Purification And Alky-modification Of Galanthamine And The Structure-activity Relationship On Inhibiting AChE Activity

Alzheimer's disease (AD), a progressive degenerative disease of the nervous system, is one of the most common causes of mental deterioration to old people. Every year, the cost for the AD patient's medication and care is the third after the most costly diseases caner and heart disease in US. Currently, the most mature and successful treatment of the AD is treated with acetylcholinesterase inhibitors (AChEIs), which is so far the only type of drug for the treatment of AD approved by the FDA in the United States..Galanthamine is an alkaloid that is obtained from the bulbs and flowers of the Caucasian snowdrop (Voronov's snowdrop), Galanthus woronowii (Amaryllidaceae) and related genera like Narcissus (daffodil), Leucojum (snowflake) and Lycoris including Lycoris radiata (Red Spider Lily). It is a long acting, selective, reversible and competitive acetylcholinesterase (AChE) inhibitor. But the lower yield and higher cost curbed the application of galanthamine in clinic. In this study, the extract technology, the alkylated modification and the structure-activity on inhibiting AChE of galanthamine were investigated.1. Galanthamine extractionThrough the process of ethanol extraction and separation of single-factor test, the concentration of ethanol, solid-liquid ratio, extraction temperature and time as the level of each factor orthogonal experiment were determined. By the orthogonal test, the optimum condition was as follows:the ratio of material to liquid was 1:10, the concention of ethanol 95%, extracting temperature 85℃under reflux extraction two times, each time 2h. The extraction rate was up to 81.2%.2. Purification of galanthamineGalanthamine is separated and purified by two methods:one is the method with ethyl acetate at pH8.5, by which the yield of galanthamine was about 77%, and the purity of galanthamine was 22.77%. Another method is HPLC preparation, by which the yield of galanthamine was 50.8%, and its purity was 92.52%.3. N-Alkylated modification of galanthamineThe effects of reaction time and reactant ratio on N-alkylated modification of galanthamine were investigated. The results showed that galanthamine derivatives with a high yield would be obtained when the ratio of galanthamine to alkyl bromides was 1:5 after reacting 36h. The structure of galanthamine derivatives were confirmed by the analysis of UV, IR, TLC, 1HNMR and 13CNMR.4. Galanthamine and itsderivatives on the AChE inhibitionAccording to the enzyme and molecular-docking results, alkylated modification at N.atom of galanthamine could enstrengthen the inhibition to AChE activity, with the alphatic chain elongating. Among the synthesized compound, N-dodecyl-galathamine (C12-GAL)showed the best improved effects on inhibiting AChE activity.