Cell viability was determined using neutral red assay[19], with slightly modified. The cells were seeded in 96-well plates at a density of 1×105 cells/mL and incubated for 24 h. After removal of medium, the cells were treated with 100 µL of TSCE at concentrations ranging from 0.05 to 1 mg/mL for 24 h. The TSCE was removed and then washed twice with 100 µL of phosphate buffer solution (PBS) (pH 7.4) and then H2O2 was added to induce the cell damage. About 100 µL of 40 µg/mL neutral red medium was added and incubated for 3 h. After incubated the neutral red medium was removed and rapidly washed and fixed with 100 µL of fixing solution. The dye was extracted by adding 100 µL of extraction solution, incubated for 20 min, and then agitated on a rocking platform for 5 min. An absorbance was measured at 570 nm using micropalte reader (Wallac 1420, Perkin Elmer, USA). The cell viability was calculated compare with vehicle control (0.25% DMSO in medium).