Optimization of ultrasound-assisted extraction of glycyrrhizic acid from licorice using response surface methodology

The present study optimized ultrasound-assisted extraction conditions to maximize extraction yields of glycyrrhizic acid from licorice.

The optimal extraction temperature (X₁), extraction time (X₂), and methanol concentration (X₃) were identified using response surface methodology (RSM). A central composite design (CCD) was used for experimental design and analysis of the results to obtain the optimal processing parameters.

Statistical analyses revealed that three variables and the quadratic of X₁, X₂, and X₃ had significant effects on the yields and were followed by significant interaction effects between the variables of X₂ and X₃ (p < 0.01). A 3D response surface plot and contour plots derived from the mathematical models were applied to determine the optimal conditions. The optimum ultrasound-assisted extraction conditions were as follows: extraction temperature, 69 °C; extraction time, 34 min; and methanol concentration, 57%. Under these conditions, the experimental yield of glycyrrhizic acid was 3.414%, which agreed closely with the predicted value (3.406%).

The experimental values agreed with those predicted by RSM models, thus indicating the suitability of the model employed and the success of RSM in optimizing the extraction conditions.