Structural studies and antileishmanial activity of 2-acetylpyridine and 2-benzoylpyridine nitro-imidazole-derived hydrazones

Three imidazole hydrazone compounds, namely 2-(4-nitro-1H-imidazol-1-yl)-N'-[1-(pyridin-2-yl)ethylidene]acetohydrazide, C12H12N6O3, (1), 2-(2-nitro-1H-imidazol-1-yl)-N'-[1-(pyridin-2-yl)ethylidene]acetohydrazide, C12H12N6O3, (2), and 2-(2-nitro-1H-imidazol-1-yl)-N'-[(phenyl)(pyridin-2-yl)methylidene]acetohydrazide, C17H14N6O3, (3), were obtained and fully characterized, including their crystal structure determinations. While all the compounds proved not to be cytotoxic to J774.A1 macrophage cells, (1) and (3) exhibited activity against Leishmania chagasi, whereas (2) was revealed to be inactive. Since both (1) and (3) exhibited antileishmanial effects, while (2) was devoid of activity, the presence of the acetyl or benzoyl groups was possibly not a determining factor in the observed antiprotozoal activity. In contrast, since (1) and (3) are 4-nitroimidazole derivatives and (2) is a 2-nitroimidazole-derived compound, the presence of the 4-nitro group probably favours antileishmanial activity over the 2-nitro group. The results suggested that further investigations on compounds (1) and (3) as bioreducible antileishmanial prodrug candidates are called for.