In vitro antiviral activity of indigenous glycyrrhizin, licorice and glycyrrhizic acid (Sigma) on Japanese encephalitis virus.

Glycyrrhizin, a triterpenoid glycoside and Licorice from Glycyrrhiza glabra and Ammonium salt of Glycyrrhizic acid (Sigma) were tested for antiviral activity on three strains of Japanese encephalitis virus (JEV), Nakayama, P-20778 and 821564 XY48. Purified glycyrrhizin (M.w. 822.92) inhibited plaque formation in all the three strains of JEV at a concentration of 500 micrograms/ml at 96 hrs, Similar effect was observed at 1000 micrograms/ml concentration with Licorice and Ammonium salt of glycyrrhizic acid. The minimal inhibitory concentrations were not toxic to porcine stable kidney (PS) and human cervical carcinoma (HeLa) cell lines. Cyctotoxicity of these chemicals was evaluated by trypan blue dye exclusion test which indicated subtoxic concentrations at 5,000 micrograms/ml at 96 hrs and toxic concentrations were 10,000 micrograms/ml at the same time period for the host cells PS. Thus the indigenously purified glycyrrhizin seems to be more potent antiviral agent than Licorice and ammonium salt of glycyrrhizic acid (Sigma) for JEV 'in vitro'.