Metabolite profiling and identification of enzymes responsible for the metabolism of hirsutine, a major alkaloid from Uncaria rhynchophylla

Abstract

1. The in vitro metabolism of hirsutine was determined using liver microsomes and human recombinant cytochrome P450 enzymes. Under the current conditions, a total of 14 phase I metabolites were tentatively identified.

2. Ketoconazole showed significant inhibitory effect on the metabolism of hirsutine. Human recombinant cytochrome P450 enzyme analysis revealed that metabolism of hirsutine was mainly catalysed by CYP3A4.

3. Our data revealed that hirsutine was metabolised via mono-oxygenation, di-oxygenation, N-oxygenation, dehydrogenation, demethylation and hydrolysis.

4. In glutathione (GSH)-supplemented liver microsomes, four GSH adducts were identified. Hirsutine underwent facile P450-mediated metabolic activation, forming reactive 3-methyleneindolenine and iminoquinone intermediates.

5. This study provided valuable information on the metabolic fates of hirsutine in liver microsomes, which would aid in understanding the hepatotoxicity caused by hirsutine or hirsutine-containing herb preparation.

Keywords:

• Hirsutine
• metabolic pathway
• 3-methyleneindolenine
• iminoquinone
• LC-HRMS

Authors’ contributions

Experiment was designed by: Yiqing Guo, Zenghong Jiang. Experiment was performed by: Yiqing Guo, Huanhuan Lv. Data were analysed by: Yiqing Guo, Jing Lv. Manuscript was written by: Yiqing Guo. Manuscript was reviewed by: Zenghong Jiang.

Disclosure statement

The authors reported no conflict of interest.

Additional information

Funding

This work was not funded.