Synthesis, characterization and in silico study of (E)-4-bromo-2-(1-(2-phenylhydrazineylidene)ethyl)phenol for antioxidant activity and for the inhibition of enzymes

A new hydrazone–Schiff base was synthesised through the reaction of phenylhydrazine with an acetophenone derivative in a methanolic medium. The target compound was successfully obtained as brown crystals in a high yield. Its structure was thoroughly characterised using various spectroscopic techniques, including FTIR, UV–Vis, LC–MS, 1 H NMR, 13 C NMR, and DEPT-135. Furthermore, the structure of ( E )-4-bromo-2-(1-(2-phenylhydrazinylidene)ethyl)phenol (HSBr) was confirmed by two-dimensional (2D) NMR (HSQC and HMBC), which showed the correlation between the carbon and hydrogen atoms within the molecule. The antioxidant activities of HSBr were evaluated in vitro using ABTS •+ scavenging, FRAP, and phenanthroline assay. The results demonstrated that HSBr exhibited notable antioxidant activity, with an IC 50 value of 11.69 ± 0.01 μM, A 0.5 = 20.87 ± 0.03 μM, and A 0.5 = 6.35 ± 0.02 μM in the ABTS, FRAP, and phenanthroline assay respectively. Additionally, the compound showed promising enzyme inhibitory activity against acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and urease, with IC₅₀ values of 41.04 ± 0.09 μM, 117.93 ± 0.14 μM, and 56.16 ± 0.28 μM, respectively. Moreover, in silico molecular docking simulations were conducted to examine the antioxidant potential, the anticholinesterase and urease inhibitory activity of HSBr with the proteins 2E1Q, 2CDU, 1OG5, 2×08, 3MNG 4EY7, 4BDS, and 3LA4. Molecular properties of HSBr were investigated using density functional theory (DFT) at the B3LYP/6-311+G(d,p) level. The electronic properties, molecular electrostatic potential (MESP), Mulliken atomic charges, and chemical reactivity and stability were calculated to determine potential regions for electrophilic and nucleophilic attack in the molecule. In summary, the computational results were in good agreement with the experimental findings, thereby confirming the proposed molecular structure and properties.