Synthesis and Biological Evaluation of 2-thiazolylimino-5-arylidene-4- thiazolidinone Derivatives as Potent Antimycobacterial Agents

Background: The recent emergence of multi-drug resistant (MDR) and extensively drugresistant (XDR) cases of tuberculosis has lead to the search for new structural classes of anti-TB drugs that can be effective against these strains of Mycobacterium tuberculosis. In the present study a series of 2-thiazolylimino-5-arylidene-4-thiazolidinone derivatives, unsubstituted and mono-substituted with hydroxy, methoxy, fluoro, chloro and nitro groups on the aryl ring were synthesized and assayed for their in vitro antimycobacterial activity against drug-sensitive M. tb H37Rv strain. Methods: In vitro antimycobacterial activity against drug-sensitive M. tb H37Rv strain (susceptible both to rifampicin and isoniazid) was performed and expressed as % inhibition at minimum inhibitory concentration (MIC) values. Compounds were initially tested for IC99 at a concentration of 6.25 μg/ml in BACTEC-460 TB radiometric system, and Isoniazid (0.1 μg/ml) and rifampicin (2.0 μg/ml) were taken as reference standards. Results: We report the synthesis and antimycobacterial activities of 2- thiazolylimino-5-arylidene-4-thiazolidinone derivatives, expressed as % inhibitions, and their MIC values. All of the above synthesized compounds showed substantial antimycobacterial activity in the preliminary screening, and some of the compounds, 8-14, exhibited excellent antimycobacterial activities (86-98 % inhibition) at 6.25–12.5 μg/ml against drugsensitive M. tb H37Rv strain. Conclusion: The 2-thiazolylimino-5-arylidene-4-thiazolidinone derivatives were identified as a new antitubercular chemical entity in this study. Two of the active compounds, 9 and 14 and their derivatives have been identified as potential lead molecules for further drug development. It was observed that the hydroxyl and bulky alkoxy groups enhance antimycobacterial activity, while a halogen substituent decreases the activity. Further structural optimization and identification of molecules are underway in our laboratory..