Germacrone-induced apoptosis in MDA-MB-231 cells was determined by a TUNEL assay. As expected, germacrone increased the TUNELpositive cell population of MDA-MB-231 cells undergoing apoptosis
(Fig. 4). The percentage of TUNEL-positive cells in the positive control
group was 51.40% (Fig. 4A). Compared with negative control (0.77%)
(Fig. 4B), a low concentration of germacrone (50 μM) showed no
significant effect on apoptosis (0.23%) ( Fig. 4C), while 100 μM
germacrone induced a low but statistically significant increase in
apoptotic rate (2.10%) (Fig. 4D and F). However, the percentage of
TUNEL-positive cells was significantly increased by 200 μM germacrone
treatment (45.13%) for 24 h (Fig. 4E and F)