The pharmacokinetics and oral bioavailability studies of columbianetin in rats after oral and intravenous administration.

Ethnopharmacological Relevance: The roots of Angelica pubescens Maxim. f. biserrata Shan et Yuan (RAP) has been used as Traditional Chinese medicine to treat rheumatic disease in China since ancient times, but its action mechanisms was not well understood. Columbianetin is one of the main active constituents isolated from RAP, which has been shown to have various biological activities, but the absorption characteristics and oral bioavailability dose proportionality of columbianetin in vivo were not studied.

Materials And Methods: Male Sprague Dawley rats (210-230 g) received either an intravenous (i.v. 5, 10 and 20 mg kg(-1)) or oral (5, 10 and 20 mg kg(-1)) dose of columbianetin. The levels of columbianetin in plasma were measured by a simple and sensitive reversed-phase high-performance liquid chromatography (HPLC) method. The simple liquid-liquid extraction with ethyl acetate was used for sample preparation. Osthole was selected as internal standard (IS).

Results: The chromatographic separation was accomplished on a C18 column at a flow rate of 1 mL min(-1), where water-methanol was used as mobile phase. The calibration curve of the method was linear in the concentration range of 0.05-2000 μg mL(-1). The intra and inter-day accuracy for columbianetin in rat plasma samples were within 8% and the variation was less than 8.3%. This method was suitable for the determination and pharmacokinetic study of columbianetin in rat plasma after both intravenous and oral administration. The results indicated that maximum plasma concentrations(Cmax) for the columbianetin (17-42 μg mL(-1)) were achieved at 0.3-0.5h post-oral dosing and the apparent volume of distribution (V/F) ranged from 0.38 to 0.44 L. Absolute bioavailability of columbianetin was assessed to be 81.13 ± 45.85, 81.09 ± 33.63 and 54.30 ± 23.19%, respectively. Terminal elimination half-life (T1/2) of the columbianetin after oral dosing was 60-90 min and were 2.5-3.3 fold longer than those observed for the i.v. dosing.

Conclusions: The pharmacokinetic properties of columbianetin in rat after oral administration were characterized as rapid oral absorption, quick clearance and good absolute bioavailability. The bioavailability of columbianetin ranged from 54 to 81% for 5, 10 and 20 mg kg(-1) oral doses. The bioavailability of columbianetin is independent of the doses studied. Columbianetin showed dose proportionality over the dose range 5-20 mg kg(-1). The results clearly demonstrated that columbianetin was one of the material bases of RAP. Furthermore, an HPLC method was demonstrated in this study for the research of traditional Chinese medicine.