Antioxidative ability and mechanism of L-ascorbyl palmitate synthesized by lipases as biocatalyst: Experimental and molecular simulation investigations

Abstract

L-ascorbyl palmitate (L-AP), as a versatile antioxidant, was synthesized from ascorbic acid and palmitic acid with enzymatic synthesis using lipases as biocatalyst, and showed different delayed oxidation effects in different lipids. In this work, the free radical scavenging ability, dispersion, migration and oxygen barrier performance of L-AP were quantitatively analyzed by interaction energy, mean azimuth shift, diffusion coefficient of oxygen, bond dissociation enthalpy (BDE) and frontier molecular orbital analysis. The regeneration effects of L-AP on different tocopherols were further analyzed by Gibbs free energy (ΔG) and degradation of tocopherols during storage. In compared with tocopherols, L-AP and trilinolein cannot bind closely each other and failed to block oxygen penetration in the lipid matrix. The BDE and highest occupied molecule orbital of L-AP indicating that L-AP cannot be used as an effective hydrogen donor to interrupt free radical chain reaction. The ΔG for regeneration reactions of α-, γ-, δ-tocopherol were −1.019, −9.482, −18.151 kJ/mol, respectively, indicating that L-AP was prone to regenerate δ-tocopherol as this combination exhibited the highest antioxidation abilities, which was also reflected from the results that the degradation rates of α- and γ-tocopherol were higher than that of δ-tocopherol.