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.
Albu, S., Joyce, E., Paniwnyk, L., Lorimer, J. P., & Mason, T. J. (2004). Potential for the use of ultrasound in the extraction of antioxidants from Rosmarinus officinalis for the food and pharmaceutical industry. Ultrasonics Sonochemistry, 11(3-4), 261-265. https://doi.org/10.1016/j.ultsonch.2004.01.015