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Influence de la localisation d’antioxydants sur la peroxydation des lipides membranaires : étude du mode d’action de dérivés PBN et de composés phénoliques

Abstract : Reactive oxygen species (ROS) are essential in living cells as they intervene in several physiological processes like the immune system and signaling pathways. However, an excess of the production of ROS can alter the equilibrium with antioxidants. This imbalance is called oxidative stress. As oxidative stress has been reported to be implicated in more than 200 diseases, the action of antioxidants to limit the deleterious effects of ROS is crucial. The antioxidants used by the cells can be chemical. Among them, α-phenyl-N-tert-butyl nitrone (PBN) is widely used in biological systems to neutralize ROS. Because this molecule possesses a poor ability to target membranes, our collaborators synthesized amphiphilic nitrones bearing a PBN moiety. The first chapter describes the interactions of cholesterol derived PBN derivatives with the membrane. Results underlined the influence of the polar moiety on the nature of their interactions with membrane lipids. In addition, the evaluation of the antioxidant properties revealed the importance of the membrane localization of the nitrone moiety on the protective activity of the derivatives. The second chapter deals with a second set of amphiphilic nitrones that have the particularity of bearing a perfluorinated chain that constitutes the hydrophobic moiety. We noticed the membrane localization is important for the antioxidant efficiency; however the nature of the antioxidant moiety remains the most important parameter in this case. Finally, the strategy of grafting two different antioxidants on the same carrier seems to be promising to enhance the protective effect and create a synergistic antioxidant effect. However, cells also use natural antioxidants to defend themselves. These antioxidants come from food, especially from vegetables and fruits. Among them, phenolic compounds are known for their beneficial effects on health. Flavonoïds, phenolic acids, stilbenes and lignans constitute the 4 main classes of phenolic compounds. Lignans are particularly present in flaxseed (Linum usitatissimum). Flaxseed is the plant that possesses the highest quantity of secoisolariciresinol diglucoside. In order to understand their mechanisms of action and their interactions with membranes, lignans as well as hydroxycinnamic acids were purified from flaxseed. The third chapter describes the results obtained on model membranes. Generally speaking, both classes of compounds are efficient against lipid oxidation. Studying their interactions with membrane lipids allowed us to show that the mechanism of lignans, that penetrate membranes, is more efficient than the mechanism of hydroxycinnamic acids.
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Larissa Socrier. Influence de la localisation d’antioxydants sur la peroxydation des lipides membranaires : étude du mode d’action de dérivés PBN et de composés phénoliques. Biotechnologie. Université de Technologie de Compiègne, 2017. Français. ⟨NNT : 2017COMP2382⟩. ⟨tel-02060926⟩

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