Synthesis, spectral studies and in vitro assessment for antiamoebic activity of new cyclooctadiene ruthenium(II) complexes with 5-nitrothiophene-2-carboxaldehyde thiosemicarbazones.

We report here the synthesis, characterization and in vitro antiamoebic activity of 5-nitrothiophene-2-carboxaldehyde thiosemicarbazones (TSC), 1-5, and their bidentate complexes [Ru(eta(4)-C(8)H(12))(TSC)Cl(2)] 1a-5a. The biological studies of these compounds were investigated against HK-9 strain of Entamoeba histolytica and the concentration causing 50% cell growth inhibition (IC(50)) was calculated in the micromolar range. The ligands exhibited antiamoebic activity in the range (2.05-5.29microM). Screening results indicated that the potencies of the compounds increased by the incorporation of ruthenium(II) in the thiosemicarbazones. The complexes 1a-5a showed antiamoebic activity with an IC(50) of 0.61-1.43microM and were better inhibitors of growth of E. histolytica, based on IC(50) values. The most promising among them is Ru(II) complex 2a having 1,2,3,4-tetrahydroquinoline as N(4) substitution.