Design,Synthesis And Evaluation Of 2,3-dihydrobenzo[b][1,4]dioxin Substituated Chalcone Derivatives As Novel Monoamine Oxidase B Inhibitors

Objective:MAO-B can be functioned as a catalyst for oxidative degradation of various monoamines in the human body,such as a neurotransmitter called dopamine.Its increased activity or abnormal expression will reduce the level of neurotransmitter and cause oxidative damages to nerve cells.Clinically,MAO-B was regarded as an important target for the treatment of a variety of neurodegenerative diseases.However,most existing clinical drugs that target MAO-B have disadvantages such as high toxicity and poor selectivity.Therefore,research and development of new MAO-B inhibitors with high efficiency,good selectivity,and low toxicity and side effects have become hot topics.Natural chalcone isoliquiritigenin,as one of the active ingredients in traditional Chinese medicine licorice,has been shown to have a certain inhibitory effect on MAO-B,but the structure-activity relationship was not clear.It was expected to improve its inhibitory activity and selectivity through structural optimization.Based on this,a series of chalcone derivatives were synthesized from the parent structure of isoliquiritigenin through structural modification in order to explore its structure-activity relationship.Under the guidance of the obtained structure-activity relationship,a newly discovered active molecular skeleton was designed and synthesized,a chalcone compound library was established,and the activity screening was performed to find a highly selective MAO-B inhibitor with good inhibitory activity,and good drug labeling properties.Methods:The parent structure of chalcone?1,3-diphenyl-2-propenone?was used as the basic skeleton.A series of derivatives,including isoliquiritigenin and2,3-dihydrobenzo[b][1,4]dioxin-substituted chalcone derivatives were synthesized via Alkali-catalyzed Claisen-Schmidt condensation reaction method by applying computer-aided design.Further,the in vitro inhibitory activity,inhibition type,and enzyme inhibition of the compounds were analyzed reversibly using fluorescence detection.Physicochemical parameters of the active substance were calculated using drug design software,and its effect on the inhibition of neuronal cell proliferation was evaluated using the MTT method,and its medicinal properties were initially discussed.Results:?1?A total of 52 compounds were synthesized in this paper,of which 49 have not been reported to have inhibitory effects on MAO-B.The purity and structure of the compounds have been verified by UPLC,¹H-NMR,¹³C-NMR,and HRMS.?2?The test results of the enzyme inhibitory activity showed that the inhibitory activity of25 compounds on MAO-B was more than 70%at a concentration of 1?M,among which C24,C25,C30,C45,and C50 represented better inhibitory ability with the IC₅₀ of 0.057?M,0.055?M,0.026?M,0.021?M and 0.042?M respectively,close to or better than existing clinical drugs safinamide and rasagiline.The enzyme kinetics and reversibility experiment revealed that the above-mentioned compounds are competitive reversible inhibitors.Besides,the inhibitory activity of these compounds on MAO-A was less than50%at the concentration of 40?M,which implied a good inhibitory specificity on MAO-B.The MTT results further indicated that the representative compounds C24,C25,C30,and C45 had a lower level of neurotoxicity on mice BV2 microglial cell.?3?The calculation results of drug-like related physicochemical parameters showed that the active compounds conform to the Lipinski's rule and have a great potential to penetrate the blood-brain barrier.Conclusion:?1?52 compounds were successfully synthesized in this thesis,of which 49 compounds with inhibitory effects on MAO-B were reported for the first time;?2?25 compounds showed good inhibitory effects on MAO-B,with IC₅₀ less than 0.34?M,relatively high selectivity,and selectivity index greater than 119.The inhibitory effects of its representative compounds are also named as competitive inhibitors C24,C25,C30,C45,and C50 on MAO-B are nearly equivalent to the clinical drug safinamide.More importantly,these compounds are superior to clinical drugs selegiline and rasagiline as reversible inhibitors.C24,C25,C30 and C45 have low levels of cytotoxicity to BV2 cells.?3?The active compounds and central nervous system-related drugs share certain physical and chemical properties,and have great potential to develop into lead compounds.