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 50μm 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 β-carotene, α-carotene, nobiletin and tangeletin were estimated by solubility being treated as a single fitting parameter in the dynamic extraction model. Solubility of β-carotene nearly corresponds with the value in literature (1O^-8∼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 β-carotene and solubilities of nobiletin and tangeletin were estimated to be double-digit higher, from 10^-6 to 10^-5 in the experimental conditions.