Supercritical fluid extraction of paeonol from Cynanchum paniculatum (Bge.) Kitag. and subsequent isolation by high-speed counter-current chromatography coupled with high-performance liquid chromatography-photodiode array detector

Supercritical fluid extraction (SFE) was used to extract paeonol from Cynanchum paniculatum (Bge.) Kitag. The extraction conditions including pressure, temperature, time and sample particle size were optimized with an orthogonal test. Under the optimized conditions of 15 MPa, 55 °C, 1.5 h and a sample particle size of 40–60 mesh, the process was repeated 10 times, and the extract was then collected. The yield of the crude extract from preparative SFE was 6.02%, which contained paeonol 72.02%. Paeonol of crude extract obtained by SFE, Ultrasonic Extraction (UE), Microwave-Assisted (MA), Steam Distillation (SD) and Soxhlet Extraction (SE) were further analyzed by HPLC-PDA to compare the extraction methods, and SFE is considered as the optimum one among the five processes. The SFE extract obtained was then purified successfully by high-speed counter-current chromatography (HSCCC) with a two-phase solvent system composed of petroleum ether–ethyl acetate–methanol–water (2:6:3:4, v/v) in one-step separation. From 2.42 g of the crude extract, 1.07 g of paeonol was obtained at 99.4% purity as determined by HPLC-PDA. These results indicate that SFE and HSCCC are very powerful techniques for the extraction and purification of paeonol from C. paniculatum.