Design, Synthesis, Biological Evaluation, And Molecular Modeling Studies Of Chalcone-carbamate Esters As Cholinesterase Inhibitors

Alzheimer’s disease(AD)is a debilitating and fatal progressive neurodegenerative disorder always resulting in death over a course that varies from 3 to 20 years.The etiology of AD is not yet entirely known.According to the cholinergic hypothesis for AD pathogenesis,the cognitive impairments in AD correlated with cholinergic deficits such as reduced choline acetyltransferase(ChAT)activity and synaptic acetylcholine synthesis.These observations were made just as the role of the cholinergic system in memory processing and learning began to be more widely appreciated.At the neuronal level,ACh can be degraded by two types of cholinesterase enzymes:acetylcholinesterase(EC 3.1.1.7;AChE)and butyrylcholinesterase(EC 3.1.1.8;BuChE).AChE’s activity is dominant in the healthy brain,as AD progresses,the ratio of BuChE activity to AChE activity may change from 0.6 to as high as 11.0 as AD progresses.Like AChE,increasing evidences for the involvement of BuChE in AD supports it as a drug target for AD treatment.Rivastigmine,a second-generation inhibitor,has a dual inhibitory action on both AChE and BuChE because of its specific inhibitory mechanism of the carbamate structure makes a slow substrate reacting covalently with the active site of the AChE and BuChE.Chalcones,the biogenetic precursors of flavonoids and isoflavonoids,display a broad spectrum of pharmacological activities,suggesting that chalcone derivatives can be as multifunctional agents for AD treatment.In the present study,combining both a carbamate structure of rivastigmine and chalcones,we designed,synthesised,and evaluated chalcone-carbamate analogues as inhibitors of AChE and BuChE.Their structure activity relationships(SAR)and mechanisms of enzyme-inhibitor interactions were studied through molecular modeling technology.Furthermore,the druggability of chalcone-carbamate analogues were evaluated using in silico ADMET prediction and SH-SY5Y cell line assay.The main works in the thesis are shown as follows:(1)A review on the pathogenesis and the therapeutic targets of AD,and the development of anti-Alzheimer drugs.(2)We review the mechanism of carbamic ester as cholinesterase inhibitors and the development of chalcone derivative.(3)In order to discover new lead compounds as cholinesterase inhibitors,we designed and synthesized a series of chalcone-carbamate esters,got a total of 26 target products.24 of 26 compounds had been not reported.All the compounds’ structure were confirmed by 1H NMR,13C NMR and HR-MS,and their purities were tested by HPLC.In this paper,we evaluated all of the componds’(DDDA-1～24、DDDA-2-17、DDDA-2-18)ability to inhibit hAChE and hBuChE.Biological assays demonstrated that DDDA-3 is a dual hAChE and hBuChE inhibitor with submicromolar IC50 vlaues(0.87 and 0.35μM),which are comparable to or slightly better than that of the commercially available drug,rivastigmine.The SAR studies demonstrated that 3-substituted carbamate in A ring could increase inhibitory activity against hBuChE,while 4-or 5-substituted carbamate will loss or decrease the activity,and the alkyl substituent on the carbamoyl nitrogen strongly affects the affinity profile(dimethyl>bis(ethyl(methyl)>diethyl),the most potent inhibitors resulted in methyl derivatives.The detailed mechanisms of enzyme-DDDA3 interactions at atomic level were investigated using molecular docking,molecular dynamics simulations,and binding free energies analyses.Compared with rivastigmine,cell viability assay on the SH-SY5Y cell line showed DDDA-3 has negligible toxicity.Furthermore,in silico ADMET prediction results suggested that DDDA-3 is in the required druggability ranges.Thus,compound DDDA-3 is worthy of further development.