Pharmacokinetic studies unveiled the drug-drug interaction between trans-2,3,5,4'-tetrahydroxystilbene-2-O-β-d-glucopyranoside and emodin that may contribute to the idiosyncratic hepatotoxicity of Polygoni Multiflori Radix.

Polygoni Multiflori Radix (PMR) has been a reputable tonifying traditional Chinese medicine for a long history. However, clinical side effects regarding its idiosyncratic hepatotoxicity are occasionally reported. The containing anthraquinones, particularly emodin, could cause liver injury in both in vitro and in vivo experiments. It is well-known that some compounds could influence other compounds' pharmacokinetic parameters significantly. In this work, the influence of trans-2,3,5,4'-tetrahydroxystilbene-2-O-β-d-glucopyranoside (TSG) on the pharmacokinetic behavior of emodin in rats was evaluated by an ultra-high performance liquid chromatography/triple quadrupole mass spectrometry (UHPLC/MS-MS) approach. Pharmacokinetic parameters of emodin, PMR extract, and TSG-free PMR extract (prepared by a component "knock-out" strategy with TSG eliminated), in rats after one-day and seven-day administration were determined and compared. We found that, after seven-day administration of the whole PMR extract (rather than TSG-free extract), emodin in rats was accumulated. And accordingly, the exposure of emodin in rats pre-treated with single TSG for seven days could be significantly enhanced. The results indicate that TSG was able to accelerate the exposure and metabolism of emodin. The effect of TSG on the metabolic activities of cytochrome P450 enzymes was further assessed by an LC-MS cocktail method. The accelerated exposure and metabolism of emodin could result from the up-regulation activity of CYP450s, in particular CYP1A2 isozyme. The findings obtained in this work firstly unveiled DDI between TSG and emodin in the administration of PMR, thus may provide a basis for unveiling the underlying mechanism of PMR-induced liver injury.