Synthesis and Evaluation of Thiadiazole-based Antileishmanial Agents

The 1, 3, 4-thiadiazole scaffold is one of the principal structural components, in a variety of drug categories such as antimicrobial, anti-inflammatory, antineoplastic, and antileishmanial agents. Considering the reported antileishmanial effects of thiadiazole derivatives and the importance of this disease, some of the thiadiazole derivatives with modifications at sulfur atom or amine group attached to the 2-position were synthesized and evaluated for antileishmanial activity.

Derivatives of 1,3,4-thiadiazole including 2-substituted-thio-1,3,4-thiadiazoles bearing (5-(4-nitrobenzylideneamino) or 5-amino (II, IV, V) and one derivative of 2-substituted-amino1,3,4-thiadiazole bearing (5- (4-nitrophenyl) (VII) were synthesized and evaluated for their in vitro antileishmanial activity against promastigote and amastigote forms of the Leishmania major.

The most active compound was found to be compound II after 24-h incubation against promastigotes and amastigotes with the half maximal inhibitory concentration (IC50) values of 44.4 µM and 64.7 µM, respectively.

All of the synthesized compounds showed good antileishmanial activity against both forms of L. major after 48 and 72h incubation.