Substituted Phenylthiazole Derivatives: Synthesis, Spectral and Biological Investigation

The present study aimed to synthesize and characterize a group of novel phenylthiazoles and, finally, discovered their antioxidant and antimicrobial efficacy in reducing infectious diseases. The agar disk diffusion method evaluated their antimicrobial efficacies against fungal strains (Aspergillus niger, Trichoderma harzianum), gram-positive (Staphylococcus aureus, Bacillus megaterium), and gram-negative (Salmonella typhi, Escherichia coli) bacterial strains. 2,2-Diphenyl-1-picrylhydrazyl (DPPH) and total antioxidant capacity (TAC) methods were used to measure their antioxidant efficacies. Among the tested analogs, we detected the maximum antifungal efficacy for 4-{[2-(4-phenylthiazol-2-yl)hydrazineylidene]methyl}phenol, followed by 2-[2-(4-chlorobenzylidene)hydrazineyl]-4-phenylthiazole. Nevertheless, 5-bromo-2-{[2-(4-phenylthiazol-2-yl)hydrazineylidene]methyl}phenol produced the lowest inhibition zone against T. harzianum. However, the antifungal efficacies for the synthesized compounds were significantly higher than the standard amphotericin B. In contrast, the highest efficacy of the compound 4-{[2-(4-phenylthiazol-2-yl)hydrazineylidene]methyl}phenol is 1.3 times greater than Amphotericin B. Besides, the highest antibacterial efficacy was detected for 4-{[2-(4-phenylthiazol-2-yl)hydrazineylidene]methyl}phenol, followed by 2-[2-(4-chlorobenzylidene)hydrazineyl]-4-phenylthiazole, which was 0.4 times lower than standard ceftriaxone. Moreover, the lowest inhibition zones were achieved for 5-(diethylamino)-2-{[2-(4-phenylthiazol-2-yl)hydrazineylidene]methyl}phenol. The antioxidant screening was done using DPPH free radical inhibition capability and TAC methods. However, both methods ensured that 5-(diethylamino)-2-{[2-(4-phenylthiazol-2-yl)hydrazineylidene]methyl}phenol is a highly potent antioxidant.