Determination on the involvement of ROS in the cytotoxicity of DCM-DS in MCF-7 cells. (A) Measurement of intracellular ROS in DCM-DS-treated MCF-7 cells by using DCFH-DA (Sigma-Aldrich). (B) Cell viability of MCF-7 cells co-treated with α-tocopherol or ascorbic acid for 24 and 48 hours. Each data point represents the mean of three independent experiments ± SD. a and b were significantly different among the concentration at the same time point (p < 0.05).