Simultaneous determination of Gastrodin and Ligustrazine hydrochloride in dog plasma by gradient high-performance liquid chromatography.

A novel reversed-phase HPLC method was developed for the simultaneous determination of Gastrodin (Gas) and Ligustrazine hydrochloride (LZH) in dog plasma after oral administration of the preparation 'Tianxiong Capsule'. The assay involves deproteinization, extraction and subsequent detection with a gradient solvent system at two different wavelengths. Retention times were 10.6 and 18.9 min for Gas and LZH, respectively. Linear responses were observed over a wide range (0.40-200.0 microg/ml for Gas and 0.0999-39.96 microg/ml for LZH) in plasma. The mean intra- and inter-assay variation coefficients were 2.7 and 3.4% for Gas and 3.4 and 4.2% for LZH, respectively. The average extract recoveries were 76.77% for Gas and 75.8% for LZH. This assay has been successfully used to provide pharmacokinetic data for Gastrodin with oral administration of Tianxiong capsules.