Novel Tryptanthrin Derivatives:A Multi-target Ligand For The Treatment Of Alzheimer’s Disease

Alzheimer’s disease（AD）is a common dementia disease characterized by progressive and irreversible loss of memory and cognitive functions due mainly to neuronal dysfunction,especially within the cholinergic system of the brain.The pathogenesis of AD is still unclear,but several well-known hypotheses have been proposed,such as the cholinergic hypothesis,the oxidative stress hypothesis,the neuroinflammatory hypothesis,the aggregation of neurotoxic amyloidβ（Aβ）,and metal ion chelation.Among them,the cholinergic hypothesis is by far the most prominent of the AD hypotheses.The hypothesis proposes that degeneration of cholinergic neurons and depletion of cholinergic neurotransmitters in the cerebral cortex are the main causes of the deterioration of cognitive function observed in the brains of AD patients.Acetylcholinesterase（ACh E）and butyrylcholinesterase（Bu Ch E）,two cholinesterases（Ch Es）used for acetylcholine hydrolysis in the brain,are a major neurotransmitter that plays a key role in learning and memory.Studies have shown that low levels of acetylcholine（ACh）are strongly associated with symptomatic cognitive impairment in patients with AD.Therefore,increasing acetylcholine levels by inhibiting cholinesterase is an effective strategy to improve cognitive function.Furthermore,due to the complex pathogenesis of AD,it is difficult to reduce to a single therapeutic factor involving multiple related etiologic targets that will affect a wide range of pathologies and symptoms.The"single-molecule,single-target"treatment model cannot achieve good therapeutic results.Instead,"multi-targeted ligands"（MTDLs）are a powerful and effective strategy,as they can play an important role in the effective treatment of multifactorial disease progression such as AD.Moreover,MTDLs obtained according to this approach can modulate multiple biological targets simultaneously,offering higher efficacy,better safety and simpler drug delivery.In this study,we synthesized two series of tryptamine derivatives with benzenesulfonamide substituents and evaluated their activity as multifunctional ligands for the treatment of AD based on a multi-target directed ligand（MTDLs）approach.In vitro biological experiments showed that most of the derivatives possess good cholinesterase inhibitory activity and neuroprotective properties.Among them,the target compound 4h was considered as a mixed reversible dual inhibitor of acetylcholinesterase(ACh E,IC₅₀=0.13±0.04μM)and butyrylcholinesterase(Bu Ch E,IC₅₀=6.11±0.15μM)（dissociation constants Ki of 0.0831μM and 5.3268μM）.And we found by thioflavin T（Th T）fluorescence analysis that compound 4h could also potentially prevent amyloid plaque generation by inhibiting Aβaggregation（63.16±2.33%）.Transmission electron microscopy（TEM）was used to further analyze the inhibitory activity of the compound on Aβaggregation.Next,molecular docking studies were used to explore the interaction of 4h on ACh E,Bu Ch E and Aβ.In addition,significant anti-neuroinflammatory potency(NO,IL-1β,TNF-α;IC₅₀=0.62±0.07μM,1.78±0.21μM,1.31±0.28μM)and a dose-dependent reduction in the expression of the inflammatory factor COX-2 with i NOS in LPS-induced BV2 cells were found in compound 4h.Also,4h effectively reduced the production of ROS in LPS-induced BV2 cells and showed the same inhibitory effect on H₂O₂-induced reactive oxygen species（ROS）in SY5Y and PC12 cells.In addition,4h also exhibited 1,1-diphenyl-2-picrylhydrazyl（DPPH）radical scavenging and metal ion chelation,and the maximum absorption intensity at 261 nm was reduced after the addition of Cu Cl₂ solution to the 4h solution.Further studies showed that 4h has proper blood-brain barrier（BBB）permeability in bidirectional transport assays.In vivo studies,4h was effective in improving learning and memory deficits in a scopolamine-induced AD mouse model.These findings suggest that 4h may be a promising compound for further development of multifunctional agents for the treatment of AD.