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Lipase‐catalyzed regioselective synthesis of flavone C‐glucosides esters and high‐efficiency oil‐soluble antioxidant of bamboo leaves (eAOB‐o)

Liu, Lingyi, Pang, Meirong, Zhang, Ying
European journal of lipid science and technology 2015 v.117 no.10 pp. 1636-1646
acylation, antioxidant activity, antioxidants, bamboos, carboxylic ester hydrolases, equations, fatty acid esters, hydrophobicity, leaves, lipids, solubility, solvents, water content, China
AOB‐w is a water‐soluble antioxidant extracted from bamboo leaves, containing four flavone C‐glucosides (orientin, isoorientin, vitexin, and isovitexin) as functional components. Flavone C‐glucoside esters were firstly synthesized by three lipases (CALB, RM IM, and TL IM) in organic solvent system or solvent‐free system. Results indicated that C12 fatty acid ester exhibited the optimal antioxidant capacity, CALB was the most efficient lipase in both systems, and higher conversion yields were achieved in solvent‐free system. Highest conversion was obtained with 1% water content for CALB and 2% water content for RM IM and TL IM. All lipases displayed absolute 6″‐regioselectivities with monoester. It is required to consider both of hydrophobicity and antioxidant capacity to prepare high‐efficiency oil‐soluble antioxidant. Regression equations were built up to illuminate the relationship between conversion yield of flavone C‐glucoside and antioxidant capacity of its corresponding ester. Highest antioxidant capacity could be achieved when conversion yield was nearly 60% for flavone C‐glucosides. Based on reaction parameters of flavone C‐glucosides, high‐efficiency eAOB‐o was prepared, which could be expected as an excellent oil‐soluble antioxidant in lipids. Practical applications: Water‐soluble antioxidant of bamboo leaves (AOB‐w) is a natural food antioxidant extracted from bamboo leaves, with four flavone C‐glucosides (orientin, isoorientin, vitexin, and isovitexin) as functional components. This study aimed to provide a practical procedure to prepare high‐efficiency lipid antioxidant by enzymatic acylation. Based on the optimal parameters from the synthesis of flavone C‐glucoside esters, high‐efficiency oil‐soluble antioxidant of bamboo leaves (eAOB‐o) was prepared. eAOB‐o exhibited higher antioxidant capacity than cAOB‐o, which has been approved as food antioxidants in China. High‐efficiency acylation products were obtained by consideration both of lipid solubility and antioxidant capacity. Based on the rule, flavone C‐glucoside ester and eAOB‐o were prepared.