Antibacterial compounds of licorice against upper airway respiratory tract pathogens.

The antibacterial activity of compounds obtained from licorice was measured against upper airway respiratory tract bacteria such as Streptococcus pyogenes, Haemophilus influenzae and Moraxella catarrhalis. Among the tested compounds, licoricidin exhibited the highest activity against all tested microorganisms with an MIC of 12.5 microg/mL. Three coumarin derivatives, glycyrol, glycyrin and glycycoumarin also showed antibacterial activity.