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Etude de la voie de biosynthèse de la galanthamine chez Leucojum aestivum L. : criblage phytochimique de quelques amaryllidaceae

Abstract : Galanthamine is an Amaryllidaceae alkaloid used worldwide for the symptomatic treatment of Alzheimer's disease because of his capacity to inhibit the acetylcholinesterase enzyme. There are two galanthamine sources for medical applications. One is the total synthesis, a complicated process because galanthamine has three asymmetric carbons, requiring stereochemically controlled synthesis. Galanthamine is also extracted from bulbs of some Amaryllidaceae such as Leucojum aestivum, Galanthus nivalis, and Narcissus sp.. The first aim of this work is to improve the accumulation of this alkaloid using biotechnologies. The second aim consists on the phytochemical screening (HPLC, LCMS, GCMS, et HPTLCMS) of in vivo and in vitro Amaryllidaceae bulbs, in order to identify new alkaloids with important pharmacological activities. Finally, the third aim concerns the study of the biosynthesis pathway in order to establish a biomimetic synthesis of galanthamine. Therefore, we established in vitro cultures of three Amaryllidaceae species. The variation of exogenousparameters led to the obtainment of high galanthamine accumulation (0.02 to 0.2 % DW). The phytochemical screening showed new alkaloids in extracts of in vitro cultures, which did not exist in in vivo extracts, and possessing high acetylcholinesterase activity (40 to 80 % Inh). The 4'-O-methyl-d3-norbelladine is incorporated into three different groups of Amaryllidaceae alkaloids. The addition of the labelled precursor to shoot cultures stimulated the synthesis of native galanthamine (0.15 % DW and 0.16 % Culture medium).
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Anna El Tahchy. Etude de la voie de biosynthèse de la galanthamine chez Leucojum aestivum L. : criblage phytochimique de quelques amaryllidaceae. Autre. Université Henri Poincaré - Nancy 1, 2010. Français. ⟨NNT : 2010NAN10072⟩. ⟨tel-01748647⟩



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