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Biocatalytic lipophilization of hydroxycinnamic acids was performed in several BF(4)(-) and PF(6)(-) imidazolium ionic liquids using immobilized lipases. The influence of various reaction parameters on the performance of the biocatalytic process was pointed out, using as model reaction the esterification of ferulic acid. The biocatalytic lipophilization strongly depended on the ion composition of ionic liquids used. Conversions and initial reaction rates were significantly higher in PF(6)(-) as compared with BF(4)(-) ionic liquids and commonly used organic solvents. The high enzyme stability and the relative solubility of substrate versus product in PF(6)(-) ionic liquids can account for the improved synthesis of lipophilic ferulates. These lipophilic derivatives, when used at a concentration of up to 400-fold lower than the parental compound, efficiently inhibited the oxidation of isolated LDL, HDL and total serum in vitro. Moreover, it has been shown for the first time that the lipophilic ferulates improve the antioxidant efficiency of the HDL(3c) towards LDL in vitro oxidation.

The effect of storage on the antioxidant activity of pasteurized reconstituted orange juice was studied. Either heat or high pressure was used for pasteurization and total antioxidant activity and ascorbic acid loss were measured during storage at different temperatures (0, 5, 10, 15 °C). The total antioxidant activity of orange juice, calculated as the sum of the activities of different antioxidant compounds, decreased during storage. This was mainly because of loss of ascorbic acid. However, rates of degradation of ascorbic acid were lower for orange juice treated with high pressure and this led to a better retention of its antioxidant activity when compared with juice pasteurized in a conventional way. [ABSTRACT FROM AUTHOR]