Abstract: A high performance liquid chromatographic method was developed to determine the content of cinnamic acid in rabbit plasma and the method was utilized for the study of pharmacokinetics. Cinnamic acid was separated by employing a column of Kromasil C18 (250 mm×4.6 mm i.d., 5 μm) and a mobile phase of methanol-acetonitrile-water-glacial acetic acid (10∶22∶55∶0.5, v/v) at a flow rate of 0.8 mL/min and room temperature with UV detection at 270 nm and phenylpropionic acid as internal standard. The extraction recoveries of the spiked samples at low, middle and high levels were 84.9%, 84.4%and 87.7%, respectively, while the method recoveries were 98.4% with relative standard deviation (RSD) of 5.5%, 99.2% with RSD of 3.6%, 100.1% with RSD of 3.7% in turn. The RSDs of intra-day and inter-day were both lower than 6%. Finally, the metabolism of cinnamic acid in rabbit plasma after medication of Guanxin Suhe Wan and Guanxin Suhe Capsule fitted in a first order absorption of two-compartment model. The method was found to be sensitive, accurate and precise, and is appropriate for the determination of cinnamic acid.

Key words: Guanxin Suhe , cinnamic acid, pharmacokinetics, high performance liquid chromatography