Enzymatic synthesis of new aromatic esters of phloridzin

Lipase B from Candida antarctica immobilized on a macroporous acrylic resin (Novozym 435®) was used to catalyze the enzymatic synthesis of acylated derivatives of phloridzin a flavonoid from the dihydrochalcone family. Reactions were achieved under reduced pressure, in the presence of a large excess of acyl donor which also acted as a solvent for the acyl acceptor, phloridzin. The acylation of phloridzin by ethyl cinnamate was shown to be total and perfectly regioselective in favor of phloridzin-6″-O-cinnamate. The kinetic of the reaction was significantly improved by the temperature of the reaction medium best results being obtained at 80 °C. An amount of immobilized enzyme of 20 g l−1 corresponding to 1.2 g l−1 of proteins was chosen in order to obtain the total conversion of phloridzin after only few hours. Increasing phloridzin concentration allowed a maximal production of 119 g l−1 phloridzin cinnamate after 80 h. Other esters like phloridzin-6″-O-benzoate and phloridzin-6″-O-salicylate were also prepared in similar conditions. However, only traces of ester were obtained when phenolic acyl donors like methyl p-hydroxyphenylacetate and methyl p-hydroxyphenylpropionate were used. All esters were purified and characterized.