*3.3. Sulforhodamine B Assay*

HCT116 cells (2 × 104 cells/mL) were seeded in 96-well plates with various concentrations of SA and incubated at 37 ◦C in a humidified atmosphere with 5% CO2. After incubation, the cells were fixed with a 50% trichloroacetic acid (TCA) solution for 1 h, and cellular proteins were stained with 0.4% sulforhodamine B (SRB) in 1% acetic acid. The stained cells were dissolved in 10 mM Tris buffer (pH 10.0). The effect of SA on cell proliferation was calculated as a percentage relative to a solvent-treated control, and the IC50 values were evaluated using nonlinear regression analysis (percent survival *versus* concentration).
