Abstract:Objective: To study the adscription of plasma effective constituents of rat after oral administration of Gegen Qinlian decoction. Method: This study was performed by using HPLC UV to identify the chemical constituents of rat plasma samples obtained after oral administration of the whole and individual herbs of Gegen Qinlian decoction. A reversed phase Globalsil C18 column (46 mm×250 mm, 5 μm) was used. The mobile phase was composed of 20 mmol·L-1 ammonium acetate (adjusted to pH 45 by acetate acid) and acetonitrile with gradient elution. The flow rate was 10 mL·min-1 and the column maintained at room temperature. The detection wavelength was set at 270 nm. Result: The chromatographic analysis of the rat plasma obtained after oral administration of Gegen Qinlian decoction showed 31 compounds, fifteen of which were the original constituents contained in Gegen Qinlian decoction, thirteen of which were metabolites, while the other three only existed after oral administration of the Decoction. By comparison of the retention times of the unknown peaks with that of standard compounds and, by spiking method with the standard compounds, five peaks were identified as puerarin, baicalin, berberine, jatrorrhizine and palmatine. Conclusion: This HPLC UV method is simple and reliable in the analysis of the UV absorbing chemical constituents of rat plasma. The compounds absorbed into blood and its metabolites are the possible effective constituents of Gegen Qinlian decoction because they interact directly within the body. The results obtained in this investigation may provide useful information in the further understanding of the action mechanism of the individual and whole herbs in Gegen Qinlian decoction.