The impact of acacetin on proguanil metabolism: An in vitro and in vivo study.

This study investigated the inhibitory effect of acacetin on the metabolism of proguanil in vitro and in vivo. Rat liver microsomes (RLM), human liver microsomes (HLM) and recombinant human CYP2C19 (rCYP2C19) were utilized to screen for drug-drug interactions (DDI) between proguanil and other drugs. The kinetic parameters and inhibition types were analyzed through substrate inhibition and Lineweaver-Burk plots, quantifying the impact of acacetin on proguanil metabolism. Additionally, pharmacokinetic studies were conducted in rats, and molecular docking was performed to assess the DDI between acacetin and proguanil. Acacetin inhibited the metabolism of proguanil in both RLM and HLM, with an inhibition rate of 80.4 % in RLM and 78.3 % in HLM, respectively. Moreover, the IC50 values were 9.61 ± 0.40, 24.91 ± 2.54 and 1.98 ± 0.35 μM for RLM, HLM and rCYP2C19, respectively. In all systems, acacetin exhibited mixed inhibitory mechanism. Upon co-administration of proguanil and acacetin in vivo, the AUC(0-t) and AUC(0-∞) of proguanil was increased by 41.7 % and 40.6 %, respectively, while plasma clearance (CLz/F) was decreased by 28.8 %. For metabolite, cycloguanil, CLz/F was decreased while AUC(0-t) was increased. Molecular docking confirmed that the inhibitory effect of acacetin on proguanil involved CYP2C19. Acacetin altered the pharmacokinetics of proguanil by inhibiting its CYP2C19-mediated metabolism, as evidenced by its inhibitory effects in RLM, HLM and rCYP2C19. These findings underscored the necessity of considering DDI in clinical settings, particularly between natural compound acacetin and antimalarial therapy of proguanil. Further studies in human subjects are warranted to assess the clinical relevance of these interactions.