After 24 hours of incubation, a volume of 200 µL of the indicated concentration of the compounds (from 0.625 to 20 µM) was added into the appropriate triplicate wells. The cells were then incubated with the compounds for an additional period of 24 h, In case of compound 17, which exhibited dark toxicity at 20 µM, the final tested concentrations were adjusted from 0.31 to 10 µM while compound 13h included concentrations from 0.04 to 5 µM or 0.08 to 10 µM.