5‐Arylidene‐2,4‐thiazolidinediones as Cysteine Protease Inhibitors against Leishmania Donovani

Abstract

AbstractA series of 5‐arylidene‐2,4‐thiazolidinediones were synthesized using Knoevenagel condensation and evaluated for their anti‐leishmanial activity against L. donovani promastigotes and axenic amastigotes. Among the compounds tested, three were the most active, with IC50 values of 0.82–1.42 μM against L. donovani promastigotes and 0.69–1.19 μM against L. donovani amastigote. (Z)‐5‐(4‐(trifluoromethyl)benzylidene)thiazolidine‐2,4‐dione was the most prominent among all the tested compounds and demonstrated better anti‐leishmanial properties when compared to the standard drug miltefosine (1.26 μM against L. donovani promastigotes and 1.17 μM against L. donovani amastigotes). It was insignificantly toxic compared to the standard miltefosine in THP‐1 human monocytic cells. It was further evaluated for its in vitro cysteine protease (papain) inhibitory activity using Z‐RR‐AMC fluorogenic peptide substrate. It demonstrated promising inhibitory activity with the IC50 value of 3.42 μM. In silico docking studies also supported that the (Z)‐5‐(4‐(trifluoromethyl)benzylidene)thiazolidine‐2,4‐dione is bound to cysteine protease proteins′ catalytic active binding site. Anti‐leishmanial properties of this class of compounds have been evaluated for the first time, and (Z)‐5‐(4‐(trifluoromethyl)benzylidene)thiazolidine‐2,4‐dione emerged as a lead molecule from the library of compounds tested. This may serve as a template for further drug discovery in Leishmania.