Analysis of anti-rotavirus activity of extract from Stevia rebaudiana

Anti-human rotavirus (HRV) activity of hot water extracts from Stevia rebau diana (SE) was examined. SE inhibited the replication of all four serotypes of HRV in vitro. This inhibitory effect of SE was not reduced on the prior exposure of SE to HCl for 30 min at pH 2. Binding assay with radiolabeled purified viruses indicated that the inhibitory mechanism of SE is the block ade of virus binding. The SE inhibited the binding of anti-VP7 monoclonal a ntibody to HRV-infected MA104 cells. The inhibitory components of SE were f ound to be heterogeneous anionic polysaccharides with different ion charges . The component analyses suggested that the purified Fraction named as Stev ian with the highest inhibitory activity consists of the anionic polysaccha ride with molecular weight of 9800, and contains Ser and Ala as amino acids . Analyses of sugar residues suggest uronic acid(s) as sugar components. it did not contain amino and neutral sugars and sulfate residues. These findi ngs suggest that SE may bind to 37 kD VP7 and interfere with the binding of VP7 to the cellular receptors by steric: hindrance, which results in the b lockade of the virus attachment to cells. (C) 2001 Elsevier Science B.V. Al l rights reserved.