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To evaluate the anti-mycobacterial activity, the redox microplate Alamar BlueVR assay was performed. The assay was performed on 96-well polystyrene flat bottom plates with low evaporation cover lids. First, 200 uL of sterile distilled water was added to the perimetral wells and 100 uL of Middlebrook 7H9 broth supplemented with OADC was added to the remaining wells. The working solutions of compounds (512 lg/mL) were distributed into the first well of each row, from which a 2-fold dilution series was made using the following three wells. The final concentrations in-test ranged from 128 to 16 ug/mL. Then, 100 uL of the Mtb inoculum was added. Rifampin was used (15–9.15*10^-4 ug/mL) as a control. Simultaneously, a 1:100 dilution prepared from the bacterial inoculum (representing the growth of 1% of the bacterial population) and a growth control were included. As negative controls, 200 lL of culture medium alone and 200 lL of the maximum tested concentration of the compounds (without bacteria) were used. The plates were incubated at 37 C. After 5 d of incubation, 50 lL of a fresh Alamar Blue-10% Tween 80 mixture (1:1) was added to each control well. The microplate was sealed with parafilm and reincubated for 24 h at 37 C. If the negative controls remained blue and the positive controls turned pink, the reagent mixture was added to all of the wells in the microplate. The microplates were resealed with parafilm and incubated for an additional 48 h; then, the colors of all wells were recorded. Finally, the visual MICs were defined as the lowest compound or antibiotic concentration at which no color change in the indicator was evident.