Development and validation of a green and sustainable procedure for the preparation of Perilla frutescens extracts

A procedure combining supercritical CO2 and ultrasound-assisted (USC-CO2) extraction was developed to obtain rosmarinic acid (RA)-rich extracts from Perilla frutescens. Based on extraction yields and efficiencies, USC-CO2 was considered the best extraction method among the methods studied for obtaining RA from P. frutescens. The constant extraction rate period and the falling extraction rate period for USC-CO2 extraction of P. frutescens were 45 and 96 min long, respectively, and they were significantly shorter than those of traditional SC-CO2 (TSC-CO2) extraction. Furthermore, mass transfer coefficients were derived using the Sovová model for the fluid and solid phases from USC-CO2 extraction, with values of 9.752 × 10-3 and 4.203 × 10-3 min-1, respectively, which were obviously higher than those for TSC-CO2 extraction. Consequently, the theoretical solubilities of RA in the supercritical solvents used in dynamic USC-CO2 and TSC-CO2 extractions were estimated and found to be well correlated using three density-based models.