Technology model with response surface methodology for supercritical CO₂ extraction and crystallization of andrographolide

The extract of Andrographis paniculata(Burm.f.) Nees(30% andrographolide) was used as experimental material, and the model of a second order quadratic equation for supercritical carbon dioxide extracting and crystallizing andrographolide was built by response surface methodology(RSM). The adequacy of the model equation for predicting the optimum response values was verified effectively by the validation. Effects of pressure, temperature and time on crystallization ratio were investigated. The optimized technology parameters were pressure of 20.88 MPa, temperature of 50.27℃, time of 97.02 min, and under these conditions the crystallization ratio of andrographolide was up to 74.77%.