title: In vitro investigation of cytochrome P450-mediated metabolism of dietary flavonoids.
abstract: Human and mouse liver microsomes and membranes isolated from Escherichia coli, which expressed cytochrome P450 (CYP) 1A2, 3A4, 2C9 or 2D6, were used to investigate CYP-mediated metabolism of five selected dietary flavonoids. In human and mouse liver microsomes kaempferol, apigenin and naringenin were hydroxylated at the 3'-position to yield their corresponding analogs quercetin, luteolin and eriodictyol, whereas hesperetin and tamarixetin were demethylated at the 4'-position to yield eriodictyol and quercetin, respectively. Microsomal flavonoid metabolism was potently inhibited by the CYP1A2 inhibitors, fluvoxamine and -naphthoflavone. Recombinant CYP1A2 was capable of metabolizing all five investigated flavonoids. CYP3A4 recombinant protein did not catalyze hesperetin demethylation, but showed similar metabolic profiles for the remaining compounds, as did human microsomes and recombinant CYP1A2, although the reaction rates in general were lower as compared to CYP1A2. CYP2C9 catalyzed the 4'-demethylation of tamarixetin, whereas CYP2D6 did not seem to play any role in the metabolism of the selected flavonoids. The major involvement in flavonoid metabolism of human CYP1A2, which mediates the formation of metabolites with different biochemical properties as compared to the parent compound and furthermore is known to be expressed very differently among individuals, raises the important question of whether individual differences in the CYP enzyme activity might affect the beneficial outcome of dietary flavonoids, rendering some individuals more or less refractory to the health-promoting potential of dietary flavonoids.
authors.affiliation: Institute of Food Safety and Toxicology, Division of Biochemical and Molecular Toxicology, Danish Veterinary and Food Administration, Mørkhøj Bygade 19, 2860 Søborg, Denmark. vib@fdir.dk
authors.forename: V M
authors.initials: VM
authors.lastname: Breinholt
authors.forename: E A
authors.initials: EA
authors.lastname: Offord
authors.forename: C
authors.initials: C
authors.lastname: Brouwer
authors.forename: S E
authors.initials: SE
authors.lastname: Nielsen
authors.forename: K
authors.initials: K
authors.lastname: Brøsen
authors.forename: T
authors.initials: T
authors.lastname: Friedberg
mesh_terms: D000818:Animals; D001711:Biotransformation; D065607:Cytochrome P-450 Enzyme Inhibitors; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D004032:Diet; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D005419:Flavonoids / Q000378:metabolism*; D005504:Food Analysis; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D008566:Membranes / Q000201:enzymology; D051379:Mice; D008810:Mice, Inbred C57BL; D008862:Microsomes, Liver / Q000201:enzymology; D011994:Recombinant Proteins / Q000378:metabolism; D013045:Species Specificity
chemical_list: D065607:Cytochrome P-450 Enzyme Inhibitors; D004791:Enzyme Inhibitors; D005419:Flavonoids; D011994:Recombinant Proteins; D003577:Cytochrome P-450 Enzyme System