New Pd(II) complexes of the synthesized 1-N-substituted thiosemicarbazones of 3-indole carboxaldehyde: Characterization and antiamoebic assessment against E. histolytica

Reaction of 3-indole carboxaldehyde with aminothiocarbonyl hydrazines resulted in the formation of 3-indole carboxaldehyde thiosemicarbazones (TSCs) 1-13. The synthesized thiosemicarbazones were used as ligands in the formation of [Pd(TSC)Cl₂] complexes with palladium(II) metal ion precursor, [Pd(DMSO)₂Cl₂]. The chemical structures of all the compounds were established by electronic, IR, ¹H NMR and ¹³C NMR spectral data. The structure of the complexes was further established by FABMS and DTA. It is concluded that the thione sulphur and the azomethine nitrogen atom of the ligands are bonded to the metal ion. The testing of the antiamoebic activity of these compounds against the protozoan parasite Entamoeba histolytica suggests that compounds 5, 3a, 5a and 8a-13a might be endowed with important antiamoebic properties since they showed less IC₅₀ values than metronidazole. Moreover, compound 12a displays remarkable antiamoebic activity than metronidazole (IC₅₀ values of 0.29 vs 1.81 μM, respectively). MTT assay showed that the compounds are non-toxic to human kidney epithelial cell line.