Effects of compounds 5b, 5d, and 5e on the cell cycle distribution of A549 cells. Cells were exposed to compounds 5b, 5d, and 5e (80 μmol/L) for 48 h. The values are expressed as the percentage of the cell population in the G1-, S-, and G2-phases of the cell cycle. A, Control; B, 5b; C, 5d; D, 5e.