In this work, supercritical carbon dioxide with ethanol as cosolvent was employed to extract bioactive compounds fromPolygonum Cuspidatum. Effect of temperature for 40 and 50 C on the extraction at 35 MPa was examined. It was found that extraction at 50 C resulted in high yield. A two-stage extraction at 50 C and 35 MPa was then designed to investigate effect of cosolvent on the recovery of resveratrol and emodin. The first stage extraction by solely using carbon dioxide can rarely extract resveratrol, but adding ethanol as cosolvent in the second stage significantly increases the extraction of resverarol and emodin. The crude extract obtained in the second stage was very stable against agglomeration and precipitation, because the first stage extraction helped to remove impurities from thePolygonum Cuspidatum. The stable crude extract was subsequently used as the feed for the SMB (simulated moving bed) separation. In this work, experimental validation was completed by solely using single SMB to isolate resveratrol, emodin, and physcion from the crude extract. As conducting the SMB experiments, the Triangle theory was used to help to determine the separable operating conditions. From the discussion of the experimental results, the criterion to obtain the pure resveratrol and physcion, and the concentrated emodin were depicted. Since both the extraction and the purification are conducted at low temperature, the bioactivity of the produced natural products will totally be preserved. The two-stage extraction and subsequent purification in this paper will provide greener and effective alternative for the development of botanical drugs.
Two-Stage Cooling Cycle with Expander Based on Carbon Dioxide