Deoxypodophyllotoxin (DPT) is a bioactive compound of Anthriscus sylvestris (Apiaceae). In the present study, the inhibition of cytochrome P450 (CYP) by DPT was evaluated in human liver microsomes (HLM) and the baculovirus-insect cell-expressed human CYPs using a cocktail probe assay. When a mixture of specific CYP substrates was incubated with DPT in HLM, CYP2C9-catalyzed diclofenac 4-hydroxylation and CYP3A4-catalyzed midazolam 1-hydroxylation were strongly inhibited by DPT, with IC (50) values of 6.3 and 9.2 microM, respectively. The Lineweaver-Burke plots for the inhibition of CYP2C9 and CYP3A4 in HLM and baculovirus-insect cell-expressed human CYPs were consistent with a competitive type of inhibition. From these results, DPT was characterized to be a competitive inhibitor of CYP2C9 and CYP3A4, with K(i) values of 3.5 and 10.8 microM in HLM and 24.9 and 3.5 microM in baculovirus-insect cell-expressed human CYPs, respectively.
Georg Thieme Verlag KG Stuttgart. New York.