Synthesis And Acetylcholinesterase Inhibition Activity Evaluation Of Chalcone Derivatives

Alzheimer’s disease, senile dementia, is a common neurodegenerative disease.The main symptom of AD is cognitive function, visuospatial function and memoryfunction declining，which make personal life ability, social life ability and emotionalpersonality decrease significantly. So far, the “the cholinergic deficiency hypothesis”is still said to be the world’s most widely accepted pathology. This theory believes thatthe lack of acetylcholine in the brains of patients resulting in nerve excitabilityunnormal delivering is the key reason of causing AD. The cholinomimetic developedbased on “the cholinergic deficiency hypothesis” remain the main drugs of the clinicaltreatment on Alzheimer disease.Chalcone, a natural product, exhibit diverse biological activities and may bindeffectively to enzyme or receptor because of the flexible structure. Combining withthe“the cholinergic deficiency hypothesis”、 the structure of acetylcholine and thedesign principle of cholinomimetic drugs, firstly, the activities of eight flavokawain Bderivatives on acetylcholinesterase(AChE) were researched preliminarily in vitro;secondly, according to the result of the activies study, we designed and synthesized anew series of chalcone derivatives with differenr chains to explore further thestructure-function relationship by the method of simplify the structure; lastly, theactivities of the chalcone derivatives were study in vitro to select the compound withhigh inhibition against AChE.The main contents were sunmmarized as following:(1) The hydroxylamine-chloride ferric method and the Ellman method wereoptimized and comparison, and the result showed that the Ellman method had theadvantages including high sensitivity, the AChE consume decreasing, and thecoloration of direct effect on the product.(2) flavokawain B derivatives were evaluated for the inhibition activity againstAChE by the Ellman method. Biological results revealed that five compoundsdisplayed high activities against AChE with IC50values below20μM. Moreover, themost promising compound A6was2-fold more active than Rivastigmine, a well-knownAChE inhibitor and others IC50were18.8、15.1、16.1and12.4μM respectively. Thenthe compounds with high activities against AChE were made enzyme kinetic study,which suggested that the inhibition mechanism of compounds A2, A3, A5, A8weremixed-type inhibition. Meanwhile, to study the ligand combining with AChE in molecule level, all compounds made the molecular docking, and the result showed thatcompound A2, A3, A5, A6and A8can both bind with the catalytic site and the peripheryof AChE.(3) The log P values were measured to research the ability through blood-brainbarrier by combining the shake-flask and HPLC mehod. The values were around2.0which indicated that they were sufficiently lipophilic to pass blood brain barriers invivo.(4) A new series of chalcone derivatives with differenr chains were designed andsynthesized to explore further the structure-function relationship by the method ofsimplify the structure, and the structures were characterized by1H NMR and IR.(5) The chalcone derivatives were measured for the inhibition activity againstAChE by the Ellman method. The result showed that the compound with chain length4had the highest activity, meanwhile pyridine and pyrrole ring substituent was higherthan dimethylamino and diethylamino substituent, and the IC50of B5creached0.85μM,secondly compound B5dwas1.42μM. Then the compounds B5cwas made enzymekinetic study, which suggested that the inhibition mechanism was mixed-typeinhibition. And the molecular docking showed that this compound can both bind withthe catalytic site and the periphery of AChE.