ROS generation was assessed using a ROS-sensitive fluorescence indicator
DCFH-DA (Lebel and Bondy, 1990). To determine intracellular ROS scavenging activity, RAW 264.7 cells (2.0 104 cells/well) were seeded in black 96-well plates. After 24 h, the cells were treated with samples and t-BHP (200 lM) for 2 h to induce ROS generation. After the cells were incubated with DCFH-DA (20 lM) for 30 min, and the fluorescence intensity was measured at an excitation wavelength of 485 nm
and an emission wavelength of 530 nm using a fluorescence microplate reader
(Bio-Tek Instruments Inc., FLx 800, Winooski, UT, USA).