Kinetic and characterization studies for three bioactive compounds extracted from Rabdosia rubescens using ultrasound

Rabdosia rubescens is a well-known herbal tea in China with many health benefits. In this study, a hyphenated procedure involving heat-reflux and ultrasound-assisted extraction (HUAE) was developed to extract oleanolic acid (OA), ursolic acid (UA) and oridonin from R. rubescens. The effects of various parameters on the extraction efficiencies for these components were evaluated. Furthermore, the extraction kinetics were described and the activation energies for the three compounds of interest were derived based on the Arrhenius model. Under the optimized extraction conditions, the HUAE process extracted OA, UA and oridonin (0.54 +/- 0.02, 2.05 +/- 0.08 and 7.95 +/- 0.27 mg/g, respectively) from R. rubescens in higher yields than either technique alone. The activation energies for the OA, UA and oridonin extractions were -12.355, -13.880 and -7.166 kJ/mol, respectively. It was concluded that HUAE extractions follow second-order kinetics. HUAE technique is an efficient and environmentally benign process for use by the food and pharmaceutical industries. (C) 2015 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.