Enzymatic synthesis of new aromatic esters of phloridzin

Lipase B from Candida antarctica immobilized on a macroporous acrylic resin (Novozym 435(R)) 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 80degreesC. 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 80h. 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. (C) 2003 Elsevier B.V. All rights reserved.