Donepezil‐indolyl hybrids as multipotent cholinesterase/monoamine oxidase inhibitors for the potential treatment of Alzheimer’s disease

Abstract Background Numerous laboratory and clinical studies have evidenced that MAO‐B inhibitors are a potential therapeutic approach for the treatment of AD. Thus, drugs used to inhibit activated MAO, including rasagiline, ladostigil and selegiline, may provide neuroprotection against AD by improving cognitive impairment, modulating the proteolytic cleavage of APP and decreasing levels of Aβ protein fragments that accumulate in the brain. Future clinical studies on MAO inhibitors for the treatment of AD may provide further insights into the mechanism of action of antioxidants as therapeutic agents for AD. Method Series of donepezil‐indolyl hybrids were prepared and characterized via highresolution mass spectrometry, 1 H nuclear magnetic resonance and 13 C nuclear magnetic resonance techniques. In vitro fluorometric assay (by Amplex® UltraRed reagent to detect hydrogen peroxide or peroxidase activity in biological samples or enzymes.) was used to investigate the activity of the synthesized compounds on both MAO‐A and MAO‐B isozymes as well as acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) by Ellman method with modifications. Result The biological evaluation of molecules 1‐30 showed that most of these compounds are potent, in the nanomolar range, and selective AChEI, with moderate and equipotent selectivity for MAO‐A and MAO‐B inhibition. In overall, compound 11, as a potent and selective dual AChEI, showing a moderate MAO inhibitory profile, can be considered as an attractive multipotent drug for further development on two key pharmacological targets playing key roles in the therapy of Alzheimer’s disease. Conclusion The pharmacological profile of compound 11, as well as the fact that it is a readily available compound in a short synthetic sequence, in good chemical yields, prompts us to select it as a lead‐compound for further optimization in our current research programme targeted to the preparation of new molecules for the potential treatment of AD.