Solvent extraction of podophyllotoxin was carried out with different ethanol-water solvent systems at various extraction conditions. Maximum extraction rate and yield were obtained with a solvent system of 30 ethanol/70 water (volumetric ratio) and 53 degrees C for all particle moisture contents. When temperature increased from 53 to 80 degrees C, the extraction yield of podophyllotoxin significantly decreased due to podophyllotoxin degradation. Particle moisture content had significant effect on yield only at 100% ethanol. Also radio frequency heating had no significant effect on yield and extraction rate within 30-55 degrees C. A diffusional mathematical model was developed and used to determine the effective diffusivity and partition coefficient of podophyllotoxin for 14 extraction conditions. A very good agreement between predictions and observations led to reliable estimations of the effective diffusivity and partition coefficient of podophyllotoxin. (C) 2008 Elsevier B.V. All rights reserved.