Discovery,Structure Modification And Anti-AD Activity Study Of Amide Compounds From Lycium Barbarum L.

Objective: The dried fruit of Lycium barbarum L.is a traditional Chinese medicine(TCM),which has been used to help nourish the liver and kidney,and strengthen eyesight.The current studies showed that wolfberry can effectively prevent Alzheimer's disease,but the structure and mechanism of its active substances are still unclear.Alzheimer Disease(AD)as the main type of dementia had seriously affected people's health and social development.In order to find compounds having anti-AD activity in Lycium barbarum L.,the dried wolfberry was extracted and separated with various methods,and two amide compounds and two dimer amide compounds were separated and identified from its 70% ethanol extract.These amide compounds have the same structural skeleton with gx-50 that is a drug candidate for AD by searching literatures.Therefore,the structure modification,activity evaluation,active mechanism and structure-activity relationship of these compounds were studied in this paper,which provided a scientific basis for anti-AD drug development.Methods: The extracts of dried wolfberry extracted by 70% ethyl alcohol was separated by various separation techniques,chemical structures were determined and confirmed by NMR and MS data analysis as well as literature comparison.Based on the isolated monomer amide compounds,a series of structure analogues 1-20 were designed and synthesized,and the anti-AD activity of these compounds was evaluated with gx-50 as a control.The DPPH assay and thioflavin T(ThT)assay were employed to evaluate their anti-oxidative activity and their inhibition and disaggregation on A? aggregation.Finally,Pavlov?s olfactory memory test was used to evaluate rescue effects on memory loss for the behavior of AD model flies.Results: Two monomer amide compounds and two dimer amide compounds,as well as a coumarin and a flavonoid,were obtained from wolfberry.The anti-AD activitys of the monomeric amide compound 1-20 were studied.DPPH results shown the compounds concentration and their anti-oxidative activity exhibited a favorable concentration-dependent relationship.Compounds 9–16 exhibited comparable DPPH scavenging activity compared to the positive control while the DPPH scavenging capability of compound 3(gx-50)was weak.ThT result shown compounds 3 has less inhibitory and disaggregate potency.Compounds 13–16 exhibited equal or better inhibitory and disaggregate potency than curcumin and resveratrol.The most active compound was compound 15 which sample solution was imaged with transmission electron microscope,and the results were in agreement with the the ThT test.Compounds 3 and 13–16 were selected to explore whether they could rescue the memory loss of the Drosophila AD model.The result showed that the rescue effect on memory loss of compound 13 was comparable to that of the positive control drug memantine at the same concentration.Moreover,compound 13 was also far more effective than gx-50(compound 3).Conclution: Compound 13 should be a promising lead compound for the treatment of AD by comprehensively considering the anti-AD activity of compounds 1-20.In addition,the absolute configuration of the dimer amide compounds in wolfberry,as well as its anti-AD activity and structure-activity relationship study need the further study.