Novel Pd(II) complexes of 1-N-substituted 3-phenyl-2-pyrazoline derivatives and evaluation of antiamoebic activity

Cyclization of Mannich base with N⁴-substituted thiosemicarbazides by different aliphatic, aromatic and cyclic amines afforded a series of new 1-N-substituted cyclised pyrazoline analogues of thiosemicarbazones (PYZ-TSC) 1-10. Reaction of [Pd(DMSO)₂Cl₂] with pyrazoline derivatives led to new palladium(II) complexes [Pd(PYZ-TSC)Cl₂] 1a-10a. The structures of all the compounds were characterized by spectroscopic methods. It was concluded that the pyrazoline thiosemicarbazone derivatives have two chelating arms, one attached at the 2-position of the pyrazole ring (that is, N donor) and other (S donor) linked to the thiosemicarbazone branch. The determination of antiamoebic activity of all the compounds was done using HM1:IMSS strain of Entamoeba histolytica, among all the complexes, 8a showed the most promising IC₅₀ = 0.37 μM vs. IC₅₀ = 1.81 μM of metronidazole, the reference drug. MTT assay showed that the compounds are non-toxic to human kidney epithelial cell line.