We have evaluated the antiproliferative activity of (E)-3-(3,5-difluorophenyl)-1-(2,4,6-trimethoxyphenyl)- prop-2-en-1-one (chalcone 5) against MGC-803 cells. This chalcone analog displayed a potent antiproliferative activity with an IC50 value of 0.23 μM against MGC-803 cells. It could induce apoptosis and regulate the apoptosis-related markers (Bax, Bcl-2, Bcl-xl, and Bid) in a concentration dependent manner. Treatment with NAC almost completely attenuated chalcone-induced cell inhibition and cell apoptosis in MGC-803 cells, indicating that the apoptotic mechanisms were related to ROS generation. Therefore, this chalcone derivative is a new apoptosis inducer for prevention and treatment of gastric cancer. [ABSTRACT FROM AUTHOR]