Superheated water extraction of glycyrrhizic acid from licorice root

Superheated water extraction (SWE) has become an interesting green extraction method for different classes of compounds. In this study, SWE was used to extract glycyrrhizic acid (GA) from licorice root. Response surface methodology (RSM) was applied to evaluate and optimize the extraction conditions. The influence of operating conditions such as water temperature (100, 120 and 140 °C) and solvent flow rates (1, 3 and 5 mL/min) were investigated at 0.5 mm mean particle size and 20 bar pressure. Separation and identification of the glycyrrhizic acid, as the main component, was carried out by the RP-HPLC method. The best operating conditions for the SWE of licorice were determined to be 100 °C temperature, 5 mL/min flow rate and 120 min extraction time. The results showed that the amount of the obtained GA was relatively higher using SWE (54.760 mg/g) than the Soxhlet method (28.760 mg/g) and ultrasonic extraction (18.240 mg/g).