Comparison of techniques for extraction of isoflavones from the root of Radix Puerariae: Ultrasonic and pressurized solvent extractions

Radix Puerariae (RP), a traditional Chinese medicinal herb, has been used for a variety of disease prevention and treatment purposes. Three isoflavones, puerarin, daidzin and daidzein, isolated from RP are responsible for its broad therapeutic effects. In the present study, we demonstrate the application of three extraction methods, traditional, pressurized solvent extraction (PSE) and ultrasonic techniques, for preparing ethanolic RP extract. A comparison of the three extraction methods showed preferential higher yields of the three major isoflavones when the ultrasonic technique was applied. The extraction yield became higher as the mean size of RP particles decreased while the total accumulated power varied from 20 to 80 MJ at the solid-to-solvent ratios of 1:5 and 1:10 (g/ml). The relationship among accumulated energies, extraction yields and mean particle sizes under different extraction ratios using ultrasound was also discussed. This study proves that using the ultrasonic method should be the most economic way for enhancing the extraction yield of isoflavones-containing herbal extract in a short time with a reduced amount of solvent at a lower temperature. 2006 Elsevier Ltd. All rights reserved.