Enzymatic Synthesis of a Novel Antioxidant Octacosanol Lipoate and Its Antioxidant Potency in Sunflower Oil.

α-Lipoic acid possesses remarkable antioxidant activity; however, its poor lipid solubility greatly restricts its practical utilization. The present study was the first (i) to synthesize a novel lipophilic antioxidant of octacosanol lipoate and (ii) to assess its antioxidant potency in sunflower oil by hydrogen nuclear magnetic resonance (1H NMR) spectroscopy. In brief, octacosanol lipoate was successfully synthesized using octacosanol and lipoic acid as substrates and Candida sp. 99-125 lipase as a catalyst. The conversion of octacosanol lipoate could reach as high as 98.1% within merely 2 h, with an overall yield of 87.9%. The hydrophobicity of lipoic acid was significantly enhanced upon esterification with octacosanol. Interestingly, both traditional methods and 1H NMR analysis consistently indicated that octacosanol lipoate exhibited superior antioxidant activity compared with butyl hydroxytoluene at high temperatures. It was concluded that octacosanol lipoate has the potential to be developed into a safe and efficient natural antioxidant which can be utilized not only in daily cooking oils but also in frying oils.