Inactivation of cytochrome P450 by the food-derived complex phenol oleuropein.
Complex phenols, such as the glycoside oleuropein and hydroxytyrosol, are found in high concentrations in the typical components of the Mediterranean diet. We have previously reported that oleuropein inhibits androstenedione 6 beta-hydroxylase activity, a CYP3A marker in human liver microsomes (Stupans, I., Stretch, G., Hayball, P., 2000. Olive oil phenols inhibit human hepatic microsomal activity. Journal of Nutrition. 130 2367-2370). Oleuropein, but not the structurally similar compounds hydroxytyrosol and secologanin, was found to be a mechanism-based inhibitor of androstenedione 6 beta-hydroxylase activity. Preincubation with 100 microM oleuropein and NADPH resulted in a significantly lower androstenedione 6 beta-hydroxylase activity when compared to preincubation carried out with oleuropein without NADPH, 0.11+/-0.01 nmol/mg microsomal protein/min compared with 0.29+/-0.03 nmol/mg microsomal protein/min (P<0.05). The inactivation exhibited pseudo-first-order kinetics. The maximal rate constant for inactivation (k(inactivation)) was calculated to be 0.09 min(-1) and the concentration of inactivator required for half maximal inactivation (Ki) was calculated to be 22.2 microM. Oleuropein was found to be a relatively weak inhibitor of CYP1A2-mediated 7-methoxyresorufin-O-deethylation (24% inhibition at 100 microM oleuropein), but not CYP2E1-mediated chlorzoxazone 6-hydroxylation. CYP1A2 did not undergo mechanism-based inactivation by oleuropein.
Stupans
I
I
Center for Pharmaceutical Research, School of Pharmaceutical, Molecular and Biomedical Sciences, University of South Australia, SA 5000, Australia. ieva.stupens@unisa.edu.au
Murray
M
M
Kirlich
A
A
Tuck
K L
KL
Hayball
P J
PJ
D001189:Aryl Hydrocarbon Hydroxylases; D019363:Cytochrome P-450 CYP1A1 / Q000378:metabolism; D019392:Cytochrome P-450 CYP2E1 / Q000378:metabolism; D051544:Cytochrome P-450 CYP3A; D065607:Cytochrome P-450 Enzyme Inhibitors; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D004032:Diet; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006801:Humans; D066298:In Vitro Techniques; D057888:Iridoid Glucosides; D039823:Iridoids; D007700:Kinetics; D008297:Male; D019083:Mediterranean Region; D008862:Microsomes, Liver / Q000201:enzymology; D009249:NADP / Q000378:metabolism; D010089:Oxidoreductases, N-Demethylating / Q000037:antagonists & inhibitors*; D011714:Pyrans / Q000494:pharmacology*; D013250:Steroid Hydroxylases / Q000378:metabolism
D065607:Cytochrome P-450 Enzyme Inhibitors; D004791:Enzyme Inhibitors; D057888:Iridoid Glucosides; D039823:Iridoids; D011714:Pyrans; C002769:oleuropein; D009249:NADP; D003577:Cytochrome P-450 Enzyme System; D013250:Steroid Hydroxylases; D019392:Cytochrome P-450 CYP2E1; D001189:Aryl Hydrocarbon Hydroxylases; D019363:Cytochrome P-450 CYP1A1; D051544:Cytochrome P-450 CYP3A; C022657:steroid hormone 6-beta-hydroxylase; D010089:Oxidoreductases, N-Demethylating