Fig. 5 Reactive oxygen species (ROS) determination in KB cells treated with compound 3. ROS determination was performed by using a fluorescent probe 2’,7’-dichlorofluorescein diacetate (DCFH-DA), in KB cells untreated and treated with compound 3 at different concentrations for 72 hrs. Stock solution of the compound was prepared in DMSO and the final concentration of this solvent was kept constant at 0.25%. Control cultures received DMSO alone. Each value represents the mean ± SD of three experiments, performed in quadruplicate. *Significant vs. control untreated cells (p < 0.001).