After 24 hours of incubation, a volume of 200 µL of the indicated concentration of the respective compounds was added into the appropriate triplicate wells with the final concentrations of: 0.625, 1.25, 2.5, 5, 10, 20 µM. CT26 cells were incubated with the compounds for 24 h, followed by cell washing with medium. To assess cell viability, resazurin blue (Sigma, diluted in PBS, phosphate buffer solution) was used (150 µL in each well, 0.1 mg mL -1 ). After ca. 1.5 h, the fluorescence of resorufin, the metabolic product that results from resazurin reduction, was recorded with a microplate reader (Biotek Synergy HT) using 528/20 nm excitation and 590/35 nm emission filters. The experiment was repeated three times, and the final cell viability was accessed after merging the mean values of all the independent experiments. The statistical significance analysis was applied by using Graphpad software.