Although caffeic acid phenethyl ester (CAPE), an active flavonoid, plays an important role in the antioxidant
activity of honeybee propolis, the isolation of CAPE from honeybee propolis is time-consuming due to wide
variety of impurities present. Therefore, biochemical method to synthesize CAPE was investigated in this study.
Since ionic liquids (ILs) possess some unique characteristics as appreciated alternatives to conventional solvents for
certain biotransformation, the effect of ILs as reaction media for enzymatic synthesis of CAPE was assessed.
Several factors including substrate molar ratio, and reaction temperature affecting the conversion yield of lipase-catalyzed
CAPE synthesis were also investigated. Reaction yields were significantly higher in hydrophobic ILs than in
hydrophilic ILs (almost zero). Among nine hydrophobic ILs tested, the highest conversion of synthetic reaction was
obtained in 1-ethyl-3-methylimidazolium bis[(trifluoromethyl) sulfonyl]imide ([Emim][Tf2N]). A reaction temperature
of 70 C was found to give high conversion. In addition, optimal substrate molar ratio between phenethyl
alcohol and caffeic acid (CA) was decreased significantly from 92:1 to 30:1 when ILs were used instead of isooctane.