Cell viability assay

The cell viability was determined by 3-[4, 5-dimethylthiazol-2-yl]-2, 5 diphenyl tetrazolium bromide (MTT) cell viability assay. Briefly, a total of 5×10³ cells were planted in a 96-well plate and then incubated with different concentrations of BJ for times as indicated. Solution containing MTT (0.5 mg/mL; Sigma-Aldrich Co.) was added and incubated for 3 hours. Dimethyl sulfoxide was added to dissolve the crystals. The absorption at 570 nm with 630 nm as the reference wavelength was measured by a Microplate ELISA Reader. Relative cell viability was calculated as the percentage of the control. All cell viability assays were performed in triplicate and repeated in three independent experiments.