Glycyrrhizic acid inhibits influenza virus growth in embryonated eggs.

Glycyrrhizic acid, at doses well tolerated by the cells in monolayer cultures, inhibited the recovery of hemagglutinins from both Influenza and Newcastle Disease virus-infected embryonated hen eggs. Since the drug had no effect on viral viability and did not impair the hemagglutinating activity of the virions, the growth of viruses into the embryo tissues might be mainly affected. Late viral replication steps, rather than the early ones, appeared to be involved in the inhibitory effect of glycyrrhizic acid.