Synthesis, biological activities and computational studies of bis-Schiff base derivatives of 4-hydroxyacetophenone: insights from an <i>in vitro</i>, molecular docking and dynamics simulation approach

This study is based on the synthesis and acetyl and butyryl cholinesterase inhibitory activities of some bis-Schiff base derivatives of 4-hydroxyacetophenone. All the synthesized products (2a-j) were structurally analysed by means of modern spectroscopic methods, including ¹H- and ¹³C-NMR and EI-MS, and finally tested for their ability to inhibit cholinesterase enzymes. In the series, six compounds-2j (IC₅₀ = 15.86 ± 0.38 and 29.23 ± 0.04 μM), 2b (IC₅₀ = 18.58 ± 0.21 and 35.31 ± 0.01 μM), 2a (IC₅₀ = 44.36 ± 0.33 and 77.93 ± 1.46 μM), 2f (IC₅₀ = 48.37 ± 0.06 and 76.35 ± 1.17 μM), 2g (IC₅₀ = 62.28 ± 0.42 and 98.71 ± 1.18 μM), and 2e (IC₅₀ = 98.21 ± 0.01 and 135.7 ± 2.61 μM)-were found to be the most promising inhibitors of acetyl and butyryl cholinesterase enzymes compared with the standard drug galantamine (IC₅₀ = 104.8 ± 1.83 and 156.8 ± 1.83 μM), while the remaining compounds were found to be good-to-less active. Compound 2j displayed the most significant inhibition against AChE and BuChE among the tested bis-Schiff base derivatives, thus emerging as a superior compound to the standard galantamine. The highest activity of this compound is because of the favourable molecular interactions such as strong electrophilicity, high softness and a small energy gap. Molecular docking indicates that the compound 2j acts as a dual inhibitor owing to the formation of hydrophobic and polar interactions. The key structural features that include bromo benzyl and 2-methoxyphenol groups play a vital role in its efficacy, making it a more powerful inhibitor than the standard galantamine.