Anti-dengue viral activity of Glycyrrhiza glabra roots in Vero cells
Dengue is a global public health problem but no antiviral agent exists for dengue. Plants have been the source of many pharmaceutical agents. Therefore, we explored the antiviral potential of the aqueous extracts of Glycyrrhiza glabra (GG) roots on dengue viruses. Cell cytotoxicity assay with 3-(4, 5-dimethyl-2-thiazolyl)-2, 5-diphenyl-2H-tetrazolium bromide solution was used for estimating the maximum nontoxic dose (MNTD) and 50% cytotoxic concentration (CC50). Plaque reduction antiviral assay on Vero cells infected with dengue virus serotypes 1,2,3 and 4 were treated with dilutions of the MNTD of GG extract to calculate the half maximal inhibitory concentration (IC50). Selectivity index (SI) was calculated as CC50/IC50 ratio. Following bioactivity guided fractionation, MNTD, CC50, IC50 and SI values for fractions E and F were similarly obtained. Inhibition of NS1 antigen levels produced by dengue serotype-1 infected monocytes was studied in the presence and absence of GG extract after 48 hours. GG MNTD and CC50 were 166.7 {micro}g/mL and 651.9 {micro}g/mL. GG extract showed 98-100% inhibition of all four dengue serotypes at the MNTD and the IC50 values of the four serotypes ranged from 10-50 {micro}g/mL indicating moderate pan-serotype inhibitory activity. Cytotoxicity of GG against Vero cells was low (CC50 >500 {micro}g/mL). SI of GG extract for all four dengue serotypes were >10, indicating it had good potential as an antiviral agent. Fraction E and F had low to moderate inhibitory activity for all four serotypes and showed good potential as an antiviral agent only for dengue 4. This is the first report of significant anti-dengue viral activity of GG extract on all four dengue serotypes. Author SummaryDengue is a global public health problem but no antiviral agent exists for dengue. This study explores the antiviral potential of the aqueous extract of Glycyrrhiza glabra (GG) roots on dengue viruses. Virus inhibition in Vero cell lines infected with dengue virus serotypes 1-4 and treated with GG extract was demonstrated. GG extract was 98-100% inhibitory to all four serotypes and had moderate pan-serotype inhibitory activity. It had good potential as an antiviral agent with low cytotoxicity. This is the first report of significant anti-dengue viral activity of GG extract on all four dengue serotypes.