Lipase-Catalyzed Synthesis Of Oleyl Ferulate

Oleyl ferulate (OF) is a compound of oleyl alcohol (OA) and ferulic acid (FA) connected by an ester bond and can be used as a natural antioxidant in both lipid containing food and cosmetic. We describe for the first time the lipase-catalyzed synthesis of the OF by transesterification between OA and ethyl ferulate (EF) in organic solvents and solvent-free medium. The ability of lipases to catalyze the transesterification between OA and EF were investigated respectively by TLC and HPLC.Using Novozym435as catalyst, transesterification of ethyl ferulate (EF) with four different fatty alcohols were carried in organic solvents to form fatty ferulate. In order to investigate the most suitable medium for the transesterification, tertiary butanol, toluene, hexane, isooctane were tested for lipase-catalyzed transesterification of ethyl ferulate with oleyl alcohol. Hexane has been found to be the optimal organic solvent. But the results showed that the yield of OF in solvent-free system was higher than that in hexane, so the solvent-free system is more desirable.The influences of water activity (aw), the reaction temperature, the ratio of enzyme to substrate, the molar ratio of substrates, stirring rate and the reaction time on the yield of OF were studied in detail in order to obtain the optimum conditions for OF synthesis. When the molar ratio of oleyl alcohol (OA) to ethyl ferulate (EF) was5:1,water activity was<0.01.the ratio of enzyme to substrate was5%(W/W).the temperature and stirring rate were60℃and200r/min respectively, the maximum conversion of53.2%was reached after96h in solvent-free medium.Using Novozym435as catalyst, transesterification of ethyl ferulate with oleyl alcohol to form OF in solvent-free medium was investigated. It has been observed that water activity (aw) had obvious influence on transesterification efficacy. The yield of OF increased with increasing aw from<0.01to0.05. In order to enhance the yield of OF and decrease the hydrolysis of substrate, adding silica gel to system has been used instead of increasing aw. The maximal yield of OF57.6%was, obtained using5%silica gel/substrate (W/W)in solvent-free medium. The yield of OF was further enhanced by applying vacuum-rotary evaporation procedure to remove the co-product ethanol. The elimination of ethanol co-product under reduced pressure resulted in the shift of the reaction equilibrium position in favor of synthesis.65%of OF was synthesized within96h. The enzyme can be reused for9runs, and the yield of OF was still maintained62%.