2.4. Cell Viability Assay

Cell viability was measured by MTT assay. MCF-7 cells were seeded at a density of 5 × 10³ cells per well in 96-well plates and treated with various concentrations of Rb1, R-Rg3, S-Rg3, and Rg5. At the indicated time, MTT was added to the wells followed by incubation for 4 h. Afterwards, dimethyl sulfoxide was added to dissolve the formazan crystals. The optical density of the solution at 490 nm was measured using a microplate reader (Biotek, Burlington, VT, USA). The probit model was used to compute IC50 values.