Abstract

Background: In the development of a new drug, pre-clinical studies require an efficient, convenient, and reliable evaluation system for metabolite screening and drug-drug interaction (DDI). Our study aimed to establish such a reliable evaluation system using recombinant human CYP2C8 (RHCYP2C8) yeast with the enzyme-selective substrate amodiaquine by optimizing enzyme-catalyzed reaction conditions. Then, we studied the inhibition of Gingerol Soft Capsule (GSC) and 6-gingerol (6G) on CYP2C8 activity.
Methods: RHCYP2C8 yeast whole-cell and microsome reaction systems were established by optimizing enzyme-catalyzed reaction parameters. IC₅₀ values of 6G, GSC, and quercetin were calculated by GraphPad Prism 8.3.0, and their volume per dose index (VDI) values were calculated in order to predict the potential inhibition in vivo.
Results: Our results show that the enzyme kinetic parameters of the whole-cell reaction system for K_m and V_max were 89.77 μmol/L and 0.33 μmol/h•g yeast, the parameters of the microsome reaction system, were 6.20 μmol/L and 0.12 μmol/h•g protein, respectively. IC50 values of quercetin, 6G, and GSC were 6.370, 612.5 μmol/L, and 464 μg/mL, respectively. The VDI values of 6G and GSC <5.0, suggesting low potential for interaction.
Conclusion: The RHCYP2C8 yeast whole-cell reaction system is suitable for the metabolite screening, and the RHCYP2C8 microsome reaction system is efficient for the DDI study. The observed IC₅₀ values of 6G and GSC are unlikely to be achieved in humans with oral administration according to the poor bioavailability documented. Thus, GSC or 6G might not be effective in causing potential DDIs with drugs metabolized by CYP2C8 in humans.