Enzymatically derived oil-based L-ascorbyl esters: Synthesis, antioxidant properties and controlled release from cosmetic formulations

Abstract

Lipase-catalyzed transesterification of vitamin C by natural triglycerides is promising approach for cost-efficient synthesis of liposoluble food and cosmetic antioxidants. Nevertheless, application of these alternative acyl donors is insufficiently explored, despite of their low price, wide abundance and possibility for obtaining versatile products. Within current study, fatty acid ascorbyl esters were synthesized from vitamin C and natural triglycerides (lard, sunflower, coconut and linseed oil) in a process catalyzed by immobilized lipase Novozym® 435 and their controlled release was examined. High conversions were achieved at optimized conditions, even at high substrate concentrations, thus high concentrations of acsorbyl-ester were synthesized using these natural lipids. All ester mixtures exhibited very high capacity for scavenging of DPPH radicals, among which linseed oil derived esters, with ascorbyl linolenate as prevailing compound, were the most efficient (IC50 0.663 μM), while coconut oil derived ester mixture (IC50 0.739 μM), composed predominantly of molecules with medium side chains, was second best. Coconut oil derived esters were successfully incorporated in typical cosmetic formulations for controlled release of bioactive compounds - O/W emulsion and gel-emulsion. Franz cell diffusion study demonstrated that esters release from mixture and two carrier systems was formulation dependent and revealed decrease of effective diffusivities with ester side acyl chain length increase. According to calculated effective diffusivity coefficients, faster trans-membrane delivery of the same molecule was achieved from gel-emulsion comparing to O/W emulsion. Applied approach enabled highly efficient cost-saving production of fatty acid ascorbyl esters, which could find direct application in various lipophilic products.