Hedyotis diffusa and Hedyotis corymbosa are the major ingredient of healthy teas commonly consumed in China for health maintenance. The objective of the present study was to evaluate the kinetics of a green process of ultrasound-assisted supercritical carbon dioxide (USC-CO2) extraction for determining the content of oleanolic acid (OA) and ursolic acid (UA) in both herbs. The results elucidated various advantages of USC-CO2 extraction, which can significantly increase extraction yields and reduce the extraction time and solvent consumption at lower operational conditions than the conventional SC-CO2 and solvent extraction methods. The combined USC-CO2-HPLC method was further applied to extract and quantitate the OA and UA contents in samples obtained from different geographical regions. The experimental results obtained indicate that H. diffusa and H. corymbosa were a suitable source for OA and UA production and the OA and UA content in the samples from different sources were significantly different. Furthermore, the kinetics of USC-CO2 extraction was determined based on a second-order kinetic model. The activation energies of OA and UA were 6.784 and 4.981 kJ/mol, respectively. (C) 2015 Elsevier B.V. All rights reserved.