Scientists have isolated two substances in licorice root (glycyrrhiza uralensis), one of the most commonly used herbs in traditional Chinese medicine (TCM), that kill the major bacteria responsible for tooth decay and gingivitis in children and adults.

Known as Gan Cao in TCM, licorice root is commonly used in classical TCM formulas to harmonize and/or moderate harsh or adverse effects of other herbs, thereby protecting the Stomach and Spleen organ systems. However on its own the chemical structure of licorice root has demonstrated a large range of pharmacological effects, including glucocorticoid, anti-inflammatory, antiarrhythmic, immunologic, gastrointestinal, antispasmodic, antitoxin, hepatoprotective, antitussive, expectorant, analgesic, antibiotic, and antihyperlipidemic effects. As a result, clinical studies have shown that the use of licorice root by itself or in combination with other TCM herbs is effective in treating endocrine dysfunction, Addison's disease, peptic ulcer, tuberculosis, hepatitis, arrhythmia, back and leg pain, purpura, intestinal spasms, food poisoning, mushroom poisoning, tonsilitis, phlebitis, and acute mastitis.

Now the Journal of Natural Products has reported that scientists have identified that two of the compounds in licorice root, licoricidin and licorisoflavan A, were effective as antibacterial substances. These substances killed two of the major bacteria responsible for dental cavities (streptococcus mutans and streptococcus sobrinus), as well as two of the bacteria that promote gum disease (porphyromonas gingivalis and prevotella intermedia). Licoricidin also inhibited the growth of a third gum disease bacterium, fusobacterium nucleatum, although only moderately.

(Isoflavonoids and Coumarins from Glycyrrhiza uralensis: Antibacterial Activity against Oral Pathogens and Conversion of Isoflavans into Isoflavan-Quinones during Purification. J. Nat. Prod., 2011, 74 (12), pp 2514–2519. DOI: 10.1021/np2004775 Publication Date (Web): November 10, 2011. Copyright © 2011 The American Chemical Society and American Society of Pharmacognosy)