Enzymatic synthesis of palm-based ascorbyl esters

摘要

The synthesis of palm-based ascorbyl esters through transesterification of ascorbic acid and palm oil in tert-amyl alcohol catalyzed by immobilized lipase is described. Highest conversion (70-75%) was determined after 16 h reaction at 40 C using lipase (Novozyme 435 from Candida antartica) with an ascorbic acid to palm oil mole ratio of 1:8. The purified product was further characterized by ~(13)C NMR and GC-MS and the mixture of ascorbyl monoesters obtained were identified as ascorbyl monooleate (61%), ascorbvl monopalmitate (30%) and ascorbyl monostearate (9%). The antioxidant activity of palm-based ascorbyl esters was evaluated by 1,1-diphenyl-2-picrylhydrazyl (DPPH) test. The results showed that pure palm-based ascorbyl esters have an antioxidant activity with an IC50 value of 0.1 mg/mL.