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

Twelve new 1,2,4-triazole Schiff bases bearing a fluorinated indole ring were successfully synthesized. The 1,2,4-triazole Schiff bases were synthesized from the condensation reaction of 4-amino-5-mercapto-3-[(5-fluoro-2-methyl-1H-indol-3-yl)methyl]-1,2,4-triazole with a series of benzaldehyde derivatives in the presence of (+)-tartaric acid as the catalyst. The structures of Schiff bases were elucidated by FTIR, NMR and mass spectral data. All newly synthesized Schiff bases were screened for their cytotoxic, antibacterial and free radical scavenging activities. Schiff bases 6b, 6c, 6i and 6j with hydroxyl group at ortho or meta position of the phenyl ring demonstrated higher cytotoxic activity against COLO-205 cell lines with IC50 94.0-144.3 μmol/mL. Schiff base bearing 2-OH and 5-Cl groups showed moderate antibacterial activity against Bacillus cereus at MIC 151 μmol/mL. On the other hand, compounds 6b (IC50 150.4 μmol/mL), 6e (IC50 146.4 μmol/mL), 6f (IC50 120.9 μmol/mL) and 6g (IC50 146.2 μmol/mL) displayed a better free radical scavenging activity than the standard BHT.