Simultaneous Determination of Six Phenolic Constituents of Danshen Injection in Rat Plasma by Liquid Chromatography—Electrospray Ionization—Mass Spectrometry and its Application to a Pharmacokinetic Study

Salvianolic acid A, salvianolic acid B, danshensu, protocatechuic aldehyde, rosmarinic acid and lithospermic acid are the six major active constituents in Danshen injection. In this study, a rapid, sensitive and specific liquid chromatographic–electrospray ionization–mass spectrometry method for the simultaneous quantitative determination of these compounds in rat plasma was developed. After a single step of liquid–liquid extraction with ethyl acetate, they were eluted by a Hypersil C₁₈ column (5 μm, i.d. 4.6 × 200 mm) within 4 min with a mobile phase consisting of acetonitrile and 0.1% formic acid water solution (35:65, v/v). The assay was linear in the concentration range of 0.05–10 μg mL⁻¹. Absolute recoveries were above 60%. The precisions and accuracies determined within three consecutive days were within acceptable limits. The method was successfully applied to a pharmacokinetic study in rats after an intravenous administration of Danshen injection.