Bioactivity of pyridine-2-thiolato-1-oxide metal complexes: Bi(III), Fe(III) and Ga(III) complexes as potent anti-Mycobacterium tuberculosis prospective agents

In the search for new therapeutic tools against tuberculosis and to further address the therapeutic potential of pyridine-2-thiol 1-oxide (Hmpo) metal complexes, two new octahedral [MIII(mpo)<inf>3</inf>] complexes, withM Combining double low line Ga or Bi, were synthesized and characterized in the solid state and in solution. Attempts to crystallize [GaIII(mpo)<inf>3</inf>] in CH<inf>2</inf>Cl<inf>2</inf>led to single crystals of the reaction product [GaCl(mpo)<inf>2</inf>], where the gallium(III) ion is in a square basis pyramidal environment, trans-coordinated at the basis to two pyridine-2-thiolato 1-oxide anions acting as bidentate ligands through their oxygen and sulfur atoms.The biological activity of the new [MIII(mpo)<inf>3</inf>] complexes together with that of the previously reported Fe(III) analogous compound and the pyridine-2-thiol 1-oxide sodium salt (Na mpo) was evaluated on Mycobacterium tuberculosis. The compounds showed excellent activity, both in the standard strain H<inf>37</inf>Rv ATCC27294 (pan-susceptible) and in five clinical isolates that are resistant to the standard first-line anti-tuberculosis drugs isoniazid and rifampicin. These pyridine-2-thiol 1-oxide derivatives are promising compounds for the treatment of resistant tuberculosis.