Abstract

1. Evodol is one of the furanoids isolated from the fruits of Evodia rutaecarpa that has been widely prescribed for the treatment of gastrointestinal diseases in China. The aim of this study was to investigate the inhibitory effect of evodol on CYP3A.

2. A 30-min preincubation of evodol with human liver microsomes raised an obvious left IC₅₀ shift, 3.9-fold for midazolam 1’-hydroxylation and 3.2-fold for testosterone 6β-hydroxylation. Evodol inactivated CYP3A in a time-, concentration- and NADPH-dependent manner, with K_I and k_inact of 5.1 μM and 0.028 min⁻¹ for midazolam 1’-hydroxylation and 3.0 μM and 0.022 min⁻¹ for testosterone 6β-hydroxylation.

3. Co-incubation of ketoconazole attenuated the inactivation while the inclusion of glutathione (GSH) and catalase/superoxide dismutase displayed no such protection.

4. cis-Butene-1, 4-dial (BDA) intermediate derived from evodol were trapped by glutathione and N-acetyl-lysine in microsomes and characterised by HR-MS spectra. The BDA intermediate was believed to play a key role in CYP3A inactivation. CYP3A4 and 2C9 were the primary enzymes contributing to the bioactivation of evodol.

5. To sum up, for the first time evodol was characterised as a mechanism-based inactivator of CYP3A.