Vinegar-baked Radix Bupleuri (VBRB) is usually used to focus other drugs effect on liver in traditional Chinese medicine (TCM). However, no sufficient scientific data are available to support this concept. In this paper, the liver targeting enhancing effect of VBRB on rhein was investigated. 432 of rats were divided into two large groups according to the dose of rhein, low dose group of rhein (LDGR) and high dose group of rhein (HDGR). In each group, the rats were further divided into four subgroups, rhein control and rhein co-administered with three different doses of VBRB peroral. Concentrations of rhein and its metabolite in different tissues were determined by HPLC. Compared to the control group, VBRB significantly increased the distribution of both rhein and its metabolite in liver and meanwhile decreased their distribution in other tissues, indicating a strong liver targeting enhancing effect. This liver targeting effect of VBRB depended on the dose of VBRB and rhein. Low and high dose of VBRB had a more strong effect than medium dose in HDGR; high dose of rhein was more sensitive than low dose of rhein (P<0.05). Rhein existed in two forms after peroral administration in vivo. It was found that the liver targeting effect of VBRB was more remarkable with the native form of rhein compared to its derivative form. The results of this paper demonstrated that co-administration with VBRB is a simple and efficiencient method for liver targeting therapy, and the meridine guide theory of TCM was credible.
