Synthesis and Urease Inhibitory Properties of Some New N4-Substituted 5-Nitroisatin-3-thiosemicarbazones

A series of seventeen N4-substituted 5-nitroisatin-3-thiosemicarbazones 2a-2q has been synthesized and screened for in vitro urease inhibitory activities. Compounds 2a-2d, 2g, 2i, 2j and 2q were found to be potent inhibitors of the enzyme. Of these, 2c exhibited a potent inhibitory activity with IC50 value 16.4 μM and may act as a lead molecule for further studies. Structure-activity relationship studies revealed that electronic effects of the substituents play an important role in the urease inhibitory potential of the synthetic compounds.