Metabolism of quercetin and kaempferol by rat hepatocytes and the identification of flavonoid glycosides in human plasma

• Published in: Xenobiotica Vol. 32; no. 4; pp. 279 - 287
• Main Authors: Oliveira, E. J., Watson, D. G., Grant, M. H.
• Format: Journal Article
• Language: English
• Published: London Informa UK Ltd 2002; Taylor & Francis
• Subjects: Adult; Animals; Biological and medical sciences; Female; Flavonoids - blood; General pharmacology; Glycosides - blood; Hepatocytes - metabolism; Humans; Kaempferols; Male; Medical sciences; Middle Aged; Molecular Structure; Neuroprotective Agents - metabolism; Pharmacognosy. Homeopathy. Health food; Pharmacology. Drug treatments; Quercetin - analogs & derivatives; Quercetin - metabolism; Rats; Rats, Sprague-Dawley; Rat; Metabolite; Glucuronic acid conjugation; Flavonoid; Medicinal plant; Blood plasma; Polyphenol; Hepatocyte; Gymnospermae; Glycoside; Quantitative analysis; Human; Kaempferol; Rodentia; Oral administration; Metabolism; In vitro; Ginkgo biloba; Vertebrata; Mammalia; Animal; Plant origin; Quercetin; Ginkgoales; Spermatophyta
• ISSN: 0049-8254; 1366-5928
• DOI: 10.1080/00498250110107886

1. The metabolism of the flavonoids quercetin and kaempferol by rat hepatocytes was investigated using liquid chromatography coupled with electrospray mass spectrometry (LC-ESI MS). Quercetin and kaempferol were extensively metabolized (98.8 ± 0.1% and 81.0 ± 5.1% respectively, n = 4), with four glucuronides of quercetin and two of kaempferol being detected after incubation. 2. The glucuronides of quercetin and kaempferol formed upon incubation with rat hepatocytes were identified as the same ones formed after incubation with the UDP-glucuronosyltransferase isoform UGT1A9. 3. In addition, plasma samples from human volunteers taken after consumption of capsules of Ginkgo biloba, a plant rich in flavonoid glycosides, were analysed by LC-MS for the presence of flavonoid glucuronides and flavonoid glycosides. Reported is evidence for the presence of flavonoid glycosides in samples of plasma. 4. The results suggest that UGT1A9 is a key UDP-glucuronosyltransferase isoform for the metabolism of flavonoids, and that absorption of intact flavonoid glycosides is possible.