Chemical structure of violacein and cytotoxicity in leukemic cell lines and normal human peripheral blood cells. Chemical structure of violacein (A). The cells were treated with different concentrations of violacein for 24 hours (B). In the absence of compounds, the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide) reduction was considered as 100%. The experiment was performed in a 24-well plate. Results represent the means ± standard error of 3 experiments run in triplicate (P < .05).