Fonctionnalisation enzymatique de composés phénoliques :synthèses d'esters aromatiques de flavonoïdes glycosylés catalysées par la lipase B de Candida antarctica

Abstract : Flavonoids are polyphenolic compounds characteristic of higher plants. They are largely present in human diet and their properties are likely to interest food, cosrnetic and pharmaceutical industries. The aim of this work was to synthesize phenolic esters of flavonoids by an enzyrnatic process. This acylation should modify their physicochemical properties and eventually enhance their biological properties. Immobilized Candida antarctica lipase B (Novozym 435®) was used to catalyse acylation of flavonoids with various aromatic non activated acyl donors. Aromatic esters of non-substituted acids (benzoic and cinnamic acids) were synthesized with good yields. Best results were obtained by transesterification under reduced pressure. At best, a 99% conversion yield of flavonoid was obtained in 25 h, in the presence of solvent (2-methylbutan-2-ol) at 80°C, 200 mbar. In media where the acyldonor acts as the solvent, total conversion of flavonoid glucosides and neohesperidosides was reached in less than 12 h, at 80°C, 200 mbar. Principal handicap of these syntheses was the low solubility of flavonoid glycosides in organic solvents. All characterized products (phloridzin cinnamate, benzoate, salicylate, isoquercitrin 4ilinamate, neohesperidine dihydrochalcone cinnamate and salicylate) are monoesters regioselectively acylated on position 6 OH of the glycoside moiety (primary hydroxyl). However, Novozym 435® did not synthesize phenolic esters of flavonoids when acyl donor has a phenolic fonction conjugated with the carboxylic function (caffeic acid). An exception resides in the synthesis of flavonoid salicylates which only occurred in methyl salicylate, liquid in our experimental conditions.
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Estelle Enaud. Fonctionnalisation enzymatique de composés phénoliques :synthèses d'esters aromatiques de flavonoïdes glycosylés catalysées par la lipase B de Candida antarctica. Alimentation et Nutrition. Institut National Polytechnique de Lorraine, 2004. Français. ⟨NNT : 2004INPL020N⟩. ⟨tel-01749748⟩

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