Synthesis and antimicrobial evaluation of novel 1,2,4-triazole derivatives

Derivatives of 1,2,4-triazole are widely recognized as promising scaffolds for the development of biologically a c tive compounds, particularly those exhibiting antimicrobial properties. In the present study, the antimicrobial potential of a series of newly synthesized 1,2,4-triazole-based heterocyclic compounds was investigated using the in vitro disk diffusion method against 15 clinically significant bacterial strains, including both Gram-positive and Gram-negative species. The compounds were dissolved in 70% ethanol and tested at different concentrations to assess their spectrum and degree of antibacterial activity. One compound, ethyl 2-((3-mercapto-9-methylpyrazolo[1,5-d][1,2,4]triazolo[3,4-f][1,2,4]triazin-6-yl)thio)acetate, exhibited the most pronounced inhibitory effect, producing zones of bacterial growth inhibition exceeding 8 mm in diameter in 14 out of the 15 tested bacterial strains. Several other derivatives, particula r ly those bearing N-ethyl or N-phenyl substitutions within triazolothiadiazole frameworks, as well as dichlorophenyl-substituted triazolothiadiazines, exhibited moderate antibacterial activity, inhibiting the growth of five to seven ba c terial strains depending on their structural features. The structure – activity relationship analysis suggests that the pre s ence of electron-withdrawing groups, fused heterocyclic systems and s ulfur-containing linkages may contribute to enhanced biological activity. Overall, the results underscore the importance of the 1,2,4-triazole core in the design of novel antimicrobial agents and provide a solid foundation for further structural optimization and pharmaceutical d e velopment of these compounds.