Abstract: AIM: To develop an accurate, sensitive and reliable HPLC MS detection method for the ginsenoside Rg1, and to study the absorption characteristics of Rg1 in different intestinal sections (ileumand jejunum) and the influence of p-glycoprotein on the absorption rate. METHODS: Rat everted gut sac system was used. Sac containing drug free Krebs solution was immersed into the Krebs solution containing 20 mg·mL^-1 Rg1.The solution inside the sac was collected and drug concentration was determined by validated ESI-HPLC-MS method.Verapamil, a p-glycoprotein inhibitor, was used to study the influence of p-glycoprotein on the absorption of Rg1. RESULTS: The Rg1 concentration in the sac was increasing according to the time and there is no difference of the absorption rate between ileum and jejunum.Verapamil had no effect on the absorption of Rg1 in sac system. CONCLUSION: There is no difference for Rg1 absorption between ileum and jejunum of rat.Rg1 might not be the substrate of p-glycoprotein.

Key words: ginsenoside, Rg1, everted gut sac, absorption, verapamil, HPLC MS