Ultrasound was used to increase the extraction efficiency of carnosic acid from the herb Rosmarinus officinalis using butanone, ethyl acetate and ethanol as solvents. Both dried and fresh leaves of the herb were extracted and, when performed at the same temperature, sonication improved the yields of carnosic acid for all three solvents and shortened the extraction times. Sonication also reduced the solvent effect so that ethanol, which is a poor solvent under conventional conditions, reached a similar level of extraction efficiency to the other two when sonicated. The extraction of dried herb with ethanol proved to be more efficient than that of fresh material, probably due to the water present in the latter.

The aim of this study was to examine the effect of ultrasound on the solvent extraction of anti-oxidants from the rosemary herb and to scale up the ultrasonic extraction process. The anti-oxidants of interest were identified using HPLC. Results indicated that, compared with conventional solvent extraction, the use of ultrasound gives a more effective extraction at lower temperatures with less dependence on the extraction solvent employed and that scale up of the process is possible.