After 24 h preincubation at 37 °C in a humidified atmosphere of 5% CO2/95% air to allow cellular attachment, various concentrations of test solution (10 μL/well) were added and these were then
incubated for 48 h under the above conditions. At the end of the incubation, 10 μL of tetrazolium reagent was added into each well followed by further incubation at 37 °C for 4 h.