Synthesis and Anti‐Amoebic Activity of Gold(I), Ruthenium(II), and Copper(II) Complexes of Metronidazole

A series of Au, Ru, and Cu complexes of metronidazole (=[1‐(2‐hydroxyethyl)‐2‐methyl‐5‐nitro‐1 H ‐imidazole; 1 ) were prepared as highly potent anti‐amoebic drugs. The complexes [Au(PPh 3 )( 1 )]PF 6 ( 2 ), [Ru( 1 ) 2 (Cl) 2 (H 2 O) 2 ] ( 3 ), and [Cu( 1 ) 2 (μ‐Cl)(H 2 O)] 2 Cl 2 ( 4 ) were readily synthesized from [Au(PPh 3 )Cl], RuCl 3 ⋅3 H 2 O, and CuCl 2 ⋅2 H 2 O, respectively. All complexes were thoroughly characterized by IR, UV/VIS, 1 H‐NMR, FAB‐MS, elemental and thermogravimetric analyses, and, in the case of 4 , also by X‐ray crystallography ( Fig. 1 ). All complexes were evaluated in vitro as growth inhibitors of Entamoeba histolytica (HM1 : IMSS strain). Their IC 50 values were in the range of 0.10–0.51 μ M ( Table 2 ), which makes these drugs, especially the Cu II complex 4 , considerably more potent than uncomplexed metronidazole ( 1 ; IC 50 =1.81 μ M ), the current standard drug for the worldwide treatment of amoebiasis.