原儿茶酸烷基酯在水包油乳液中的抗氧化行为

Antioxidant Behavior of Protocatechuic Acid Alkyl Esters in Oil-in-water Emulsion

以原儿茶酸(PA)和系列正烷基醇为原料,采用直接酯化法合成了4种PA烷基酯。用IR和1HNMR表征了其结构,用DPPH法和ABTS法测定了其自由基清除能力,用Schaal烘箱实验考察了其在水包油乳液中的抗氧化效率。结果表明,PA酯化后增强了其对自由基的清除能力,并且随着烷基链长的增加清除能力增强。PA酯化提高了其在水包油乳液中的抗氧化效率,并随烷基链长的增加,抗氧化效率先增大后下降,原儿茶酸辛酯的抗氧化效率最佳。各种PA烷基酯在乳化剂吐温20的体积分数为4%、油与水体积比2∶8的菜籽油乳液中的抗氧化效率最佳。与添加PA的乳液相比,添加PA烷基酯的乳液的共轭二烯含量(CD)值达到1的时间以及p-茴香胺含量(AV)值达到6的时间均显著增加。

Four protocatechuic alkyl esters were synthesized by direct esterification reaction with protocatechuic acid and a series of alkyl alcohols as raw materials, and their structures were identified by infrared and 1 HNMR spectroscopy. DPPH assay and ABTS assay were used to determine their free radical scavenging capacity. The Schaal oven test was used to determine their antioxidant efficiency in oil-in-water emulsion. The results showed that the free radical scavenging capacity of protocatechuic acid alkyl esters was higher than that of PA, and it increased with the increase of alkyl chain length. Esterification of protocatechuic acid enhanced its antioxidant activity in the oil-in-water emulsion. As the alkyl chain length increased, the antioxidant efficiency first increased and then decreased. Octyl protocatechuate showed the best maximum antioxidant efficiency. The maximum of antioxidant efficiency of all protocatechuic alkyl esters was obtained when the volume fraction of emulsifier was 4% in rapeseed oil emulsions with oil to water volume fraction 2∶8. For the emulsions containing protocatechuic alkyl esters, the time of the conjugated diene value to reach 1 and the time of p-anisidine value to reach 6 were obviously improved compared with those of the emulsion using protocatechuic acid as emulsifier.