Green and efficient synthesis of pine sterol oleate catalyzed by SO3H-functionalized ionic liquid

Background Phytosterol esters can be used in the food industry because of their various physiological activities and better physical properties compared to free phytosterols. However, existing synthetic methods for phytosterol esters tend to have the problems of environment unfriendliness, excessive by-products, and difficulty in product separation and purification. Therefore, it is crucial to develop a green and efficient synthetic process for phytosterol esters. Results The catalytic properties of various SO3H-functionalized ionic liquids for the synthesis of pine sterol oleate were investigated, and [BSO(3)HMIm]Ts showed the best catalytic effect and reaction selectivity. Under the optimized reaction conditions: using 7% of [BSO(3)HMIm]Ts (based on the mass of pine sterols) as the catalyst, the molar ratio of oleic acid to pine sterols 2:1, reaction at 140 degrees C for 2.5 h, the yield of pine sterol oleate could reach 93.9%, while only 4.2% of dehydrated sterols by-products could be produced. Furthermore, the esterification yield could still reach 85.0% after the catalyst [BSO(3)HMIm]Ts was reused six times under the optimal conditions. Conclusion This study demonstrates that SO3H-functionalized ionic liquid [BSO(3)HMIm]Ts has higher catalytic activity and selectivity than many reported chemical catalysts in the synthesis of phytosterol esters. A green, efficient, and scalable procedure for the esterification of phytosterols with fatty acids in a solvent-free system has been developed. (c) 2022 Society of Chemical Industry (SCI).