Six bioactive flavonoids were isolated from Scutellaria barbata D. Don through heat-reflux, ultrasound-assisted, conventional supercritical CO2 and ultrasound-assisted supercritical CO2 (USC-CO2) extractions using different extraction schemes and parameters. The USC-CO2 extraction method produced higher yields of six flavonoids that were 28.09-29.31, 24.64-27.74 and 18.63-19.03% higher than those of heat-reflux, ultrasound-assisted and conventional supercritical CO2 extractions, respectively, with time durations that were lower by factors of 2.29, 1.14 and 2 than those of the three other extraction techniques and with less-harsh operating conditions. Therefore, the current procedure is a promising technique for the extraction of various bioactive constituents from a wide variety of raw matrixes. Furthermore, a second-order kinetic model and a mass transfer model based on Fick's second law were successfully correlated with the overall USC-CO2 dynamic extraction of S. barbata D. Don. The results obtained from the second-order kinetic model indicated that the energy barrier in the USC-CO2 procedure was lower than that in the traditional extraction techniques. In addition, the mass transfer model revealed that incrementing the operation temperature from 32 to 52 degrees C at constant pressure might effectively enhance the mass transfer and diffusion in the current procedure and that the current procedure is dominated by intraparticle diffusion. These results provide very helpful information for the design and development of an efficient procedure to extract bioactive flavonoids from a wide variety of matrixes for future applications in industrial extraction processes.
