Licorice (Glycyrrhizae radix et Rhizoma), one of the oldest and most frequently employed
folk medicine in Asia and Europe, is widely used to treat diseases of the respiratory
tract, gastrointestinal and cardiovascular system. A large number of metabolites have
been isolated from licorice, including triterpene saponins, glycyrrhizic acid is normally
being considered to be the main biologically active component. But liquiritin, liquiritigenin,
isoliquiritigenin, isoliquiritin and glycyrrhetinic acid have proved to possess various
activities. Licorice should contain at least 0.7% of liquiritigenin (C15H12O4: 256.27, LQ) and 2.5% or more of glycyrrhizic acid (C42H62016: 822.93, GA) as marker compounds in the Korea Pharmacopoeia (KP), for which the current
KP methods are reflux extraction for LQ (2 M HCl/90oC/1 hr and CH2Cl2/40oC/0.5 hr) and ultrasonic extraction for GA (70% EtOH, 1 hr, 2 times), respectively.
This work aimed at providing an alternative method for the fast simultaneous extraction
of both quality index constituents, LQ and GA for their HPLC determinations [1]. Microwave-assisted
extraction (MAE), which was operated at 150 W for 4 min using 0.5 g of liquorice root
powder (less than 5% in moisture, 80 mesh) and 50 mL of different solvents (70% &
100% EtOH, 70% & 100% MeOH, D.W.), was employed to compare its efficacy to that of
the conventional KP method, respectively [2, 3]. The results indicated that MAE was
more efficient than KP with reduction in extraction time from hours to min [4], as
well as simultaneous extraction of both marker compounds with concentrations higher
than standard limits of ≥0.7% in LQ and ≥0.25% in GA, respectively when using 100%
MeOH solvent.
Fig. 1: HPLC Chromatograms on Liquiritigenin and Glycyrrhizic acid from Licorice powder with
different solvents in microwave-assisted extraction (MAE) over conventional method
(KP)
Keywords: Liquorice (Glycyrrhizae radix et Rhizoma), liquiritigenin, glycyrrhizic acid, microwave
extraction, HPLC.
References:
[1] Pan X, Liu H, Jia G, Shu YY. Microwave-assisted extraction of glycytthizic acid from licorice root. Biochem Eng
J 2000; 5: 173 – 177
[2] Korea Food and Drug Administration. Korea Pharmacopoeia. Shinil Books Company,
2008
[3] Zhang QY, Ye M. Chemical analysis of the Chinese herbal medicine Gan-Cao (licorice). J Chromatogr
A 2009; 1216: 1954 – 1969
[4] Kwon JH, Bélanger JMR, Paré JJ, Yaylayan VA. Application of microwave-assisted process (MAP) to the fast extraction of ginseng
saponins. Food Res Int 2003; 36: 491 – 498