Solubility Estimation of High-value Natural Products in Supercritical CO2 Using a Dynamic Extraction Model

Supercritical CO2 extraction was carried out using finely-milled powder of Unshu Citrus peels with approximately 50 mu m at 333 and 353 K and at CO2 densities of 600,700 and 800 kg m(-3). Extracts were analyzed by HPLC. Polymethoxyflavones and carotenes were detected but chlorophylls were not detected in each experimental condition. A dynamic extraction model was applied to the obtained data using solubility as a parameter and extraction curves of solutes in the peels were produced successfully. Solubilities of beta-carotene, alpha-carotene, nobiletin and tangeletin were estimated by solubility being treated as a single fitting parameter in the dynamic extraction model. Solubility of beta-carotene nearly corresponds with the value in literature (10(-8)similar to 10(-7)) and this showed the technique of estimation would be feasible for materials being unavailable. Solubility of a-carotene was found to be very close to that of beta-carotene and solubilities of nobiletin and tangeletin were estimated to be double-digit higher, from 10(-6)to 10(-5) in the experimental conditions.