Annual Research & Review in Biology

Aims: The aim of this study was to synthesise 8-bromo-4-(2-(1-phenylethylidene)hydrazinyl)tetrazolo[1,5-a]quinoxaline derivatives and assess their acetylcholinesterase and butyrylcholinesterase inhibitory potential.

Methods: The 8-bromo-4-(2-(1-phenylethylidene) hydrazinyl)tetrazolo[1,5-a]quinoxaline derivatives were synthesised by reacting 8-bromo-4-hydrazinyltetrazolo[1,5-a]quinoxaline 1 with 10 different aromatic ketones. The resulting compounds were characterised using nuclear magnetic resonance (NMR) spectroscopy. Acetylcholinesterase and butyrylcholinesterase inhibitory activities were assessed spectrophotometrically using acetylthiocholine and butyrylcholine chloride as substrates. Molecular docking studies were performed by docking compounds 1(a-h) against the 3D structure of recombinant human acetylcholinesterase.

Results: Compounds 1f (IC₅₀ = 0.14 ± 0.01 µg/mL) and 1c (IC₅₀ = 0.23 ± 0.08 µg/mL) demonstrated the highest inhibitory activity against acetylcholinesterase, while compounds 1f (IC₅₀ = 1.25 ± 0.06 µg/mL), 1h (IC₅₀ = 1.60 ± 0.04 µg/mL), and 1a (IC₅₀ = 2.20 ± 0.21 µg/mL) were the most potent inhibitors of butyrylcholinesterase. Docking studies revealed that compound 1f exhibited the strongest binding affinity among the tested compounds, although it was slightly lower than that of the reference drug, donepezil. Compounds 1d, 1e, and 1c showed binding affinities of -11.4, -11.2, and -11.1, respectively, while compounds 1b and 1h had binding affinities of -10.9.

Conclusion: The significant inhibitory activity of the synthesised compounds against both acetylcholinesterase and butyrylcholinesterase suggests that they are promising candidates for the development of selective inhibitors targeting these enzymes.