Extraction of nobiletin and tangeretin from Citrus depressa Hayata by supercritical carbon dioxide with ethanol as modifier

An optimal condition of supercritical fluid extraction for two polymethoxyflavones (PMFs), nobiletin and tangeretin, from Citrus depressa Hayata was developed. The effect of modifier type, modifier composition in terms of water content in ethanol, modifier percentage, extraction condition (temperature, pressure and CO2 flow rate), and particle size on the yield of nobiletin and tangeretin were investigated. The contents of nobiletin and tangeretin were determined by HPLC. Results showed that the yield of nobiletin and tangeretin increased significantly with increased percentage of aqueous ethanol (85%) as a modifier in supercritical carbon dioxide up to 9.1%. The optimal temperature and pressure for selective supercritical fluid extraction (SFE) of nobiletin and tangeretin were 80 °C and 30 MPa, respectively. The extraction rate was increased by increasing CO2 flow rate. The optimal particle size of sample was found to be 0.375 mm. Overall, the nobiletin and tangeretin yield of SFE was 107% compared to conventional solvent extraction method (100%). Therefore, application of SFE for extraction of nobiletin and tangeretin from C. depressa Hayata peel was preferable.