Bioavailability of salvianolic acid B in conscious and freely moving rats

Salvianolic acid B is an herbal ingredient isolated from Salvia miltiorrhiza. The aim of this study was to apply an automated blood sampling system coupled to a simple liquid chromatographic system to determine the bioavailability of salvianolic acid B in stress-free rats. The plasma sample (25 μl) was vortex-mixed with 50 μl of internal standard solution (chloramphenicol 10 μg/ml in acetonitrile) to achieve protein precipitation. Salvianolic acid B in the rat plasma was separated using a reversed-phase C18 column (250 mm × 4.6 mm, 5 μm) with a mobile phase of acetonitrile-methanol-20 mM NaH₂PO₄ (adjusted to pH 3.5 with H₃PO₄) (20:10:70 v/v/v) containing 0.1 mM 1-octanesulfonic acid, and the flow-rate of 1 ml/min. The UV detection wavelength was 286 nm. The concentration-response relationship from the present method indicated linearity over a concentration range of 0.5-200 μg/ml. Intra- and inter-assay precision and accuracy of salvianolic acid B fell well within the predefined limits of acceptability (<15%). The plasma sample of salvianolic acid B was further identified by LC-MS/MS in the negative ion mode using mass transition m/z 358.2 to the product ion m/z 196.9. After salvianolic acid B (100 mg/kg, i.v.; 500 mg/kg, p.o.) was given in conscious and freely moving rats, the AUC were 5030 ± 565 and 582 ± 222 min μg/ml for intravenous (100 mg/kg) and oral (500 mg/kg) doses, respectively. The oral bioavailability of salvianolic acid B in freely moving rats was calculated to be 2.3%.