Microwave-assisted synthesis and butyrylcholinesterase inhibitory activity of new azobenzene derivatives

Cholinesterase inhibitors (ChEis) play an important role enhancing cholinergic synaptic activity and, consequently, have therapeutic applications in the treatment of neurodegenerative diseases like Alzheimer's disease (AD). The inhibition of the enzymes acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) avoids the degradation of the neurotransmitter acetylcholine and constitutes a pharmacotherapeutic strategy that has shown important efficacy reducing AD symptoms.

Based on previous results obtained by our group and with the purpose of obtaining diverse and more effective compounds, a series of new azobenzene derivatives were designed and synthesized. Additionally, considering the powerful AChE inhibition displayed by this type of compounds, in this work, it was decided to expand the research by testing BChE inhibitory activity. Nine azobenzene derivatives, with different spacer lengths (4-8 carbons) and terminal tertiary amines, were synthesized by microwave-assisted synthesis and tested for biological activity in vitro. The synthesis was carried out using a microwave oven (in two steps) with a reaction time of around 20 min and moderate to good yields. Also cytotoxic properties of the compounds in SH-SY5Y human neuroblastoma cells will be tested.

The inhibitory activity of BChE was determined using Ellman's method. All the compounds synthesized were active against BChE, being the most effective the one with a six carbon atom spacer and ethylbenzylamine moiety (IC₅₀: 6.621 µM ± 0.001). From these results we could establish that the optimum length for the spacer was six carbons and that diamines were less active than monoamines.