Viability of cells was calorimetrically analyzed by using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT). To find out the cytotoxic effect of Celastrol and rotenone, briefly, SH-SY5Y cells were cultured in serum-free media for 24 hours with or without Celastrol (20 to 200 µM) and rotenone (10 to 80 µM) f. After the incubation period, MTT was added (5 mg/ml) and incubated for 3-4 hrs. After incubation, the blue formazan which was formed during this process was dissolved in DMSO and measured Spectrophotometrically at 550 nm. Vehicle controls were exposed to 0.05 % (v/v) DMSO (dimethyl sulphoxide) in the culture medium are maintained as blanks.