The dried and powdered plant material (each 10 g) was extracted successively with n-hexane, dichloromethane and methanol in a soxhlet extractor for each 8 h. Evaporation of the solvent followed by drying in vacuum gave the respective crude dry extract. Only methanol extract was used for the antiviral assay, n-hexane and dichloromethane extracts were not included because of their insolubility in medium and high toxicity to the cells. Each 2 mg of the extract was dissolved in 10 ml dimethylsulfoxide (DMSO) before adding tissue culture medium supplemented with 2% fetal calf serum (FCS, GIBCO Life science technologies, Paisley, UK) and stocked at a concentration of 2 mg ml À1 .