Extraction of nimbin from neem seeds using supercritical CO2 and a supercritical CO2-methanol mixture

Nimbin, a component found in neem seeds, which is reported to have several valuable medicinal properties including: anti-inflammatory, anti-pyretic, anti-fugal, antihistamine and antiseptic was extracted from neem seeds using supercritical CO2 and CO2 with a methanol modifier. Nimbin extraction yields using supercritical carbon dioxide were found to be approximately 85% at 308 K, 23 MPa and a CO2 flow rate of 0.62 cm(3)/min for a 2-g sample of neem. An optimum extraction pressure appears to exist at approximate to23 MPa and 328 K. Although extraction using a methanol modifier did improve the extraction somewhat, methanol was not found to be an effective modifier for extracting nimbin. Dynamic extraction curves were predicted using three empirical models and a theoretical model. The three empirical models were: a Langmuir gas adsorption model, a first order plus dead time (FOPDT) model and a so-called t" cyclone model used to incorporate sigmoidal curves. The parameters in the empirical models were fitted to the experimental data. The Goto et al. [J. Chem. Eng. Jpn. 31 (1998) 171] theoretical model was compared to the experimental results and was found to fit the data well. The theoretical model shows that the extraction yield depends strongly on the solvent flow rate, that is, external mass transfer or equilibrium is the controlling step of this process. (C) 2003 Elsevier B.V. All rights reserved.