Optimization of supercritical fluid extraction of saikosaponins from Bupleurum falcatum with orthogonal array design.

Supercritical fluid extraction (SFE) was used to extract saikosaponins a, c and d from the root of Bupleurum falcatum. An orthogonal array design L(9)(3)(4) was employed as a chemometric method for the optimization of the SFE conditions. The effects of four factors including pressure (30-40 MPa), temperature (40-50 degrees C), ethanol concentration (60-100%) and time (2.5-3.5 h) on the yields of saikosaponins were investigated by a preparative SFE system in the SFE mode. Under the optimized conditions, namely 35 MPa of pressure, 45 degrees C of temperature, 80% of ethanol concentration and 3.0 h of time, the yields of saikosaponin c, saikosaponin a, saikosaponin d, total saikosaponins and SFE extract were 0.16, 0.12, 0.96, 1.24 and 16.48 mg/g, respectively. Determinations of the saikosaponins were performed by HPLC.