Extraction of Volatile Oils from Asarum Heterotropoides by Supercritical CO_2 and Microwave-aided Techniques

The volatile oils were obtained with the supercritical CO2 and microwave methods to search for the optimum extraction conditions. The uniform design of experiment was used to optimize the supercritical CO2 extraction conditions. The optimal conditions were determined: pressure 16 MPa, temperature 32oC, CO2 flow rate 20 kg/h and time 80 min. The optimum conditions of the microwave extraction were obtained by orthogonal experiment: radiation time 200 s, microwave power 720 W, volume of solvent 300 ml, volume of washing solvent 30 ml. The volatile oils were obtained by supercritical CO2, microwave and steam distillation, and the extraction rate was 3.78%, 5.46% and 1.62% respectively. The results showed that the extraction rate of microwave extraction was higher and its process was simpler, but the quality of the volatile oil was worse than those extracted by supercritical CO2 and steam distillation.