Using ionic liquid cosolvents to improve enzymatic synthesis of arylalkyl β-d-glucopyranosides

Enzymatic synthesis of various arylalkyl β-d-glucopyranosides catalyzed by prune (Prunus domestica) seed meal via reverse hydrolysis in the mixture of organic solvent, ionic liquid (IL) and phosphate buffer was described. Among four hydrophilic organic solvents tested, ethylene glycol diacetate (EGDA) was found to be the most suitable for enzymatic synthesis of salidroside, a bioactive compound of commercial interest, from d-glucose and tyrosol. The effects of the nature of ionic liquids and their contents on the enzymatic glucosylation were studied. The addition of a suitable amount of ILs including denaturing ones was favorable to shift the reaction equilibrium toward the synthesis, thus improving the yields. Among the examined ILs, the novel IL [BMIm]I proved to be the best. And this IL was applied as the solvent in biocatalysis for the first time. The yields were found to be enhanced between 0.2-fold and 0.5-fold after the addition of 10% (v/v) [BMIm]I. In 10% (v/v) [BMIm]I-containing system, the desired arylalkyl β-d-glucopyranosides were synthesized with 15–28% yields, among which salidroside was obtained with a yield of 22%.