title: Plasma metabolites of dietary flavonoids after combination meal consumption with onion and tofu in humans.
abstract: METHODS
  The effect of food combination on metabolic profile in postprandial plasma has hardly been reported. We investigated the absorption and metabolism of quercetin and soy isoflavones in humans after combination meal consumption.
  
  
  RESULTS
  Five healthy volunteers ingested sautéed onion and tofu, and the plasma metabolites of quercetin and isoflavones were analyzed. Quercetin and genistein were incubated with human intestinal Caco-2 cells and human hepatoma HepG2 cells to further analyze the influence of simultaneous supply to the small intestine and the liver. Glucuronosyl conjugates of quercetin and methylated quercetin were the major plasma metabolites in the case of onion intake. Plasma metabolites with the single serving of tofu were both glucuronide and sulfate metabolites of isoflavones. Interestingly, quercetin sulfate was only detected after the combined intake of sautéed onion and tofu, accompanied with a decrease in sulfated isoflavones. Besides, quercetin was shown as the preferential substance for phase II enzymes over genistein in both Caco-2 and HepG2 cells.
  
  
  CONCLUSIONS
  These results indicate that, when flavonoids and isoflavonoids were ingested together, the metabolic conversions in the small intestine and/or the liver could be altered, resulting in the variation of the postprandial profiles of the plasma metabolites.
authors.affiliation: Department of Food Science, Graduate School of Nutrition and Bioscience, The University of Tokushima, Tokushima, Japan.
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Nakamura
authors.forename: Kaeko
authors.initials: K
authors.lastname: Murota
authors.forename: Shun
authors.initials: S
authors.lastname: Kumamoto
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Misumi
authors.forename: Noriko
authors.initials: N
authors.lastname: Bando
authors.forename: Shinichi
authors.initials: S
authors.lastname: Ikushiro
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Takahashi
authors.forename: Keiko
authors.initials: K
authors.lastname: Sekido
authors.forename: Yoji
authors.initials: Y
authors.lastname: Kato
authors.forename: Junji
authors.initials: J
authors.lastname: Terao
mesh_terms: D000042:Absorption; D000328:Adult; D018938:Caco-2 Cells; D018592:Cross-Over Studies; D005260:Female; D019833:Genistein / Q000097:blood* / Q000493:pharmacokinetics; D020719:Glucuronides / Q000378:metabolism; D056945:Hep G2 Cells; D006801:Humans; D007421:Intestine, Small / Q000378:metabolism; D007529:Isoflavones / Q000097:blood* / Q000493:pharmacokinetics; D008099:Liver / Q000378:metabolism; D008297:Male; D019697:Onions; D011794:Quercetin / Q000097:blood* / Q000493:pharmacokinetics; D045730:Soy Foods; D055815:Young Adult
chemical_list: D020719:Glucuronides; D007529:Isoflavones; D011794:Quercetin; D019833:Genistein
keywords: Bioavailability; Combination meal; Human metabolites; Isoflavone; Quercetin