Thymoquinone Increased Warfarin 7-hydroxylation in Human Liver Microsomes and Induced the Expression of CYP2C9 in HepG2 Cells

Herb-drug interaction is an interesting phenomenon that can induce therapeutic complications in patients. Warfarin is widely used as an anticoagulant, which has a narrow therapeutic index. The combination of herbal and warfarin has consequences in the therapy outcome on the attenuation of drug efficacy or increased toxicity. This study aimed to investigate the effect of thymoquinone on warfarin 7-hydroxylation activity in the human liver microsome (HLM) and CYP2C9 expression in HepG2 cells. The co-administration of thymoquinone on warfarin 7-hydroxylation was investigated using HLM and HepG2 cells. The study was divided into three groups: control, warfarin, and combination of warfarin-thymoquinone. The metabolite of 7-hydroxywarfarin (7-OH warfarin) in HLM was determined using HPLC-MS/MS. Furthermore, the effect of thymoquinone in terms of the induction of CYP2C9 expression in HepG2 cells was determined by RT-PCR. The results of the validated method used were selective for HLM 7hydroxywarfarin, with an LLOQ of 0.62 mu M, so it met the criteria for accuracy and precision for metabolite analysis. The results showed that the coincubation of thymoquinone at 0.37mM significantly increased warfarin 7hydroxylation activity (P<0.05). In addition, after 72-hour incubation, thymoquinone also significantly induced CYP2C9 expression in HepG2 cells (P<0.05). These findings provide valuable insights that the combination of thymoquinone with warfarin significantly increased the warfarin 7hydroxylation activity in human liver microsomes and CYP2C9 expression in HepG2 cells, which may have an impact on the clinical outcomes of warfarin in patients.