Licorice

Licorice is a perennial herb 30–100 cm tall with a thick taproot and rhizome, light-brown bark and bright-yellow root flesh. Its odd-pinnate leaves bear 3–7 pairs of ovate leaflets with entire margins and sticky glandular dots beneath. Flowers sit in axillary racemes, bilaterally symmetrical (papilionaceous) and violet to deep purple; the plant flowers from June to August and forms curved pods with 2–8 seeds.

According to Kew POWO and World Flora Online, Glycyrrhiza uralensis is native to temperate Asia: northern and north-western China (Inner Mongolia, Xinjiang, Gansu, Ningxia, Qinghai), Mongolia, Central Asia (Kazakhstan, Kyrgyzstan, Tajikistan), southern Siberia, Afghanistan and Pakistan; it is introduced in Korea. The genus Glycyrrhiza holds about 20 species, five of which synthesise glycyrrhizin: G. uralensis, G. glabra, G. inflata, G. aspera and the North American G. lepidota.

The root contains more than 400 secondary metabolites, dominated by triterpenoid saponins with glycyrrhizin (glycyrrhizic acid) at 2–14% (typically 3–5%); in the gut it is hydrolysed to the aglycone 18β-glycyrrhetinic acid. Flavonoids include liquiritin, isoliquiritigenin and licochalcone, alongside polysaccharides, coumarins and phenolic acids. In 2025 a 415 Mbp reference genome of G. uralensis was published, opening the way for breeding and biotechnological production of glycyrrhizin.

In Chinese medicine licorice is called the 'national elder' for harmonising and potentiating other herbs; in the West the root has long flavoured confectionery, tobacco and beverages. Diammonium glycyrrhizinate is used to treat chronic hepatitis B and C. Modern studies show glycyrrhizin and 18β-glycyrrhetinic acid have antiviral activity (SARS-CoV-2, HSV, HBV, HCV, influenza), anti-inflammatory effects via NF-κB and MAPK inhibition, plus antioxidant and hepatoprotective actions; 2023 reviews synthesise this preclinical and clinical evidence.

High or prolonged licorice intake can cause pseudoaldosteronism: hypertension, hypokalaemia, oedema and fluid retention; it should be avoided in hypertension, kidney disease and pregnancy. The European Medicines Agency (EMA) limits glycyrrhizic acid intake to about 100 mg/day. The species is Not Evaluated (NE) by the IUCN, yet over-harvesting of wild roots in Central Asia and northern China has reduced populations; medicinal supply now comes mainly from cultivation, and the plant is also used to fix sand and curb desertification.