Green and efficient synthesis of highly liposoluble and antioxidant L-ascorbyl esters by immobilized lipases

Abstract

L-ascorbyl palmitate (LAP) is the permitted antioxidant used in baby food, but its high commercial demand is suppressed by poor liposolubility. In this paper, a cleaner and more efficient method to synthesize the high-liposoluble and antioxidant unsaturated fatty acid ascorbyl esters (UFAAE) is proposed, based on the enzymatic catalysis using CaLB immobilized on the ordered mesoporous silicon (CaLB@OMS-C8). The results indicated that the maximum catalytic efficiency (CE) in CaLB@OMS-C8 could reach 20.8 M g−1 h−1, thus facilitating the high conversions of 71.8%, 74.1% and 76.8% for L-ascorbyl oleate (LAO), L-ascorbyl linoleate (LAL) and L-ascorbic acid linolenic ester (LALN), respectively. The higher yield of LALN was explained by molecular docking technology as lipase CaLB presented a high binding affinity to linolenic acid (−18.8 kJ/mol) than those to oleic acid (−9.2 kJ/mol) and linoleic acid (−15.4 kJ/mol). By using unsaturated fatty acids as acyl donors, the synthesized UFAAE exhibited a lower melting point, better liposolubility and comparable antioxidant ability compared to LAP. This method to synthesize the high-soluble and antioxidant L-ascorbyl esters by the enzymatic esterification between L-ascorbic acid and unsaturated fatty acids shows great potential as a clean and efficient approach for future industrial production.