Cyclooctadiene Ru(II) complexes of thiophene-2-carboxaldehyde-derived thiosemicarbazones: synthesis, characterization and antiamoebic activity

Thiosemicarbazones (TSC) 1–10 were synthesized by condensing substituted thiosemicarbazide with thiophene-2-carboxaldehyde. These thiosemicarbazones were further reacted with [Ru(η4 –C8H12)(CH3CN)2Cl2] to form complexes of the type [Ru(η4 –C8H12)(TSC)Cl2] 1a–10a. Thiosemicarbazones exhibited antiamoebic activity in the range IC50 = 1.09–5.42 μM. In vitro assessment of antiamoebic activity indicated that the thiosemicarbazones 3, IC50 = 1.67 μM, 4, IC50 = 1.11 μM and 6, IC50 = 1.09 μM showed substantially less IC50 value than metronidazole (IC50 = 1.87 μM), a commonly used drug against amoebiasis. Cyclooctadiene Ru(II) complexes of thiosemicarbazones showed significant improvement in antiamoebic activity (IC50 = 0.30–1.39 μM). All the complexes possess noteworthy potencies and showed less IC50 values than metronidazole against HK-9 strain of Entamoeba histolytica. Among all the complexes, the most promising antiamoebic activities was shown by the complexes 4a and 6a (IC50 = 0.31 μM of 4a and IC50 = 0.30 μM of 6a versus metronidazole).

Graphical AbstractThiosemicarbazones (TSC) 1–10 and their [Ru(η4 –C8H12)(TSC)Cl2] complexes 1a–10a were synthesized. Thiosemicarbazones exhibited antiamoebic activity in the range IC50 = 1.09–5.42 μM. Cyclooctadiene Ru(II) complexes of thiosemicarbazones showed significant improvement in antiamoebic activity (IC50 = 0.30–1.39 μM). All the complexes possess noteworthy potencies and showed less IC50 values than metronidazole.Figure optionsDownload as PowerPoint slide