Design, synthesis and antitubercular potency of 4-hydroxyquinolin-2(1H)-ones

In this study, a 50-membered library of substituted 4-hydroxyquinolin-2(1H)-ones and two closely related analogues was designed, scored in-silico for drug likeness and subsequently synthesized. Thirteen derivatives, all sharing a common 3-phenyl substituent showed minimal inhibitory concentrations against Mycobacterium tuberculosis H37Ra below 10 μM and against Mycobacterium bovis AN5A below 15 μM but were inactive against faster growing mycobacterial species. None of these selected derivatives showed significant acute toxicity against MRC-5 cells or early signs of genotoxicity in the Vitotox™ assay at the active concentration range. The structure activity study relation provided some insight in the further favourable substitution pattern at the 4-hydroxyquinolin-2(1H)-one scaffold and finally 6-fluoro-4-hydroxy-3-phenylquinolin-2(1H)-one (38) was selected as the most promising member of the library with a MIC of 3.2 μM and a CC₅₀ against MRC-5 of 67.4 μM.