Studies on the enzymatic synthesis of lipophilic derivatives of natural antioxidants

The esterification of some natural antioxidants such as cinnamic acid derivatives and ascorbic acid in nonaqueous media, catalyzed by immobilized lipases from Candida antarctica and Rhizomucor miehei was investigated. The alcohol chain length affected the rate of esterification of cinnamic acids by both lipases. Higher reaction rates were observed when the esterification was carried out with medium- or long-chain alcohols, The rate also depended on aromatic acid structure. The reactivity of the carboxylic function of the cinnamic acids was affected by electron-donating substituents in the aromatic ring. Higher yields were observed for the esterification of p-hydroxyphenylacetic acid (97%) catalyzed by C. antarctica lipase and for the esterification of cinnamic acid (59%) catalyzed by R. miehei lipase. Candida antarctica lipase was more suitable for-producing ascorbic acid fatty esters, catalyzing with a relatively high yield (up to 65% within 24 h) the regioselective esterification of ascorbic acid with various fatty acids in 2-methyl-2-propanol. The reaction rate and yield depended on the fatty acid chain length and on the molar ratio of reactants. All ascorbic acid fatty esters produced by this procedure exhibited a significant antioxidant activity in a micellar substrate composed of linoleic acid. Paper no. J9139 in JAOCS 76, 1505-1510 (December 1999).