Identification of Inhibitory Component in Cinnamon —O-Methoxycinnamaldehyde Inhibits CYP1A2 and CYP2E1—

Abstract

  The Cinnamomi Cortex and Ephedra Herba were found to more strongly inhibit aminopyrine N-demethylation in rat liver microsomes compared to other constituents included in Sho-seiryu-to. The component inhibiting drug oxidations catalyzed by CYP1A2 and CYP2E1 was isolated from Cinnamomi Cortex, and was identified as o-methoxycinnamaldehyde (OMCA). When phenacetin and 4-nitrophenol were used as probe substrates for CYP1A2 and CYP2E1, respectively, the OMCA was shown to be a competitive inhibitor against CYP1A2 while it was a mixed type inhibitor against CYP2E1. The inhibitory effect of OMCA on 4-nitrophenol 2-hydroxylation (K_i=6.3 μM) was somewhat potent compared to that observed on phenacetin O-deethylation (K_i=13.7 μM) in rat liver microsomes.