Synthesis, Cytotoxic, Antibacterial and Free Radical Scavenging Activities of Schiff Bases Derived from 1,2,4-Triazole

A series of new 1,2,4-triazole Schiff bases incorporating a chlorinated indole moiety were prepared from the condensation reaction of 4-amino-5-mercapto-3-[(5-chloro-2-methyl-1H-indol-3- yl)methyl]1,2,4-triazole with substituted benzaldehydes in the presence of (+)-tartaric acid as an acidic catalyst. The structures of Schiff bases were elucidated by FTIR, NMR and mass spectral data. The cytotoxic, antibacterial and free radical scavenging activities of Schiff bases were performed using MTT, 96-well microbroth dilution and DPPH assays, respectively. Schiff bases 3k and 3l with both electron donating groups at meta and para positions of the phenyl ring demonstrated higher cytotoxic activity against COLO-205 and A549 cell lines. On the other hand, Schiff base 3f comprising p-chlorophenyl substituent exhibited significant inhibition against Bacillus cereus and Staphylococcus aureus at MIC 3.91 μg/ml and 15.63 μg/ml, respectively. The results of the free radical scavenging activity revealed that Schiff bases with the presence of a Cl or OCH3 group in the para position of the phenyl ring act as a better antioxidant than BHT.