Glycyrrhizin increases survival of mice with herpes simplex encephalitis.

We examined the effect of glycyrrhizin (GR), a component of licorice root extract, on herpetic encephalitis that was inflicted on mice by inoculation of herpes simplex virus 1 (HSV-1) onto their cornea. Intraperitoneal (i.p.) administration of GR to mice suffering from herpetic encephalitis increased their survival rate in average about 2.5 times (from 37.5-29.0% to 81.8-83.3%; mean values from 2 experiments) while it reduced HSV-1 replication in the brain to 45.6% of the control. These results demonstrate a stimulative effect of GR on the mouse defense system(s) against HSV-1 infection.