It is well-known that an increase of intracellular ROS can lead to
apoptosis. On the other hand, a decrease of ROS can also ruin the
stability of mitochondria, which is followed by a loss of mitochondrial
membrane potential, release of cytochrome c into cytosol, and
cascade activation of caspases.27,28,30,32 The occurrence of the
apoptotic process should be confirmed by the presence of caspase-
3 and -9 (which played a crucial role and was a key element
in the execution phase of apoptosis). The enzyme activities of caspase-
3 and -9 were determined by spectrophotometry (Fig. 9).
After incubation with compound 7b for 24 h, the activities of caspase-
3 and -9 increased compared with the control. As shown in
Figure 9, the results clearly showed that an induction of cell apoptosis
took place when the cells were treated with compound 7b,
and the stimulation of caspase-3 and -9 activities both increased
in a time dependent manner from 3 to 24 h.