Development and characterization of a green procedure for apigenin extraction from Scutellaria barbata D. Don

This study compared the use of ultrasound-assisted supercritical CO₂ (USC-CO₂) extraction to obtain apigenin-rich extracts from Scutellaria barbata D. Don with that of conventional supercritical CO₂ (SC-CO₂) extraction and heat-reflux extraction (HRE), conducted in parallel. This green procedure yielded 20.1% and 31.6% more apigenin than conventional SC-CO₂ extraction and HRE, respectively. Moreover, the extraction time required by the USC-CO₂ procedure, which used milder conditions, was approximately 1.9 times and 2.4 times shorter than that required by conventional SC-CO₂ extraction and HRE, respectively. Furthermore, the theoretical solubility of apigenin in the supercritical fluid system was obtained from the USC-CO₂ dynamic extraction curves and was in good agreement with the calculated values for the three empirical density-based models. The second-order kinetics model was further applied to evaluate the kinetics of USC-CO₂ extraction. The results demonstrated that the selected model allowed the evaluation of the extraction rate and extent of USC-CO₂ extraction.