Design, Synthesis, and Evaluation of Novel Ferulic Acid Derivatives as Multi-Target-Directed Ligands for the Treatment of Alzheimer's Disease

Tacrine-Hydrogen Sulfide Donor Hybrid Ameliorates Cognitive Impairment in the Aluminum Chloride Mouse Model of Alzheimer's Disease

Alzheimer's disease (AD) is a neurodegenerative disorder, characterized by progressive loss of memory and cognitive function, and is associated with the deficiency of synaptic acetylcholine, as well as chronic neuroinflmmation. Tacrine, a potent acetylcholinesterase (AChE) inhibitor, was previously a prescribed clinical therapeutic agent for AD, but it was recently withdrawn because it caused widespread hepatotoxicity. Hydrogen sulfide (H₂S) has neuroprotective, hepatoprotective, and anti-inflammatory effects. In this study, we synthesized a new compound, a tacrine-H₂S donor hybrid (THS) by introducing H₂S-releasing moieties (ACS81) to tacrine. Subsequently, pharmacological and biological evaluations of THS were conducted in the aluminum trichloride (AlCl₃)-induced AD mice model. We found that THS (15 mmol/kg) improved cognitive and locomotor activity in AD mice in the step-through test and open field test, respectively. THS showed strong AChE inhibitory activity in the serum and hippocampus of AD mice and induced increased hippocampal H₂S levels. Furthermore, THS reduced mRNA expression of the proinflammatory cytokines, TNF-α, IL-6, and IL-1β and increased synapse-associated proteins (synaptophysin and postsynaptic density protein 95) in the hippocampus of AD mice. Importantly, THS, unlike tacrine, did not increase liver transaminases (alanine transaminase and aspartate transaminase) or proinflammatory cytokines, indicating THS is much safer than tacrine. Therefore, the multifunctional effects of this new hybrid compound of tacrine and H₂S indicate it is a promising compound for further research into the treatment of AD.

The development of 2-acetylphenol-donepezil hybrids as multifunctional agents for the treatment of Alzheimer's disease

A series of 2-acetylphenol-donepezil hybrids was designed and synthesized based on multi-target-directed ligands strategy. The biological activities were evaluated by AChE/BChE inhibition and MAO-A/MAO-B inhibition. The results revealed that the tertiary amines and methylene chain length significantly affected the eeAChE inhibitory potency, in particular, compound TM-14 showed the best eeAChE inhibitory activity with IC₅₀ value of 2.9 μM, in addition, both kinetic analysis of AChE inhibition and docking study displayed that TM-14 could simultaneously bind to the catalytic active site and peripheral anionic site of AChE. Moreover, compound TM-14 was a selective metal chelator and could form 1:1 TM-14-Cu²⁺ complex. The structure-active-relationship also indicated that the O-alkylamine fragment remarkably decreased hMAO-B inhibitory activity, compound TM-2 exhibited potent hMAO-B inhibitory activity (IC₅₀ = 6.8 μM), which was supported by the molecular docking study. More interestingly, compounds TM-14 and TM-2 could cross the blood-brain barrier in vitro. Therefore, the structure-active-relationship of 2-acetylphenol-donepezil hybrids could encourage the development of multifunction agents with selective AChE inhibition or selective MAO-B inhibition for the treatment of Alzheimer's disease.