Preparation of High-quality Glabridin Extract from Glycyrrhiza glabra

Supercritical fluid extraction (SFE) using cosolvent-modified supercritical carbon dioxide and a two-step separation/purification method was investigated as a way to improve the purity of glabridin, one of the many bioactive components of Glycyrrhiza glabra (licorice). The SFE parameters were optimized using an analytical-scale SFE system in the temperature range 40–80°C and the pressure range 10–50 MPa. The extraction was then scaled up by 100 times using a preparative SFE system under the following set of optimized conditions: 40°C, 30 MPa, and SCCO₂ modified with ethanol equivalent to its 25% (v/v) concentration. The glabridin purity obtained through the scaled-up SFE system was 6.2%, a much higher level than that obtained through organic solvent extraction. The licorice extract obtained by scaling up the SFE system was isolated and purified by applying alcohol precipitation/ filtration and adsorption chromatography with 80% aqueous ethanol to obtain a purer product. It was confirmed that the glabridin purity of the final extract product was increased by up to 37%, without significant loss of glabridin after two separation/purification steps.