide conjugates of catechin and 3'OMC (37) although some sulfate conjugates have been reported (38) . Catechin in liver samples was extensively methylated (37) , which is consistent with our finding that the biliary metabolites were methylated. Shaw and Griffiths (39) reported that the major metabolite in bile was a glucuronidated form of 3'OMC; we report this metabolite as well as a form of 3'OMC that is both glucuronidated and sulfated. The agreement in metabolite composition with in vivo studies indicates that the metabolic processes that occur after in situ perfusion reflect the processes that occur after consumption of catechin by rats.

The effect of the catechin dose on absorption was investigated by perfusion at five different concentrations. A maximum concentration of 100 µmol/L catechin was chosen because the concentration could rarely be higher in the small intestine even after a concentrated food source of catechin (40) . The absorption of catechin was directly proportional to the concentration perfused, and this was reflected in metabolite levels in both mesenteric and aortic plasma. This finding is consistent with two studies that showed that plasma levels of epicatechin metabolites were directly proportional to the dose from chocolate (21 ,41) . The mechanism by which catechin is absorbed by the small intestine is not known, but catechin probably enters the enterocytes by passive diffusion, and absorption by this mechanism should be proportional to the concentration (42) . If catechin enters the cell by another mechanism such as facilitated transport, it appears not to be saturated even at concentrations of 100 µmol/L. The paracellular transport of catechin by Caco-2 cells, a well-established model of human intestinal absorption, was recently described (43) . However, paracellular transport was clearly not the mechanism in the rat small intestine, given the extensive metabolism that must occur within the enterocytes.

Intestinal excretion of conjugated metabolites may constitute an important excretion mechanism for some flavonoids. Using the same perfusion model, 67% of quercetin aglycone was absorbed and conjugated by the small intestine, but the majority of absorbed quercetin was then excreted as conjugates back into the intestinal lumen (34) presumably by the multidrug resistance protein pump (30 ,44) . Our results suggest that the efflux of conjugated forms does not occur because only native catechin was present in the perfusion effluent. Therefore, it appears that when catechin is absorbed into the enterocytes, it is converted to metabolites that are then excreted or transported exclusively on the serosal side to the mesenteric blood where they are delivered to the liver.

The composition of metabolites in mesenteric and aortic plasma as well as bile reveals differences in metabolism in different tissues. Glucuronidation and methylation clearly occurred in the small intestine in this study. Sulfated metabolites were present almost exclusively in bile and thus were formed in the liver. Excretion of high amounts of methylated conjugates in bile, as well as their increased proportion in aortic compared with mesenteric plasma, indicates that methylation also occurs in the liver. Piskula and Terao (29) proposed, on the basis of the enzyme activities present in isolated rat tissues, that epicatechin is glucuronidated in the intestine and then sulfated in the liver, and methylated in the liver and possibly the kidney. We also conclude that glucuronidation is the major conjugation process that occurs in the small intestine and that sulfation and methylation occur in the liver. In addition, methylation occurred in the small intestine, as has been previously described for flavonoids (33 ,34 ,45) .

A schematic representation of the possible mechanisms of absorption and metabolism of catechin in rats is shown in Figure 3 . Absorbed catechin enters intestinal epithelial cells where it is always glucuronidated and sometimes methylated. Apparently, some of the glucuronides are able to enter hepatocytes as has been described for other glucuronides (46 ,47) . Manach et al. (37) reported that after feeding rats catechin, only half of the catechin was glucuronidated in liver samples, suggesting that some glucuronides are deglucuronidated and then reglucuronidated in the liver, but this may occur only if preexisting glucuronides have access to ß-glucuronidases in the endoplasmic reticulum (37 ,47) . Nevertheless, it appears that in the cytosol of hepatocytes, catechin glucuronides are sulfated and/or methylated and are eliminated extensively by bile. The circulating forms are then exclusively glucuronide conjugates of catechin and 3'OMC. If metabolism also occurs in the kidneys as suggested by Piskula and Terao (29) , the metabolites are likely excreted by urine immediately after. Metabolism by other tissues cannot be excluded, although this was not observed in this study.

View larger version (19K): [in this window] [in a new window]   Figure 3. A schematic representation of the possible mechanisms of absorption and metabolism of catechin in rats. Abbreviation: 3'OMC, 3'-O-methyl catechin.

The dose of catechin could affect the composition of individual metabolites. However, no significant differences were observed between the proportions of the conjugate forms at 30 and 100 µmol/L. Complete glucuronidation in the small intestine occurred even at 100 µmol/L. Slightly higher proportions of methylated metabolites existed in both mesenteric and aortic plasma after perfusion with 30 vs. 100 µmol/L, but these differences were not significant (0.05 < P < 0.1). Only a very small amount of sulfate conjugation occurred in the small intestine at both 30 and 100 µmol/L. However, sulfotransferases are generally saturated at much lower concentrations than are glucuronyl transferases (50 ,51) ; whether increased proportions of catechin are conjugated with sulfate in the small intestine after lower doses remains to be determined. Similar proportions of sulfate conjugates in bile were observed after both concentrations, indicating that sulfate conjugation in the liver was not affected by increasing the dose.

From this study, it is clear that the small intestine is the most important organ of glucuronidation and that it also plays a role in the methylation of catechin. The liver was certainly the major site of sulfation as well as additional methylation. We conclude that native catechin enters intestinal epithelial cells, glucuronides enter hepatocytes and that extensive metabolism occurs in both organs in rats. It is essential to further characterize the specific metabolites formed, their subsequent distribution in tissues and cells, as well as their specific biological activities.

	FOOTNOTES

 
² Abbreviations used: COMT, catechol-O-methyltransferase; 3'OMC, 3'-O-methyl catechin; 4'OMC, 4'-O-methyl catechin.

Manuscript received November 27, 2000. Initial review completed January 12, 2001. Revision accepted March 5, 2001.

	REFERENCES

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 

1. Graham H. N. Green tea composition, consumption and polyphenol chemistry. Prev. Med. 1992;21:334-350[Medline]

2. Guyot S., Marnet N., Laraba D., Sanoner P., Drilleau J.-F. Reversed-phase HPLC following thiolysis for quantitative estimation and characterization of the four main classes of phenolic compounds in different tissue zones of a French cider apple variety (Malus domestica Var. Kermerrien). J. Agric. Food Chem. 1998;46:1698-1705

3. Hammerstone J. F., Lazarus S. A., Mitchell A. E., Rucker R., Schmitz H. H. Identification of procyanidins in cocoa (Theobroma cacao) and chocolate using high-performance liquid chromatography mass spectrometry. J. Agric. Food Chem. 1999;47:490-496[Medline]

4. Ritchey J. G., Waterhouse A. L. A standard red wine: monomeric phenolic analysis of commercial Cabernet Sauvignon wines. Am. J. Enol. Vitic. 1999;50:91-100[Abstract/Free Full Text]

5. Haslam E. Practical Polyphenolics—From Structure to Molecular Recognition and Physiological Action 1998:23-31 Cambridge University Press Cambridge, UK.

6. Santos-Buelga C., Scalbert A. Proanthocyanidins and tannin-like compounds: nature, occurrence, dietary intake and effects on nutrition and health. J. Food Sci. Agric. 2000;80:1094-1117

7. Scalbert A., Williamson G. Dietary intake and bioavailability of polyphenols. J. Nutr. 2000;130:2073S-2085S[Abstract/Free Full Text]

8. Waterhouse A. L., Shirley J. R., Donovan J. L. Antioxidants in chocolate. Lancet 1996;348:834(abs)[Medline]

9. Damianaki A., Bakogeorgou E., Kampa M., Notas G., Hatzoglou A., Panagiotou S., Gemetzi C., Kouroumalis E., Martin P. M., Castanas E. Potent inhibitory action of red wine polyphenols on human breast cancer cells. J. Cell. Biochem. 2000;78:429-441[Medline]

10. Pingzhang Y., Jinying Z., Shujun C., Hara Y., Quingfan Z., Zhengguo L. Experimental studies of the inhibitory effects of green tea catechin on mice large intestinal cancers induced by 1,2-dimethylhydrazine. Cancer Lett 1994;79:33-38[Medline]

11. Liao S. S., Umekita Y., Guo J. T., Kokontis J. M., Hiipakka R. A. Growth inhibition and regression of human prostate and breast tumors in athymic mice by tea epigallocatechin gallate. Cancer Lett 1995;96:239-243[Medline]

12. Clifford A. J., Ebeler S. E., Ebeler J. D., Bills N. D., Hinrichs S. H., Teissedre P. L., Waterhouse A. L. Delayed tumor onset in transgenic mice fed an amino acid-based diet supplemented with red wine solids. Am. J. Clin. Nutr. 1996;64:748-756[Abstract/Free Full Text]

13. Hayek T., Fuhrman B., Vaya J., Rosenblat M., Belinky P., Coleman R., Elis A., Aviram M. Reduced progression of atherosclerosis in apolipoprotein E-deficient mice following consumption of red wine, or its polyphenols quercetin or catechin, is associated with reduced susceptibility of LDL to oxidation and aggregation. Arterioscler. Thromb. Vasc. Biol. 1997;17:2744-2752[Abstract/Free Full Text]

14. Xu R., Yokoyama W. H., Irving D., Rein D., Walzem R., German J. B. Effect of dietary catechin and vitamin E on aortic fatty streak development in hypercholesterolemic hamsters. Atherosclerosis 1998;137:29-36[Medline]

15. Putter M., Grotemeyer K. H., Wurthwein G., Araghi-Niknam M., Watson R. R., Hosseini S., Rohdewald P. Inhibition of smoking-induced platelet aggregation by aspirin and pycnogenol. Thromb. Res. 1999;95:155-161[Medline]

16. Rein D., Lotito S., Holt R. R., Keen C. L., Schmitz H. H., Fraga C. G. Epicatechin in human plasma: in vivo determination and effect of chocolate consumption. J. Nutr. 2000;130:2109S-2114S[Abstract/Free Full Text]

17. Rein D., Paglieroni T. G., Pearson D. A., Wun T., Schmitz H. H., Gosselin R., Keen C. L. Cocoa and wine polyphenols modulate platelet activation and function. J. Nutr. 2000;130:2120S-2126S[Abstract/Free Full Text]

18. Hackett A. M., Griffiths L. A., Broillet A., Wermeille M. The metabolism and excretion of (+)-[¹⁴C]cyanidol-3 in man following oral administration. Xenobiotica 1983;13:279-286[Medline]

19. Lee M.-J., Wang Z.-Y., Li H., Chen L., Sun Y., Gobbo S., Balentine D. A., Yang C. S. Analysis of plasma and urinary tea polyphenols in human subjects. Cancer Epidemiol. Biomark. Prev. 1995;4:393-399[Abstract]

20. Donovan J. L., Bell J. R., Kasim-Karakas S., German J. B., Walzem R. L., Hansen R. J., Waterhouse A. L. Catechin is present as metabolites in human plasma after consumption of red wine. J. Nutr. 1999;129:1662-1668[Abstract/Free Full Text]

21. Richelle M., Tavazzi I., Enslen M., Offord E. A. Plasma kinetics in man of epicatechin from black chocolate. Eur. J. Clin. Nutr. 1999;53:22-26[Medline]

22. Boutin J. A., Thomassin J., Seist G., Cartier A. Heterogeneity of hepatic microsomal UDP-glucuronosyltransferase activities. Biochem. Pharmacol. 1985;34:2235-2249[Medline]

23. Strassburg C. P., Nguyen N., Manns M. P., Tukey R. H. UDP-glucuronosyltransferase activity in human liver and colon. Gastroenterology 1998;116:149-160[Medline]

24. Shali N. A., Curtis C. G., Powell G. M., Roy A. B. Sulfation of the flavonoids quercetin and catechin by rat liver. Xenobiotica 1991;21:881-893[Medline]

25. Matsui M., Homma H. Biochemistry and molecular biology of drug-metabolizing sulfotransferase. Int. J. Biochem. 1994;26:1237-1247[Medline]

26. Floché L. Catechol-O-methyltransferase. Int. Pharmacopsychiatry 1974;9:52-60[Medline]

27. Liska D. J. The detoxification enzyme systems. Altern. Med. Rev. 1998;3:187-198[Medline]

28. Sfakianos J., Coward L., Kirk M., Barnes S. Intestinal uptake and biliary excretion of the isoflavone genistein in rats. J. Nutr. 1997;127:1260-1268[Abstract/Free Full Text]

29. Piskula M. K., Terao J. Accumulation of (-)-epicatechin metabolites in rat plasma after oral administration and distribution of conjugation enzymes in rat tissues. J. Nutr. 1998;128:1172-1178[Abstract/Free Full Text]

30. Walle U. K., Galijatovic A., Walle T. Transport of the flavonoid chrysin and its conjugated metabolites by the human intestinal cell line Caco-2. Biochem. Pharmacol. 1999;58:431-438[Medline]

31. Spencer J. P., Chowrimootoo G., Choudhury R., Debnam E. S., Srai S. K., Rice-Evans C. The small intestine can both absorb and glucuronidate luminal flavonoids. FEBS Lett 1999;458:224-230[Medline]

32. Gee J. M., DuPont S. M., Day A. J., Plumb G. W., Williamson G., Johnson I. T. Intestinal transport of quercetin glycosides in rats involves both deglycoslylation and interaction with the hexose transport pathway. J. Nutr. 2000;130:2765-2771[Abstract/Free Full Text]

33. Kuhnle G., Spencer J.P.E., Schroeter H., Shenoy B., Debnam E. S., Srai K. S., Rice-Evans C., Hahn U. Epicatechin and catechin are O-methylated and glucuronidated in the small intestine. Biochem. Biophys. Res. Commun. 2000;277:507-512[Medline]

34. Crespy V., Morand C., Manach C., Besson C., Demigné C., Rémésy C. Part of quercetin absorbed in the small intestine is conjugated and further secreted in the intestinal lumen. Am. J. Physiol. 1999;277:G120-G126[Abstract/Free Full Text]

35. Donovan J. L., Luthria D. L., Stremple P., Waterhouse A. L. Analysis of (+)-catechin, (-)-epicatechin and their 3'- and 4'-O-methylated analogs. A comparison of sensitive methods. J. Chromatogr. B 1999;2:277-283

36. Lopez H. W., Coudray C., Bellanger J., Younes H., Demigné C., Rémésy C. Intestinal fermentation lessens the inhibitory effects of phytic acid on mineral utilization in rats. J. Nutr. 1998;128:1192-1198[Abstract/Free Full Text]

37. Manach C., Texier O., Morand C., Crespy V., Regerat F., Demigné C., Rémésy C. Comparison of the bioavailability of quercetin and catechin in rats. Free Radic. Biol. Med. 1999;27:1259-1266[Medline]

38. Hackett A. M., Shaw I. C., Griffiths L. A. 3'-O-Methyl-(+)-catechin glucuronide and 3'-O-methyl-(+)-catechin sulphate: new urinary metabolites of (+)-catechin in the rat and the marmoset. Experientia 1982;38:538-540[Medline]

39. Shaw I. C., Griffiths L. A. Identification of the major biliary metabolite of (+)-catechin in the rat. Xenobiotica 1980;8:557(abs)

40. Mahé S., Huneau J. F., Marteau P., Thuillier F., Tomé D. Gastroileal nitrogen and electrolyte movements after bovine milk ingestion in humans. Am. J. Clin. Nutr. 1992;56:410-416[Abstract/Free Full Text]

41. Wang J. F., Schramm D. D., Holt R. R., Ensunsa J. L., Fraga C. G., Schmitz H. H., Keen C. L. A dose-response effect from chocolate consumption on plasma epicatechin and oxidative damage. J. Nutr. 2000;130:2115S-2119S[Abstract/Free Full Text]

42. Rozman K. K., Klaassen C. D. Absorption, distribution, and excretion of toxicants. Klaassen C. D. Amdur M. O. Doull J. eds. Casarett and Doull’s Toxicology: The Basic Science of Poisons 1996:91-112 McGraw-Hill New York, NY.

43. Déprez S., Mila I., Scalbert A., Huneau J.-F., Tomé D. Transport of proanthocyanidin dimer, trimer and polymer across monolayers of human intestinal epithelial Caco-2 cells. J. Nutr. 2001;(in press)

44. Walgren R. A., Karnaky K. J., Jr, Lindenmayer G. E., Walle T. Efflux of dietary flavonoid quercetin 4'-ß-glucoside across human intestinal Caco-2 cell monolayers by apical multidrug resistance-associated protein-2. J. Pharmacol. Exp. Ther. 2000;294:830-836[Abstract/Free Full Text]

45. Galijatovic A., Otake Y., Walle U. K., Walle T. Extensive metabolism of the flavonoid chrysin by human Caco-2 and Hep G2 cells. Xenobiotica 1999;29:1241-1256[Medline]

46. Meier P. J., Eckhardt U., Schroeder A., Hagenbuch B., Steiger B. Substrate specificity of sinusoidal bile acid and organic anion uptake systems in rat and human liver. Hepatology 1997;26:1667-1677[Medline]

47. Csala M., Banhegyi G., Braun L., Szirmai R., Burchell A., Burchell B., Benedetti A., Mandl J. ß-Glucuronidase latency in isolated murine hematocytes. Biochem. Pharmacol. 2000;59:801-805[Medline]

48. Wermeille M., Turin E., Griffiths L. A. Identification of the major urinary metabolites of (+)-catechin and 3-O-methyl-(+)-catechin in man. Eur. J. Drug Metab. Pharmacokinet. 1983;8:77-84[Medline]

49. Nielsen S. E., Breinholt V., Justesen U., Cornett C., Dragsted L. O. In vitro biotransformation of flavonoids by rat liver microsomes. Xenobiotica 1998;28:389-401[Medline]

50. Mulder G. J., Jakobey W. B. Sulfation. Conjugation Reactions in Drug Metabolism 1990:107-161 Taylor & Francis London, UK.

51. Oddy E. A., Manchee G. R., Coughtrie M.W.H. Assessment of rat liver slices as a suitable model system for studying the simultaneous sulphation and glucuronidation of phenolic xenobiotics. Xenobiotica 1997;27:369-377[Medline]

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