Semibatch flow extraction of oil and other active ingredients from some plant materials (Silybum marianum; pepper, paprika and cocoa) with supercritical fluids (SCF) such as CO2 and propane at different operating conditions was studied. Dynamic behaviour of the extraction runs was analysed by a mathematical model based on the adsorption-desorption equilibrium of extractable component from solid tissue, the diffusion of extractable component dissolved in SCF to the surface and mass transfer through the external film into the bulk, The linear driving force concept was employed to incorporate intraparticle diffusion as well as external mass transfer. Results show that the simplified model, which describes desorption process at equilibrium, could successfully describe cumulative rate data and is specially interesting fur observation of the cross-over effect for adsorption-desorption, i.e. how desorption is changed with the increase of temperature at constant pressure.