Modulation of cytochrome P450 enzyme system by selected flavonoids.
OBJECTIVE
The aim of this study was to assess the effect of various flavonoids on the NADPH:cytochrome P450 oxidoreductase (CYPOR) activity in respect of the reduction of different electron acceptors as well as to study an impact of flavonoids on monooxygenation of a model substrate of cytochrome P450 (CYP).


METHODS
The modulation of CYPOR activity was determined spectrophotometrically based on the time course of the reduction of different electron acceptors. The CYP reduction was monitored via its complex formation with CO, having pronounced the absorption maximum at 450 nm. Finally, effect of CYPOR stimulation by 7,8benzoflavone (ANF) on 7pentoxyresorufin Odepentylation was assayed in the microsomal monooxygenation system using the fluorimetric detection of formed resorufin.


RESULTS
The stimulation of CYPOR activity via ANF was found to be associated with following electron acceptors: cytochrome c, potassium ferricyanide, cytochrome b5, but not with CYP. Surprisingly, 5,6benzoflavone, a position isomer of ANF, was ineffective in the CYPOR stimulation as well as the other flavonoids tested. In microsomal preparations, ANF did not markedly enhance the reaction rate of monooxygenation of CYP2B4 model substrate.


CONCLUSIONS
Our results document that among all of the tested flavonoids only ANF is able to stimulate CYPOR activity, however, the ANF-mediated stimulation of CYPOR has no impact on the oxidative metabolism catalyzed by CYP system.
Hodek
Petr
P
Department of Biochemistry, Charles University, Prague, Czech Republic. hodek@natur.cuni.cz
Tepla
Martina
M
Krizkova
Jitka
J
Sulc
Miroslav
M
Stiborova
Marie
M
D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D001571:Benzoflavones / Q000737:chemistry / Q000378:metabolism; D002248:Carbon Monoxide / Q000378:metabolism; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D015786:Cytochromes b5 / Q000378:metabolism; D045304:Cytochromes c / Q000378:metabolism; D005292:Ferricyanides / Q000378:metabolism; D005419:Flavonoids / Q000737:chemistry / Q000494:pharmacology*; D005470:Fluorometry; D008297:Male; D008861:Microsomes / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D009251:NADPH-Ferrihemoprotein Reductase / Q000378:metabolism*; D010078:Oxazines / Q000378:metabolism; D010084:Oxidation-Reduction / Q000187:drug effects; D011817:Rabbits; D013053:Spectrophotometry; D008063:Thioctic Acid / Q000494:pharmacology; D013997:Time Factors; D019324:beta-Naphthoflavone / Q000737:chemistry / Q000378:metabolism
D000975:Antioxidants; D001571:Benzoflavones; D005292:Ferricyanides; D005419:Flavonoids; D010078:Oxazines; C011512:alpha-naphthoflavone; D019324:beta-Naphthoflavone; C014180:resorufin; D008063:Thioctic Acid; D002248:Carbon Monoxide; D045304:Cytochromes c; D015786:Cytochromes b5; D003577:Cytochrome P-450 Enzyme System; D009251:NADPH-Ferrihemoprotein Reductase; C028033:potassium ferricyanide