title: CYP2C19 progress curve analysis and mechanism-based inactivation by three methylenedioxyphenyl compounds.
abstract: Several in vitro criteria were used to assess whether three methylenedioxyphenyl (MDP) compounds, the isoquinoline alkaloids bulbocapnine, canadine, and protopine, are mechanism-based inactivators of CYP2C19. The recently reported fluorometric CYP2C19 progress curve analysis approach was applied first to determine whether these alkaloids demonstrate time-dependent inhibition. In this experiment, bulbocapnine, canadine, and protopine displayed time dependence and saturation in their inactivation kinetics with K(I) and k(inact) values of 72.4 ± 14.7 μM and 0.38 ± 0.036 min(-1), 2.1 ± 0.63 μM and 0.18 ± 0.015 min(-1), and 7.1 ± 2.3 μM and 0.24 ± 0.021 min(-1), respectively. Additional studies were performed to determine whether other specific criteria for mechanism-based inactivation were fulfilled: NADPH dependence, irreversibility, and involvement of a catalytic step in the enzyme inactivation. CYP2C19 activity was not significantly restored by dialysis when it had been inactivated by the alkaloids in the presence of a NADPH-regenerating system, and a metabolic-intermediate complex-associated increase in absorbance at approximately 455 nm was observed. In conclusion, the CYP2C19 progress curve analysis method revealed time-dependent inhibition by these alkaloids, and additional experiments confirmed its quasi-irreversible nature. This study revealed that the CYP2C19 progress curve analysis method is useful for identifying novel mechanism-based inactivators and yields a wealth of information in one run. The alkaloids bulbocapnine, canadine, and protopine, present in herbal medicines, are new mechanism-based inactivators and the first MDP compounds exhibiting quasi-irreversible inactivation of CYP2C19.
authors: School of Pharmacy, Faculty of Health Sciences, University of Eastern Finland, P.O. Box 1627, 70211 Kuopio, Finland. kaisa.salminen@uef.fi
authors: Kaisa A
authors: KA
authors: Salminen
authors: Achim
authors: A
authors: Meyer
authors: Peter
authors: P
authors: Imming
authors: Hannu
authors: H
authors: Raunio
mesh_terms: D001060:Aporphines / Q000494:pharmacology*; D001189:Aryl Hydrocarbon Hydroxylases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D053119:Benzophenanthridines / Q000494:pharmacology*; D001599:Berberine / Q000031:analogs & derivatives* / Q000494:pharmacology; D001600:Berberine Alkaloids / Q000494:pharmacology*; D065731:Cytochrome P-450 CYP2C19; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006801:Humans
chemical_list: D001060:Aporphines; D053119:Benzophenanthridines; D001600:Berberine Alkaloids; D004791:Enzyme Inhibitors; D001599:Berberine; D001189:Aryl Hydrocarbon Hydroxylases; C045793:CYP2C19 protein, human; D065731:Cytochrome P-450 CYP2C19; C083807:bulbocapnine; C009093:protopine; C004645:canadine