Forty-eight hour treatment with compounds 5b, 5d, and 5e (80 μmol/L) failed to increase ROS (A), reduce the level of MMP (B), or induce senescence (C) in the presence of NAC (10 mmol/L). Microscopic photographs (×400) were taken with a phase contrast microscope (Nikon). (D) There was no difference in the relative quantity of ROS, MMP and SA-β-Gal positive cells in the treated group compared to the control group (P>0.05 vs control group; n=3).