Synthesis and characterization of indole-3-butyric acid-based hydrazones: from multifunctional enzyme inhibition to therapeutic potential for drug development

Abstract

The present study explores the synthesis, spectroscopic characterization, and biological profiling of indole-3-butyric acid-derived hydrazones, notably 1-(4-amino-3,5dichlorophenyl) ethylidene-4-indol-3-butanehydrazide hydrazone and 4-indole-3-butane-(thiophen-2-ylmethylene) hydrazide hydrazone. The structural integrity of the synthesized compounds was confirmed by UV-Vis spectroscopy, FTIR, EI-MS, and ¹H and ¹³C NMR, while thermal analyses (DSC and TGA) provided insights into their thermal stability. Molecular docking and molecular dynamics simulations were employed to assess binding affinity, conformational stability, and thermodynamic parameters. Biological investigations included enzyme inhibition, antioxidant, anticancer, and antibacterial evaluations. The thiophene-based compound exhibited potent acetylcholinesterase inhibition (IC₅₀ 1.95 ± 10.79 μM), surpassing the standard donepezil (IC₅₀ 4.53 ± 0.13 μM), and demonstrated effective α-amylase inhibition (IC₅₀ 0.99 ± 2.6 μM), comparable to acarbose (IC₅₀ 4.21 ± 0.27 μM). This compound also showed pronounced cytotoxicity against HeLa (96.31%, IC₅₀ 49.2 ± 0.02 μM) and PC-3 (97.42%, IC₅₀ 41.1 ± 0.11 μM) cell lines in comparison with standard doxorubicin (HeLa 98.7%, IC₅₀ 1.13 ± 0.18 μM and PC-3 80.8%, IC₅₀ 1.18 ± 0.21 μM). The aminodichlorophenyl derivative demonstrated superior inhibition of tyrosinase (IC₅₀ 0.96 ± 1.005 μM), compared to kojic acid (IC₅₀ 1.0 ± 0.3 µM), along with higher antioxidant activity (IC₅₀ 5.95 ± 1.16 μM) relative to ascorbic acid (IC₅₀ 7.3 ± 1.4 μM). Antibacterial assays revealed enhanced activity against Gram-positive (51.3 ± 3.5 mm) compared to cefixime (27 ± 0.31 mm) by aminodichlorophenyl derivative and Gram-negative (15.0 ± 0.12 mm) bacterial strains compared to cefixime (29 ± 0.17 mm) by thiophene-based compounds. The in silico results aligned closely with experimental findings, validating computational predictions. The incorporation of sulfur and halogen along with amino moieties was found to enhance biological efficacy, highlighting their relevance in future drug design. These findings suggest the therapeutic potential of indole-based hydrazones as multifunctional pharmacological agents.

Keywords: ADMET; Anticancer; Bioactivity; Enzyme inhibition; Hydrazones; Indole-3-butyric acid; Molecular dynamics.