Discovery of Schiff bases as potent antibacterial and antifungal agents†

In recent years, compounds from the Schiff base group have been intensively studied for their biological activities. Accordingly, a series of Schiff bases were synthesized from substituted aromatic aldehydes (5-chlorosalicylaldehyde) and differently substituted aromatic amines and their antimicrobial activities were evaluated. The molecular identity of compounds was confirmed using various spectroscopic techniques, such as IR and NMR spectroscopy and elemental analysis, and the molecular structure of compound 3k was determined by single-crystal X-ray analysis. The antimicrobial activity of 3a–3k compounds was examined in sixteen microorganisms (five species of bacteria and eleven species of fungi) using the microdilution method. Regarding antibacterial activity, a remarkable MIC value (0.0098 mg mL⁻¹) and, therefore, the best activity was displayed against Proteus mirabilis for 3e, which is even stronger than the most frequently used antibiotic medications. 3f showed the best antifungal activity against Microsporum gypseum, which is stronger than standard antimycotic fluconazole, and is also an important result considering that Microsporum gypseum can cause dermatophytosis in both humans and animals.