This study examined supercritical carbon dioxide and near critical fluid extractions of artemisinin from Artemisia annua L. by varying pressure from 1000 psig (7.00 MPa) to 4500 psig (31.13 MPa), temperature from 30 to 60 degrees C, and co-solvent addition ratio ranged from 0 to 22.56 wt.%. The investigations included the total yield of the extracts, the recovery and the purity of artemisinin, and then the growth inhibition of rat hepatic stellate cells. Experimental results showed that dry supercritical carbon dioxide extraction was favorable for obtaining high purity but low recovery of artemisinin. A pre-loaded and continuing addition of co-solvent was proved to be effective in enhancing the recovery of artemisinin for the extractions near critical region. Moreover, a two-factor and three-level response surface methodology (RSM) disclosed that carbon dioxide added with 16.25 wt.% of N-hexane, extracted at 2700 psig (18.72 MPa), 33 degrees C, and for a period of 1.5 h could obtain an optimal value of quick recovery and high purity of artemisinin. Finally, treatments with the samples extracted using supercritical carbon dioxide and near critical fluids led to a strong inhibition of cell growth in primary cultured rat hepatic stellate cells. (C) 2006 Elsevier B.V. All rights reserved.