Efficient synthesis of phytosteryl esters using the Lewis acidic ionic liquid

Phytosteryl esters are of significant importance due to their recent recognition and contribution as cholesterol-lowering agents in food and nutrition. The synthesis of phytosteryl esters from phytosterols and fatty acids in the presence of ionic liquids with high yield and purity was investigated. Six common ionic liquids, including [Bmim]BF4, [Bmim]CF3SO3, ChCl·2SnCl2, ChCl·2ZnCl2, ChCl·2.5SnCl2 and ChCl·2FeCl3, were evaluated to determine the satisfactory catalyst for the esterification, and the results showed that ChCl·2SnCl2 was the most suitable catalyst in this study. Moreover, it was found that the catalytic activity of ionic liquids for the esterification enhanced with the increase of their Lewis acidity, which was determined by pyridine as IR spectroscopic probe. The reaction conditions were further surveyed and the experimental esterification rate reached a greatly high level of 92.3% using ChCl·2SnCl2 as catalyst with the molar ratio 3:1 (lauric acid:plant sterols) at 150 °C for 4 h. FT-IR, MS, and NMR analyses were adopted to evaluate the synthesized phytosteryl laurate. And also the physiochemical property of phytosterols and phytosteryl laurate was compared, suggesting that phytosteryl ester favored its wide application in fatty based food.

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► Ionic liquids used in catalysis were selected in the esterification of phytosterol and fatty acids.
► Esterification degree showed an increasing trend with increasing in Lewis acidity of the ionic liquids.
► The ionic liquid exhibited excellent catalytic activity and reusability.