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

•Oleanolic acid (OA), ursolic acid (UA) and oridonin were extracted from Rabdosia rubescens.•A second-order kinetic models for HUAE of OA, UA and oridonin were analyzed.•The activation energies for HUAE were determined using the Arrhenius model.•HUAE process achieves better yields while saving time, solvent, energy and raw materials.•HUAE is an efficient and environmentally friendly technique for food industries.

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.

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