Lipase-catalysed synthesis of erythorbyl laurate in acetonitrile

Erythorbic acid, a stereoisomer of ascorbic acid, has been used as an antioxidant, but has poor lipophilicity. To overcome this problem, lipase-catalysed esterification between erythorbic acid and lauric acid was performed to synthesise the erythorbyl fatty acid ester in acetonitrile; subsequently, the time course of the enzymatic esterification was monitored, using HPLC equipped with RI- and UV-detectors. A steady state was achieved after 8 h, from initiation of the esterification, and the degree of esterification (molar conversion yield) reached 78.5%. After the purification procedure, the product synthesised by immobilised lipase (Novozym® 435) was identified as erythorbyl laurate (6-O-lauroyl-erythorbic acid) by LC-ESI-MS, ¹H, and ¹³C NMR analysis. The results suggest that erythorbyl laurate, produced in this study, could be used as an emulsifier with antioxidant activity to retard oxidation of lipid foods.