BACKGROUND
Alpha-lipoic acid has excellent antioxidant activity, but its poor lipid solubility greatly limits its practical application. This study was i) to develop a novel and efficient enzymatic synthesis of lipophilic lipoic acid esters using Candida sp. 99-125 lipase as a catalyst; and ii) to systematically evaluate their antioxidant potential against bulk oil, oil-in-water emulsion (O/W) and cooked ground meat.
RESULTS
Lipophilic lipoic acid esters were successfully and efficiently synthesized using phytosterols as acyl receptor in the presence of Candida sp. 99-125 lipase. The product was identified by MS, FT-IR and NMR as phytosterol lipoate. The maximum conversion of phytosterol lipoate surpassed 90% within 12 h and its final yield exceeded 81%. Interestingly, the oil solubility of lipoic acid was increased at least 25-fold and other physicochemical properties were significantly improved. Most importantly, phytosterol lipoate exhibited higher antioxidant activity than lipoic acid in bulk oil, O/W emulsions and cooked ground meat.
CONCLUSION
The antioxidant capacity of lipoic acid can be significantly enhanced by esterification with phytosterols. Therefore, phytosterol lipoate could be further developed as a new antioxidant for use in oil & fat-based foods. This article is protected by copyright. All rights reserved.