Licorice, Glycyrrhiza glabra L., originates from Southeastern Europe and Western Asia. In herbal medicine, its roots are used for their medicinal properties. Its name comes from the Greek glukos, "sweet" and rhidza, "root".
Over time, it has received different names: sweet wood, licorice root or licorice stick. It is part of the Fabaceae family. The stem bears alternate leaves. The lila-colored flowers give rise to fruits which are small pods.
The therapeutic benefits of Licorice have been known since ancient times to treat asthma and ulcers. Licorice extracts are used for food purposes (for example in candy making and as flavoring agents in carbonated drinks), but can also be used to produce bioenergy (HASAN & al., 2021).
Its chemical composition is very rich: it contains in particular alkaloids, triterpene saponosides, mainly glycyrrhizin, flavonoids and isoflavonoids, as well as polysaccharides (WAN & al., 2009).
Licorice reduces ulcers induced by hydrochloric acid, ethanol and indomethacin in mice. Licorice extract delivered at 200 mg/kg is more potent than omeprazole (a proton pump inhibitor that reduces acid secretion in the stomach) given at 30 mg/kg. It decreases the ulcer index in mice with gastric ulcers induced by hypothermic stress. The antiulcer effect is comparable to that of cimetidine, an antihistamine indicated for the treatment of peptic ulcer disease and gastroesophageal reflux disease in men. This anti-ulcerogenic effect is associated with an increase in defensive factors of the gastric mucosa (JALILZADEH-AMIN & al., 2015). In addition, the polysaccharides it contains inhibit the adhesion of Helicobacter pylori to the stomach lining, thus potentially limiting the occurrence of gastric ulcers (WITTSCHIER & al., 2009).
Glycyrrhyzine, its major constituent, is responsible in particular for its hepato-protective action (WAN & al., 2009).
The glycyrrhizin contained in licorice exhibits anti-inflammatory activity which is partly conferred by its inhibiting effect on the prostaglandin E2 production (OHUCHI & al., 1981).
Licorice has antiviral properties (FIORE & al., 2008). It reduces hepatocellular damage in chronic viral hepatitis B and C and the risk of hepatocellular carcinoma in hepatitis C virus-induced cirrhosis. In addition, it decreases mortality and viral activity in viral encephalitis herpes simplex and influenza A pneumonia. It also has in vitro antiviral activity against HIV-1, SARS-related coronavirus, respiratory syncytial virus, arboviruses, vaccinia virus and vesicular stomatitis virus. The mechanisms of licorice antiviral effect include reduction of membrane transport and sialylation of the hepatitis B virus surface antigen, reduction of membrane fluidity leading to inhibition of fusion of the viral membrane of HIV-1 with the cell, induction of interferon gamma in T cells, inhibition of phosphorylating enzymes in vesicular stomatitis virus infection, reduction of viral replication and reduction of viral latency (CINATL & al., 2003 ; HOEVER & al., 2005 ; FIORE & al., 2008).
The polysaccharides in Licorice increase phagocytosis of macrophages, induce interleukin-1 secretion by macrophages, stimulate antibody-dependent cell-mediated cytotoxic activities. Through their activity on Natural Killer (NK) cells, they stimulate the production of B lymphocytes, inhibit viral multiplication and induce the release of interferons from spleen cells (YANG & YU, 1990).
The glycoumarin contained in Licorice inhibits the contraction of the jejunum of mice induced by various types of stimulants, with a potency similar to that of papaverine, an antispasmodic agent. This antispasmodic effect is mediated via inhibition of phosphodiesterases, in particular isozyme 3, followed by accumulation of intracellular cAMP (SATO & al., 2006). Liquorice rhizome alcoholic extract has been shown to reduce the force of contraction of the duodenum independently of the cholinergic, beta-adrenergic and NO pathways (KHOSHNAZAR & NAJAFIPOUR, 2013).
Licorice extract generated significant antidepressant effects in mice during the forced swim test and the tail hang test. Its efficacy has been shown to be comparable to that of imipramine and fluoxetine. The authors suggest that Licorice interacts with α1-adrenergic receptors and dopamine D2 receptors, increasing the levels of norepinephrine and dopamine in the brains of mice, but without effect on the serotonergic system (DHINGRA & SHARMA, 2006).
In addition, Licorice extract limits depression induced by reserpine, a molecule that produces significant depression by depleting biogenic amines in the brain. This antidepressant effect is associated with the restoration of brain monoamines, such as norepinephrine and dopamine (PASTORINO & al., 2018).
Glycyrrhizin taken in large amounts has effects similar to those of aldosterone. This hormone can cause fluid to be retained in the tissues, raise blood pressure and contribute to the loss of potassium. Therefore, it is advisable not to consume too much Licorice.
