3.2. Cell Viability Assay

RAW264.7 cells were plated at 5 × 10³/well and cultured in complete RPMI-1640 medium containing 5% heat inactivated serum, 100 U/mL penicillin and 100 mg/mL streptomycin, in incubator under 5% CO₂ at 37 °C for 24 h. Compounds were dissolved in DMSO and diluted with 1640 medium to the desired concentrations. Cells and compound solutions were incubated for 72 h together, then 5 mg/mL fresh MTT solution was added to every hole and the cells were cultured for another 3 h in the CO₂ incubator. One hundred milliliters of DMSO was used as blank control, and the optical density was recorded at 590 nm. Cell viability is usually expressed as the ratio of absorbance.