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Nouvelles méthodologies d'extraction, de fractionnement et d'identification : application aux molécules bioactives de l'argousier (Hippophae rhamnoides)

Abstract : Plant materials constitute an important source of natural bioactive molecules. Characterisation of these molecules requires often multiple, long and expensive development steps. The aim of this PhD thesis consists of innovation and development of new methods of extraction, fractionation and identification of natural metabolites from plants. We used sea buckthorn as plant model (Hippophaë rhamnoides, Elaeagnaceae) an Eurasian thorny shrub known to possess various phytochemical properties and pharmaceutical effects. In the first part of this work a ―green‖ solvent-free microwave assisted extraction, based on the combined use of pressure, temperature and microwave irradiation has been developed. This approach allows fast and efficient extraction of phenolic compounds while maintaining an important antioxidant capacity. In the second part of this work, a new multidimensional approach coupling CPC and HPLC-UV-MS was developed. This technique allows the separation at semi-preparative scale and the online identification of isolated molecules. Using this approach, 3 phenolic acids and 20 flavonols from the solvent free sea buckthorn berries extract were identified by HPLC-MS/MS. Antioxidant activity and cytotoxicity of fractions were studied in vitro and in cellulo. In the last part of this work, the antioxidant and antimicrobial potentials of different sea buckthorn organs, which were correlated to the presence of flavonoids and proanthocyanidins has been demonstrated. The CPC-HPLC-UV-MS technique was also applied to the fractionation and the partial identification of compounds extracted from sea buckthorn root.
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Thomas Michel. Nouvelles méthodologies d'extraction, de fractionnement et d'identification : application aux molécules bioactives de l'argousier (Hippophae rhamnoides). Alimentation et Nutrition. Université d'Orléans, 2011. Français. ⟨NNT : 2011ORLE2032⟩. ⟨tel-00677211⟩

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