Liquorice (Glycyrrhiza glabra)

Traditional Indications

Liquorice is alterative, anti-inflammatory, antispasmodic, demulcent, diuretic, emollient, expectorant, laxative, pectoral, and tonic. It is a very sweet, moist, soothing herb that detoxifies and protects the liver and is also powerfully anti-inflammatory, being used in conditions as varied as arthritis and mouth ulcers. Liquorice root is much used in cough medicines and also in the treatment of catarrhal infections of the urinary tract. It is taken internally in the treatment of Addison's disease, asthma, bronchitis, coughs, peptic ulcers, gastric and duodenal ulcers, arthritis, allergic complaints and following steroidal therapy (1).

In TCM Liquorice is called Gān Căo甘草. Gān Căo is sweet, neutral and warm and enters all 12 channels but mainly the Heart, Lung, Spleen and Stomach. Liquorice tonifies the Spleen & Stomach Qi and is used to treat digestive disorders, moisten the lungs and stops dry cough, tonifies the Heart Qi to regulates pulse, clears Heat & Toxic Fire, alleviates pain, stops spasms, harmonise & moderates the characteristics of other herbs and is an antidote for toxicity. It should be used in moderation and should not be prescribed for pregnant women or people with high blood pressure, kidney disease or taking digoxin-based medication. Prolonged usage raises the blood pressure and causes water retention (2).

Pharmacognosy

More than 20 triterpenoids and nearly 300 flavonoids have been isolated from liquorice many of which possess antiviral and antimicrobial activities (3). The constituents, glycyrrhizin and glycyrrhetinic acid, inhibit 11-beta-hydroxysteroid dehydrogenase . This inhibition blocks metabolism of prostaglandins E and F2 alpha and may be responsible for peptic ulcer healing (4). Liquorice extract, 3 triterpenes and 13 flavonoids exhibit evident anti-inflammatory properties mainly by decreasing TNF, MMPs, PGE2 and free radicals (5).

Gan Cao Glycyrrhiza uralensis is part of a Chinese herbal formula called Shi Quan Da Bu Tang, traditionally used to tonify the Blood and Qi to treat anaemia, anorexia, extreme exhaustion, fatigue, kidney and spleen insufficiency and general weakness, particularly after illness and after chemotherapy. It has been found to potentiate (make it work better) chemotherapy and radiotherapy and inhibit malignant recurrences, prolong survival and prevent and ameliorate adverse toxicities in cancer treatment (6). In Japanese herbal medicine (Kampo) the formula is known Juzen Taiho To and has been shown to increase expression of heavy metal chelating metallothioneins (MTs) (7). Shi Quan Da Bu Tang also increases transcription factor Nrf2 to support phase II detoxification thus regulate the body's detoxification and antioxidant system (8).

The general antiviral activity of liquorice has been shown to help combat SARS-CoV-2 infection. The phytotherapeutic properties of liquorice (Glycyrrhiza glabra) extract are mainly attributed to glycyrrhizin (GR) and glycyrrhetinic acid (GA). Glycyrrhizin effectively inhibits SARS-CoV-2 replication. Among their possible pharmacological actions, the ability to act against viruses belonging to different families, including SARS coronavirus, is particularly important. In silico docking studies reported that GR and GA may directly interact with the key players in viral internalization and replication such as angiotensin-converting enzyme 2 (ACE2), spike protein, the host TMPRSS2 (transmembrane serine protease 2), and 3CLpro/Mpro) (9, 10).

1. PFAF. Glycyrrhiza glabra. 2019.
2. Lotus S. Gan Cao (Licorice Root). 2019.
3. Wang L, Yang R, Yuan B, Liu Y, Liu C. The antiviral and antimicrobial activities of licorice, a widely-used Chinese herb. Acta pharmaceutica Sinica B. 2015;5(4):310-5.
4. Whorwood CB, Sheppard MC, Stewart PM. Licorice inhibits 11 beta-hydroxysteroid dehydrogenase messenger ribonucleic acid levels and potentiates glucocorticoid hormone action. Endocrinology. 1993;132(6):2287-92.
5. Yang R, Yuan B-C, Ma Y-S, Zhou S, Liu Y. The anti-inflammatory activity of licorice, a widely used Chinese herb. Pharmaceutical biology. 2017;55(1):5-18.
6. Chang I-M. Juzen-taiho-to (Shi-Quan-Da-Bu-Tang): Scientific Evaluation and Clinical Application. Evidence-based Complementary and Alternative Medicine. 2006;3(3):393-4.
7. Anjiki N, Hoshino R, Ohnishi Y, Hioki K, Irie Y, Ishige A, et al. A kampo formula Juzen-taiho-to induces expression of metallothioneins in mice. 2005;19(10):915-7.
8. Wu Q, Zhang D, Tao N, Zhu QN, Jin T, Shi JS, et al. Induction of Nrf2 and metallothionein as a common mechanism of hepatoprotective medicinal herbs. Am J Chin Med. 2014;42(1):207-21.
9. Diomede L, Beeg M, Gamba A, Fumagalli O, Gobbi M, Salmona M. Can Antiviral Activity of Licorice Help Fight COVID-19 Infection? Biomolecules. 2021;11(6).
10. van de Sand L, Bormann M, Alt M, Schipper L, Heilingloh CS, Steinmann E, et al. Glycyrrhizin Effectively Inhibits SARS-CoV-2 Replication by Inhibiting the Viral Main Protease. Viruses. 2021;13(4).