Synthesis And Cholinesterase Activity Evaluation Of Chalcone And Its Cyclization Derivatives

The research and development of acetylcholinesterase inhibitors(AChEI)has been a hot research area of looking for anti-Alzheimer’s disease(AD),clinical research shows AChEI can improve cognition in AD patients without doubt.In recent years,the drugs to combat Alzheimer’s disease ended in failure,which were design based on amyloid-beta,5HTR6 or BACE1.Therefore,the development of novel AChEI remains the main method for the drugs to combat Alzheimer’s disease.In our prophase research,we screened flavokawain B derivatives containing the skeleton of chalcone,most of them have the inhibitory activity of AChE.And then,we synthesized a series of acetylcholinesterase inhibitors,such as tertiaryamines-substituented chalcone derivatives,halogenated chalcone derivatives and chalcone analogues which containing heterocycles,all of them have different degrees of biological activities of inhibiting AChE.The study on structure-activity relationship shows the kinds of aromatic and tertiary amine substituents,carbon chain length can affect the inhibitory activity of the derivatives.But our team didn’t research the influence of the way of cyclization of α,β-unsaturated carbonyl group,the position of tertiary amine substituents.In this paper,we explore the structure-relationship by setting the different nitrogen atom in different position or obtaining five-member or six-member heterocyclic ring through cyclization the α,β-unsaturated carbonyl group,in order to further study the influence of the kind and position of tertiary amine substituents or the importance of the α,β-unsaturated carbonyl group.We explore the structure-activity relationship of the derivates to develop high potent and high selective AChEIs.The main contents were summarized as following:(1)A series of novel chalcone derivatives with five tertiary amine groups in the A-ring were designed and synthesized,the compound exhibited the most potent biological activities of inhibiting AChE were choose to study the relationship of chains and biological activities.In order to explore if the α,β-unsaturated carbonyl group is necessary for the activity,under the action of hydrazine hydrate and hydroxylamine hydrochloride,a series of heterocyclic derivatives were prepared by means of cyclization.The study on structure-activity relationship shows tertiary amine groups is necessary for the activity,but the α,β-unsaturated carbonyl group is not.Their inhibitory activity increased with donor ability of the tertiary amine groups and heterocyclic.For most of compounds,the inhibitory potency of chalcone derivatives against AChE followed the order:pyrrolidine>piperidine>dimethylamine>diethylamine>morpholine.Chalcone derivate B4e(IC50=1.64±0.01 μmol/L,selective:3.02)showed the most potent inhibitory activity and higher selectivity against AChE,and then heterocyclic derivate B12e(IC50-1.64±0.01 μmol/L,selective:3.02)showed the most potent inhibitory activity and higher selectivity against AChE.When side chain,for example formoxyl and acetyl,were introduced into pyrazolylheterocycle,the inhibitory activity will reduce 13.8-fold and 10.6-fold,respectively.(2)A series of novel hydroxychalcone derivatives with tertiary amine groups in the A-ring were designed and synthesized,in order to explore the optimum configuration of them,a series of flavonoid derivatives,dihydroflavone derivatives and flavan-4-ol derivatives were prepared by cyclization and reduction.The study on structure-activity relationship shows the way of cyclization of α,β-unsaturated carbonyl group greatly influenced the inhibitory activity and selectivity against AChE and BuChE.The inhibitory potency of Flavonoids derivatives against AChE followed the order:Flavan-4-oI<Dihydroflavones<Chalcones<Flavonoids,when tertiary amine groups were introduced into 3’ of Flavonoids,the inhibitory potency of Flavonoids derivatives against BuChE followed the order:Flavan-4-ol<Chalcones<Dihydroflavones<Flavonoids,when tertiary amine groups were introduced into 4’ of Flavonoids,the inhibitory potency of Flavonoids derivatives against BuChE followed the order:Flavan-4-ol<Dihydroflavones<Chalcones<Flavonoids.The replacement position of tertiary amine groups also greatly influenced the inhibitory activity and selectivity against AChE and BuChE,for most of compounds,the inhibitory potency of Flavonoids derivatives against AChE followed the order:para-substituted>meta-substituted>ortho-substituted,however,the inhibitory potency of them against BuChE followed the order:ortho-substituted>meta-substituted>para-substituted.Except for few,the derivates have pyrrolidine-substituent or piperidine-substituent have more potent against AChE than the one with dimethylamine-substituent or diethylamine-substituent.Flavonoids derivates G3e、G3d and G3b have the most potent inhibitory activity and higher selectivity against AChE,the half inhibition concentration of which is 0.43±0.03,0.42±0.04 and 54±0.01 pmol/L.(3)The software of molecular docking is utilized to further study the combination way of target compounds and AChE protein molecules at the molecular level to validates the correctness of the design idea in this paper and interpret the effect of structural differences on biological activity.The study of molecular docking shows the derivates exhibited multiple point binding modes with AChE.The quaternary nitrogen binds to the catalytic active site(CAS)via the π-cation interaction with Trp84,and.the aromatic rings at the top of peripheral anionic site(PAS)interact with the ring of amino acid residues through a π-π stacking.After cyclization theα,β-unsaturated carbonyl group,the five-or six-membered heterocycle also can interact with AChE through a π-π stacking or hydrogen bond,which explained that α,β-unsaturated carbonyl group is not necessary for the activity on the molecular level.Enzyme kinetics experiments showed the derivates presented a mixed-type inhibition,which is in accordance with molecular docking.