A sensitive, simple, and accurate method for the determination and pharmacokinetic study of vanillic acid in rat plasma was developed using reverse-phase HPLC with UV detection after oral administration of the traditional Chinese medicine preparation of the Di-Gu-Pi decoction. Plasma samples taken from rats were extracted with methanol. The constituent vanillin acid was separated on a C18 stationary phase and a mobile phase of acetonitrile-water (15:85, v/v) (adjusted to pH 3.0 using phosphoric acid), with a UV detector setting at 260 nm. The validated HPLC method developed was used to determine the pharmacokinetic profile of vanillin acid in rat plasma after administration of the Di-Gu-Pi decoction.

In this study, the quantitative analysis of saikosaponins from Radix Bupleuri in China was performed by high performance liquid chromatography. Saikosaponin-a and-d were converted completely into saikosaponin-b1 and -b2 by mild acid treatment. Distinctive measuring of these converted diene-saponins provided a rapid and selective method for the determination of saikosaponin-a and-d in commercial samples of Radix Bupleuri. The conditions of extraction and conversion of saikosaponins were optimized using orthogonal design L9 (34). The HPLC analysis was performed on ODS-C18 column with a flow rate of 1.0ml/min and detection wavelength of 250 nm. Well resolved chromatograms of saikosaponin-b1 and-b2 were obtained with an isocratic elution of ace-tonitrile:1%formic acid water (37.5:62.5). Calibration curves of saikosaponin-b1 and-b2 were linear in the range of 4.9-98.0