Purification of Phytochemicals by Gas Antisolvent Precipitation with Carbon Dioxide

Gas antisolvent precipitation (GAP) using dense carbon dioxide (CO2) is a novel technique for the purification or enrichment of phytochemicals by selective crystallisation. It involves dissolution of sub-critical CO2 into an organic solution of the extract for selectively reducing the solubility of the solid solutes of interest by antisolvent effect. The recovery and enrichment of three bioactive phytochemicals, such as beta-carotene, alpha-hydroxycitric acid, and licochalcone-A have been investigated in this paper. Initially, organic solvent (Soxhlet) extraction or supercritical CO2 extraction has been carried out for the recovery of beta-carotene from mango leaves, alpha-hydroxycitric acid from kokum, and licochalcone-A from licorice. Subsequently, purification has been performed by the GAP process using CO2 in the pressure range of 40 to 70 bar at 298 K, followed by filtration at the same pressure and temperature, and removal of the residual solvent from the product by flushing it with CO2. High performance liquid chromatography (HPLC) analysis of the phytochemicals before and after the GAP process confirms significant enrichment of the active ingredients.