Abstract: Objective：To establish an LC-MS/MS assay for the simultaneous determination of rosmarinic acid, carnosic acid, chlorogenic acid and caffeic acid in rosemary leaves and to optimize conditions for the ultrasonic extraction of these components. Methods: The chromatographic separation was performed on an Agilent Eclipse XDB-C18 column (150 mm × 4.6 mm, 5 µm) using a mobile phase consisting of acetonitrile and 0.1% formic acid in water by gradient elution. The analyztes were monitored by ESI-MS/MS in the negative ion MRM mode. The effects of solvent type, solid/liquid ratio, ultrasonic treatment time, pH and acid type on the extraction of rosmarinic acid, carnosic acid, chlorogenic acid and caffeic acid were investigated. Results: Caffeic acid, chlorogenic acid, rosmarinic acid and carnosic acid showed a good linear relationship over the concentration ranges of 0.0005–0.5, 0.0005–0.5, 0.002–0.2 and 0.01–1 mg/mL, respectively. Under optimal extraction conditions, the contents of rosmarinic acid, carnosic acid, caffeic acid and chlorogenic acid were respectively, 4.07, 14.50, 2.92 mg/g  and 8.49 mg/g as determined by the LC-MS/MS assay. Conclusion: This array allows rapid, sensitive and simultaneous determination of osmarinic acid, carnosic acid, chlorogenic acid and caffeic acid in rosemary leaves. Their optimal extraction conditions have been established.

Key words: rosemary, LC-MS/MS, ultrasonic-assisted extraction, rosmarinic acid, carnosic acid, chlorogenic acid, caffeic acid