Inhibitory effects of tanshinones towards the catalytic activity of UDP-glucuronosyltransferases (UGTs)

Abstract

Contents: Danshen is a popular herb employed to treat cardiovascular and cerebrovascular diseases worldwide. Danshen–drug interaction has not been well studied.

Objective: The inhibitory effects of four major tanshinones (tanshinone I, tanshinone IIA, cryptotanshinone, and dihydrotanshinone I) on UDP-glucuronosyltransferases (UGTs) isoforms were determined to better understand the mechanism of danshen–prescription drugs interaction.

Materials and methods: In vitro recombinant UGTs-catalyzed 4-methylumbelliferone (4-MU) glucuronidation reaction was employed. Tanshinones (100 μM) was used to perform the initial screening of inhibition capability. High-performance liquid chromatography (HPLC) was used to separate 4-MU and its glucuronide. In vitro–in vivo extrapolation (IV–IVE) was employed to predict in vivo inhibition situation.

Results: Cryptotanshinone inhibited UGT1A7 and UGT1A9 with IC₅₀ values of 1.91 ± 0.27 and 0.27 ± 0.03 μM, respectively. Dihydrotanshinone I inhibited UGT1A9-catalyzed 4-MU glucuronidation reaction with the IC₅₀ value of 0.72 ± 0.04 μM. The inhibition of cryptotanshinone towards UGT1A7 and UGT1A9 was best fit to competitive inhibition type, and UGT1A9 was non-competitively inhibited by dihydrotanshinone I. Using in vitro inhibition kinetic parameters (K_i) and in vivo maximum plasma concentration (C_max) of cryptotanshinone and dihydrotanshinone I, the change of area-under-the-concentration–time curve (AUC) was predicted to be 0.4–4.2%, 3.7–56.3%, and 0.6–6.4% induced by cryptotanshinone and dihydrotanshinone inhibition towards UGT1A7 and UGT1A9, respectively.

Discussion and conclusion: The inhibitory effects of tanshinones towards important UGT isoforms were evaluated in the present study, which provide helpful information for exploring the mechanism of danshen–clinical drugs interaction.

KEYWORD:

• Enzyme inhibition
• herb–drug interaction
• in vitro screening
• in vitro–in vivo extrapolation (IV-IVE)

Acknowledgements

This study was funded by Tianjin Project of Thousand Youth Talents, and Tianjin application foundation and advanced technology research plan (No.15JCYBJC54700).

Disclosure statement

The authors report that they have no conflicts of interest.