Synthesis, dyeing performance and evaluation of the antimicrobial and antioxidant activities of azo dye derivatives incorporated with 1,3,4-thiadiazole combined with in silico computational studies

Abstract

The incorporation of heterocyclic moieties into azo dye derivatives influences the bioactive properties of synthesized derivatives. Herein, six azo dye derivatives incorporated with 1,3,4-thiadiazole, a five membered heterocyclic scaffold, were prepared from 4-dimethylaminobezaldehyde/4-aminobenzoic acid, thiosemicarbazide and coupling agents (phenol, 1-naphthol, and 2-naphthol) through a diazotization-coupling reaction with good yields. The structures of the synthesized compounds were characterized using UV-visible; FTIR; and ¹H, ¹³C and DEPT-135 NMR techniques. The fastness properties of compounds 12 and 13 were tested, and they were found to display excellent fastness to washing and rubbing. The compounds were also evaluated for their antimicrobial activities against six bacterial and three fungal strains using the broth dilution method. Among the tested derivatives, compound 13 showed good antimicrobial activity (MIC = 0.5 mg mL⁻¹) against both bacterial and fungal species compared to ciprofloxacin (0.0125 mg mL⁻¹) and ketoconazole (0.05 mg mL⁻¹). The antioxidant activities of the compounds were evaluated through DPPH assay, and compound 13 displayed radical scavenging activity with an IC₅₀ value of 8.4 μg mL⁻¹, which was relative to that of ascorbic acid (IC₅₀ = 9.6 μg mL⁻¹). In silico molecular interaction studies showed that compound 12 exhibited higher binding affinity (−8.0 kcal mol⁻¹) toward E. coli DNA gyrase B than ciprofloxacin (−7.3 kcal mol⁻¹). Similarly, compounds 10 and 13 displayed the highest binding affinity (−6.1 kcal mol⁻¹) toward S. aureus PK compared to ciprofloxacin (−4.9 kcal mol⁻¹). Compound 13 displayed the highest binding affinity (−10.6 kcal mol⁻¹) toward C. albican CYP51 compared to KC (−10.2 kcal mol⁻¹). Further, compound 13 showed the highest binding affinity (−5.8 kcal mol⁻¹) toward human peroxiredoxin 5 compared to ascorbic acid (−4.2 kcal mol⁻¹). Compound 10 revealed the lowest chemical hardness (0.0453 eV) and the highest softness (22.0751 eV) due to the lowest energy gap, which inferred the highest reactivity of the compound.