Effects of modifiers on the supercritical CO2 extraction of glycyrrhizin from licorice and the morphology of licorice tissue after extraction

Optimal conditions for the supercritical carbon dioxide (scCO2) extraction of glycyrrhizin from licorice (Glycyrrhiza glabra) were investigated, with an emphasis on the types and levels of modifiers. The morphology of the licorice tissue remaining after the scCO2 extraction of glycyrrhizin was examined by scanning electron microscopy, coupled with measurements of absolute density. Conventional organic solvent extraction was also carried out for purpose of quantitative comparison. At 50 MPa and 60°C glycyrrhizin could not be extracted with pure scCO2, while a considerable amount of glycyrrhizin was extracted when water was added to scCO2 as a modifier. The highest recovery was found to be about 97% when 70% aqueous methanol was added to scCO2 at a concentration of 15%. The optimal pressure and temperature for the supercritical fluid extraction of glycyrrhizin were observed to be 30 MPa and 60°C, respectively. Under these conditions, the percentage recovery of glycyrrhizin attained a maximum value of 102.67±1.13% within 60 min. Furthermore, in the case of scCO2 modified with 70% aqueous methanol, the licorice tissue obtained after extraction was found to be severely degraded by excessive swelling, and the absolute density of the licorice residues was observed to be the highest.