Serial dilutions
of extract, fractions, or compounds, as well as the reference compound
chloroquine, were prepared in assay medium [MEM Rega3 (cat. no.
19993013; Invitrogen), 2% FCS (Integro), 5 mL of 200 mM Lglutamine,
and 5 mL of 7.5% sodium bicarbonate] that was added to
empty wells of a 96-well microtiter plate (Falcon, BD). Subsequently,
50 μL of a 4× virus dilution in assay medium was added, followed by
50 μL of a cell suspension. This suspension, with a cell density of 25
000 cells/50 μL, was prepared from a Vero cell line subcultured in cell
growth medium (MEM Rega3 supplemented with 10% FCS, 5 mL of
L-glutamine, and 5 mL of sodium bicarbonate) at a ratio of 1:4 and
grown for 7 days in 150 cm2 tissue culture flasks (Techno Plastic
Products). The assay plates were returned to the incubator for 6−7
days (37 °C, 5% CO2, 95−99% relative humidity), a time at which
maximal virus-induced cell death or cytopathic effect (CPE) is
observed in untreated, infected controls.