Degradation of quercetin-3-glucoside in gnotobiotic rats associated with human intestinal bacteria

Abstract

Aim: The two bacterial species, Eubacterium ramulus and Enterococcus casseli¯avus, which had previously been isolated from human faeces using the¯avonoid quercetin-3-glucoside as the growth substrate, were tested for their ability to utilize this compound in vivo. Methods and Results: Germ-free rats were associated with Eu. ramulus and subsequently with Ent. casseli¯avus and vice versa. Identi®cation and enumeration of the bacterial cell counts in faeces and intestinal contents were performed by whole cell¯uorescence in situ hybridization. Eubacterium ramulus and Ent. casseli¯avus occurred in caecal and colonic contents at cell counts of up to 10 10 g À1 dry weight. In the jejunum, only Ent. casseli¯avus was found (10 9 g À1 dry weight). Upon oral administration of 32 mmol quercetin-3-glucoside, quercetin was detected in the faeces and urine of germ-free rats (2Á2 Â 10 À1 À8Á1 Â 10 À1 mmol 24-h À1 faeces collection and 1Á0 Â 10 À2 À2Á8 Â 10 À1 mmol 24-h À1 urine collection, respectively) and of rats monoassociated with Ent. casseli¯avus (7Á9 Â 10 À1 À2Á7 mmol 24-h À1 faeces and 1Á0 Â 10 À1 À5Á9 Â 10 À1 mmol 24-h À1 urine, respectively). In contrast, the faeces and urine of rats associated with Eu. ramulus contained 3,4-dihydroxyphenylacetic acid (4Á7 Â 10 À2 À3Á6 mmol 24-h À1 faeces and 2Á4 Â 10 À2 À1Á0 mmol 24-h À1 urine, respectively) but only low, or undetectable, concentrations of faecal quercetin (up to 9Á3 Â 10 À2 mmol 24-h À1 faeces; detection limit 2Á5 Â 10 À2 mmol). Urinary quercetin concentrations varied markedly from undetectable amounts up to 1Á0 mmol 24-h À1 urine (detection limit 1Á0 Â 10 À2 mmol). Isorhamnetin was found in the urine of all animals independent of their bacterial status. There were no signi®cant differences between the groups (2Á0 Â 10 À2 À2Á8 Â 10 À1 mmol 24-h À1 urine). In complete intestinal tissues of animals, associated with both species, quercetin-3-glucoside and its metabolites were detected by a more sensitive and selective method at concentrations that were two to three orders of magnitude lower than in faeces or urine. Conclusions: These results indicate that Eu. ramulus may be a key organism for the bacterial transformation of¯avonoids in the gut.

Metabolism of Flavonoids via Enteric Recycling: Role of Intestinal Disposition

“…Which one of these two recycling processes is more important in the disposition of flavonoids has not been determined. However, the important role played by the intestinal microflora in these recycling processes has been confirmed by Schneider et al (2000) who showed significant differences in the pattern of flavonoid metabolites recovered in urine, depending on whether or not bacteria are present in the gut. It is generally believed that these recycling processes may provide a prolonged exposure period for dietary flavonoids.…”

Impact of Gut Microbiota on Intestinal and Hepatic Levels of Phase 2 Xenobiotic-Metabolizing Enzymes in the Rat

“…Cycasin is hydrolytically activated by bacterial enzymes in conventional rats but is excreted unchanged in germ-free animals. Differences in biotransformation between germ-free and conventional animals or animals associated with specific microbial species have also been reported for many other xenobiotics, including propachlor (Bakke et al, 1980), 1-nitropyrene (El-Bayoumy et al, 1983), and quercetin (Schneider et al, 2000). A direct involvement of bacterial enzymes in the biotransformation has been demonstrated for some of these compounds.…”

Plant-Derived Agents with Anti-Glycation Activity

“…It is found in fruits, vegetables and plant-derived beverages such as tea and wine [122]. Gut microflora in the large intestine metabolize rutin to a variety of compounds that include quercetin and phenol derivatives such as 3,4-dihydroxyphenylacetic acid (DHPAA), 3,4-dihydroxytoluene (DHT), 3-hydroxyphenylacetic acid (HPAA), and 4-hydroxy-3-methoxyphenylacetic acid (homovanillic acid, HVA) [122][123][124]. Rutin metabolites, particularly those that include vicinal hydroxyl groups in their structure such as 3,4-dihydroxyphenylacetic acid (DHPAA) and 3,4-dihydroxytoluene (DHT), are powerful inhibitors of the formation of CML and fluorescent derivatives (370-440 nm and 335-385 nm) in histone H1 caused by ADP-ribose.…”