Design,Synthesis And Activity Evaluation Of Multifunctional Anti-AD Agents Based On Multicomponent Reactions

Alzheimer’s disease(AD)is a neurodegenerative disease with complex pathogenesis and multiple factors,which is an urgent global health problem.There are few drugs on the market to treat AD and most of them are single-target drugs,which cannot stop or reverse the disease process.Therefore,the exploration of multi-target drugs may be a potentially effective strategy for AD treatment.Oxidative stress plays an important role in the complex pathological process of AD,which can form a vicious circle with Aβ deposition,hyperphosphorylation of Tau and mitochondrial dysfunction.Therefore,antioxidants developed based on oxidative stress process may play a multitarget role and contribute to the discovery of multifunctional anti-AD agents.Multifunctional small molecular agents can be obtained by connecting two or more active drugs or their pharmacophore fragments interacting with the desired target.Multicomponent Reactions(MCRs)are an effective method to rapidly build complex and diverse compound libraries,which allow more scaffold diversity to better adapt to the structural requirements of various targets and are very suitable for the development of multi-target drugs.Studies have shown that some natural antioxidant fragments usually showed additional potencies,including inhibition of Aβ aggregation,inhibition of neuroinflammation,chelating metal ions and other activities related to AD.Therefore,we chose tetramethylpyrazine aldehyde as one kind of baisc fragment,lipoic acid,ferulic acid,caffeic acid,and gallic acid as the carboxylic acid fragments,the commercial isonitrile fragments and meta-,andpara-aminophenol were used as the amine fragments.Finally,20 α-acetoxy formamide ligustrazine derivatives and 18 bisamide ligustrazine derivatives were obtained by using Passerini-3CR and Ugi-4CR,respectively,and their AD-related activities were tested.The specific contents are as follows:In the second chapter,20 α-acetoxyformamide ligustrazine derivatives were synthesized by Passerini-3CR and their antioxidant activities were evaluated.The results showed that the scavenging activities of A3B3,A4B1,A4B2,A4B3,A4B4 and A4B5 on DPPH·and ABTS+·were equivalent or better than Trolox.Subsequently,the activities of the above compounds in inhibiting Aβ1-42 self-aggregation,promoting Aβ142 deaggregation,chelating metal ions,cytotoxicity and protecting SH-SY5Y cells from H2O2-induced oxidative damage were further tested.The results showed that the above compounds could promote the deaggregation of Aβ1-42(15.06%～26.60%)at 10 μM,and A3B3,A4B3,A4B4 and A4B5 could also significantly inhibit the self-aggregation of Aβ1-42(21.03%～81.05%).Moreover,the inhibition of A3B3,A4B1,A4B3 and A4B5 at 50 μM on hBACE-1 were 1-3 times higher than those of ligustrazine,caffeic acid and gallic acid fragments.Most of the compounds showed chelating ability to Cu2+or Fe2+,while A4B2,A4B3 and A4B4 could chelate Fe2+ and Cu2+at the ratio of 1:1.Cytotoxicity experiments showed that compounds except A3B3 did not show cytotoxicity to SH-SY5Y cells at 80 μM.A3B3,A4B1,A4B3,A4B4 and A4B5 could also protect SH-SY5Y cells from H2O2-induced oxidative damage(44.15%～71.29%)at 20 μM.Among them,A4B5 had the best activity with EC50 of 11.88 μM,slightly better than Resveratrol(EC50=19.43μM).The activity results showed that seeking multifunctional anti-AD agents by MCRs was a feasible and effective approach.In order to improve the antioxidant activity and other AD-related activities of compounds,18 bisamide ligustrazine derivatives were synthesized by using Ugi-4CR which could contain more than one active fragment in Passerini-3CR.The antioxidant activities results showed that the scavenging activities of A3B2C1,A3B3C1,A3B2C2,A3B2C3 and A4B3C1 on DPPH·and ABTS+·were equivalent or better than Trolox.Further results showed that the above compounds promoted the deaggregation of Aβ1-42(12.45%-31.68%)at 10 μM,and A3B2C3,A3B2C1,A3B3C1,A4B3C1 and A3B2C2 showed moderate inhibitory effect on the self-aggregation of Aβ1-42(39.82%～65.57%).In addition to A4B3C1,the inhibition of compounds on hBACE-1 were all greater than 35%at 50 μM.Cytotoxicity test showed that all compounds showed no cytotoxicity to SH-SY5Y cells at 80 μM.Also,the above compounds showed 62.75%～95.41%protective effects on SH-SY5Y cells injured by H2O2 at 20 μM.Among them,A3B3C1 had the best protective activity with EC50 of 5.69 μM,which was much better than Resveratrol(EC50=19.43 μM).Western Blot results showed that A3B3C1 acted on Nrf2/ARE signaling pathway,increased the expression of related antioxidant proteins NQO1 and HO-1 to normal cell level and protect SH-SY5Y cells damaged by H2O2.The human liver microsomal clearance CLint(mic)of A3B3C1 was 34.8 mL/min/kg,and the half-life T1/2 was 39.8 mintes.The results of human plasma stability experiment showed that A3B3C1 was relatively stable in human plasma,and less than 7%of the compounds were metabolized after 2 hours.In summary,this study confirmed that using Passerini-3CR and Ugi-4CR were effective way to find multifunctional anti-AD agents.A4B5 and A3B3C1 deserve further development as multi-functional anti-AD agents.