(A) Changes in membrane potential (red/green fluorescent ratio of DiOC2) of M. bovis BCG cultures treated with test compound 11d (12 μM), 12a (24 μM), 14 (24 μM), 16 (24 μM), rifampicin (RIF, 0.08 μM), and CCCP (100 μM). 11d and 12a were tested at 4× MIC90. MIC90 was redetermined for this experiment and were 3 μM (11d) and 6 μM (12a). Mean and SD of three biological replicates. Means were significantly different from drug-free (DF) controls at time zero (without CCCP) with p <0.05 (*), <0.01 (**), and <0.001 (***), Student’s t test, Graph-Pad Prism, Ver 5.0. (B) Corresponding changes in viability of treated cultures (CFU/mL) under similar conditions described in (A).