Investigation of pharmacokinetic parameters of bakuchicin isolated from Psoralea corylifolia in mice.

Bakuchicin is a furanocoumarin isolated from the seeds of Psoralea corylifolia, which is used in oriental medicine. However, limited information on the pharmacokinetics of bakuchicin is available and in addition, no determined method has been devised to quantify bakuchicin levels in the plasma. In the present study, we developed and validated a quantification method using liquid chromatography (LC) coupled with tandem mass spectrometry (LC-MS/MS), which was applied to a pharmacokinetic investigation in mouse plasma. LC was performed using an ACE 5 C18 column, and a mixture of acetonitrile and water containing 0.1% formic acid was used as the mobile phase at a flow rate of 220µL/min. Bakuchicin transition ions in multiple reaction-monitoring modes using positive ionization were observed at m/z 187.0 to m/z 131.0. Bakuchicin and the internal standard (reserpine) had retention times of 4.5 and 4.3min, respectively. Acceptable linearity (r2=0.996) was observed over the concentration range of 20-1000ng/mL, with a lower quantification limit of 20ng/mL in mouse plasma. This method was successfully applied to determine the pharmacokinetic parameters of bakuchicin in mouse plasma and showed that the bioavailability of bakuchicin was 58.3% at 5mg/kg oral administration.

Decreased absorption of midazolam in the stomach due to low pH induced by co-administration of Banha-sasim-tang.

OBJECTIVES: Banha-sasim-tang (BST), which consists of seven different herbs, is one of the most popular herbal formulae for treating gastrointestinal disorders in Eastern Asia. The commonly used herbal medicine is often co-administered with other therapeutic drugs, which raises the possibility of herb-drug interactions and may modify the clinical safety profile of therapeutic drugs. METHODS: We investigated the potential herb-drug interactions between BST extract and midazolam (MDZ) in mice. The area under the plasma concentration-time curve (AUC) of MDZ and 1ʹ-hydroxymidazolam (1ʹ-OH-MDZ) was evaluated for both oral and intraperitoneal administration of MDZ, following oral administration of BST (0.5 and 1 g/kg). RESULTS: It was found that the AUC of MDZ and 1ʹ-OH-MDZ was lower in case of oral administration of MDZ. Administration of BST extract was not associated with hepatic cytochrome P450 activity. BST extract induced a strong reduction in pH and it has been reported that oral mucosal absorption of MDZ is lower at low pH. The decreased absorption rate of MDZ might be caused by the ingredients of BST and may not be related to other factors such as increased excretion of MDZ by P-glycoprotein. CONCLUSIONS: The altered pharmacokinetics of midazolam caused by co-administration with BST in vivo could be attributed to a decrease in pH and subsequent reduction of MDZ absorption rate.