Intracellular ROS production was estimated by using the method which was described by with slight modifications. Briefly, following 24 h exposure to the test compounds, 20 μL of 2', 7'-dichlorodihydrofluorescein diacetate (H2DCF-DA; 20 μM) in PBS solution was added to the relevant wells and the plates were incubated for 90 min at 37ºC. To remove excess H2DCF-DA solution, the plates were then washed with 100 μL An additional 100 μL of PBS was added to each well and the fluorescence intensity was measured using a BMG Fluostar Optima fluorescent plate reader and read with excitation and emission wavelengths at 492 nm and 525 nm.