Rational Design and Multibiological Profiling of Novel Donepezil–Trolox Hybrids against Alzheimer’s Disease, with Cholinergic, Antioxidant, Neuroprotective, and Cognition Enhancing Properties

A novel series of donepezil-trolox hybrids were designed, synthesized, and evaluated as multifunctional ligands against Alzheimer's disease (AD). Biological assays showed that these derivatives possessed moderate to good inhibitory activities against acetylcholinesterase (AChE) and monoamine oxidase B (MAO-B) as well as remarkable antioxidant effects. The optimal compound 6d exhibited balanced functions with good inhibition against hAChE (IC50 = 0.54 μM) and hMAO-B (IC50 = 4.3 μM), significant antioxidant activity (41.33 μM IC50 by DPPH method, 1.72 and 1.79 trolox equivalent by ABTS and ORAC methods), excellent copper chelation, and Aβ1-42 aggregation inhibition effect. Furthermore, cellular tests indicated that 6d has very low toxicity and is capable of combating oxidative toxin (H2O2, rotenone, and oligomycin-A) induced neurotoxicity. Most importantly, oral administration of 6d demonstrated notable improvements on cognition and spatial memory against scopolamine-induced acute memory deficit as well as d-galactose (d-gal) and AlCl3 induced chronic oxidative stress in a mouse model without acute toxicity and hepatotoxicity. In summary, both in vitro and in vivo results suggested that 6d is a valuable candidate for the development of a safe and effective anti-Alzheimer's drug.