Medical Attributes of Glycyrrhiza glabra – Licorice

by John Treven, Steve Lehmkuhl, and Jonelle Vinton
Wilkes University, Wilke-Barre, PA

July 2005

Glycyrrhiza glabra, commonly called licorice, is a member of the Fabaceae (legume family).  G. glabra is native to the Mediterranean region and central and southwest Asia.  It was introduced to Europe in the fifteenth century where the roots became popular chewing sticks (Kowalchik & Hylton, 1987; Brown, 1995).  Two other commonly used relatives include Glycyrrhiza lepidota which is found throughout America and Glycyrrhiza uralensis which is found in northwest China (Foster, 2000).

G. glabra root was used during the time of the Roman Empire and was also found in the first Chinese herbal (Kowalchik & Hylton, 1987).  Hippocrates, Theophrastus, and Pliny where aware of the therapeutic value of the root and it was used to soothe throats and quench thirst.  Theophrastus mentioned it in his Inquiry into Plants for asthma and wound healing.  Today, licorice root is used to flavor and color beverages and is also used to flavor tobacco products. Medicinally, it has been used for treatment of dropsy; fever; menstrual cramps; menopause symptoms; irritated urinary, bowel, or respiratory passages; influenza; and hypoglycemia. It has also been used as a diuretic, demulcent, expectorant, emollient, antispasmodic, mild laxative, and cough remedy (Kowalchik & Hylton, 1987).

The most common medicinal use for licorice root is as a treatment for irritated skin with symptoms such as dermatitis, eczema, pruritus and cysts (Saeedi, Morteza-Semnani & Ghoreishi, 2003). G. glabra had remarkable effects against certain bacteria that cause acne, and greater results than erythromycin which is marketed for acne treatment (Nam, et al, 2003). Licorice root has also been used in the past as an expectorant, meaning it loosens and helps expel congestion in the upper respiratory tract (Foster, 2000). G. glabra has a history of being used to treat ulcers dating back to 1942. Current studies show it encourages mucus secretion and promotes life span of surface cells in the stomach. The combined effect of these leads to reduction of gastric ulcers (Foster, 2000).

The main ingredient in the root is a saponin like glycoside called glycyrrhizin.  It is more than fifty times sweeter than sugar and is used to enhance chocolate.  It has recently been identified as a selective inhibitor of thrombin. However, it does not inhibit the blood clotting action of thrombin meaning that the interaction is not very intense. The anti-inflammatory effect of glycyrrhizin may be due to its anti-thrombin properties (Francischetti, Monterio & Guimaraes, 1997).

Other medical uses of licorice root have been tested. As an anti-cancer agent, glycyrrhizin has shown to offer protection from cancerous damage produced by humans or UVB radiation, but not useful as a treatment for existing cancers (Rossi, et al 2005). Another experiment showed that the hydrophobic flavonoids of licorice root have abdominal fat lowering and hypoglycemic effects. (Nakagawa, Kishida, Arai, Nishiyama, Mae, 2004). Glycyrrhiza glabra was shown to have memory-strengthening activity in mice. In this same study it reversed the amnesia that was induced by diazepam in mice (Parle, Dhingra,  & Kulkarni, 2004).

G. glabra has several known adverse reactions to the glycerrhizic acid extract.  Some side effects noted were facial and dependent edema, headache, shortness of breath, stiffness and upper abdominal pain (Schambelean, 1994).  These side effects are, however, resolved with lower doses.

The most serious side effect shown from ingestion of glycyrrhizic acid is hyper-mineralcorticoidism which leads to hypertension.  The effect is believed to be entirely due to increased renal sodium retention.  Once ingested, the glycyrrhizic acid hydrolyzes in the body to form glycyrrhetinic acid, which inhibits a steroid metabolizing enzyme called 11 beta-HSD2 (Serra et al., 2001).  The low levels of this enzyme causes an increased access of cortisol to its receptors, leading to renal sodium retention and loss of potassium (Serra et al., 2001).

In a review of published reports on licorice, Stormer (1993) noted that “for the most sensitive individuals, a regular daily intake of no more than about 100 mg of glycyrrhizic acid seems to be enough to produce adverse effects.”  A dose of 10-12 mg/day was agreed to be a safe dose even for those sensitive to the extract (Stormer, 1993).

Patients who are diagnosed with hypertension are cautioned by their physicians to keep their blood pressure within acceptable limits.  Even in low doses, licorice root would be contraindicated for a patient who is diagnosed with hypertension due to an underlying disease, such as coronary artery disease, because of the effect glycyrrhizic acid on the body (Sigurjonsdottir, 2001).


Brown, D. 1995. The Herb National Society of America Encyclopedia of Herbs and Their Uses. Dorling Kindersley Publishing Inc. New York. p135.

Foster, S. 2000. Licorice. Stephen Foster Group (

Francischetti, I.M., R.Q. Monterio, & J.A. Guimaraes. 1997. Identification of glycyrrhizin as a thrombin inhibitor. Biochemistry  Biophysiology Res Commun 237 (1):203.

Kowalchik, C. & W.H. Hylton. 1987. Rodale’s Illustrated Encyclopedia of Herbs. Rodale Press. Pennsylvania. 360 –363pp

Nakagawa, K., H. Kishida, N. Arai, T. Nishiyama, & T. Mae. 2004. Licorice flavonoids suppress abdominal fat accumulation and increase in blood glucose level in obese diabetic KK-A(y) mice. Biol Pharm Bull. 27 (11):1775-1778

Nam, C., S. Kim, Y. Sim, & I. Chang. 2003 Anti-acne effects of Oriental herb extracts: a novel screening method to select anti-acne agents. Skin Pharmacology Applied Skin Phsiology 16 (2):84-90

Parle, M., D. Dhingra, & S.K. Kulkarni. 2004 Memory-strengthing activity of Glycyrrhiza glabra in exteroceptive and interoceptive behavioral models. Med Food 7 (4):462-466

Rossi, T., L. Benassi, C. Magnoni, A.I. Ruberto, A. Coppi, & G. Baggio. 2005. Effects of glycyrrhizin on UVB-irradiated melanoma cells. In Vivo 19 (1):319-22

Saeedi, M., K. Morteza-Semnani, M.R. Ghoreishi. 2003. The treatment of atopic dermatitis with licorice gel. J Dermatolog Treat. 14 (3):153-157

Schambelan, M.  1994.  Licorice ingestion and blood pressure regulating hormones.  Steroids 59 (2):127-130.

Serra, A, D.E. Uehlinger, P. Ferrari, B. Dick, B.M. Frey, F.J. Frey, & B. Vogt.  2002.  Glycyrrhetinic acid decreases plasma potassium concentrations in patients with anuria.  Journal of the American Society of Nephrologists 13 (1):191-196.

Sigurjonsdottir, H.A. L. Franzon, K. Manhem, J. Ragnarsson, G. Sigurdsson, and S. Wallerstedt
2001.  Liquorice-induced rise in blood pressure: a linear dose-response relationship.  Journal of Human Hypertension 15 (8):549-552.

Stormer, F.C., R. Reidstat, & J. Alexander.  1993.  Glycyrrhizic acid in liquorice-evaluation of health hazard.  Food Chemistry and Toxicology 31 (4):303-312.

This paper was developed as part of the BIO 368 - Medical Botany course offered at Wilkes University during the summer of 2005. Course instructor was Kenneth M. Klemow, Ph.D. ( The information contained herein is based on published sources, and is made available for academic purposes only. No warrantees, expressed or implied, are made about the medical usefulness or dangers associated with the plant species in question.

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This page posted and maintained by Kenneth M. Klemow, Ph.D., Biology Department, Wilkes University, Wilkes-Barre, PA 18766. (570) 408-4758,