抗氧化剂
化学
乳状液
同系序列
极地的
分配系数
共轭体系
烷基
双水相体系
有机化学
色谱法
水溶液
聚合物
天文
物理
作者
Mickaël Laguerre,Luis Javier López Giraldo,Jérôme Lecomte,Maria‐Cruz Figueroa‐Espinoza,Bruno Baréa,Jochen Weiß,Eric A. Decker,Pierre Villeneuve
摘要
Twenty years ago, Porter et al. (J. Agric. Food Chem. 1989, 37, 615−624) put forward the polar paradox stating among others that apolar antioxidants are more active in emulsified media than their polar homologues. However, some recent results showing that not all antioxidants behave in the manner proposed by this hypothesis led us to investigate the relationship between antioxidant property and hydrophobicity. With a complete homologous series of chlorogenic acid esters (methyl, butyl, octyl, dodecyl, hexadecyl, octadecyl, and eicosyl), we observed in emulsified medium that antioxidant capacity increases as the alkyl chain is lengthened, with a threshold for the dodecyl chain, after which further chain extension leads to a drastic decrease in antioxidant capacity. The antioxidant capacity evaluation in emulsion was possible using a newly developed conjugated autoxidizable triene (CAT) assay, which allows the assessment of both hydrophilic and lipophilic antioxidants. The nonlinear behavior was mainly explained in terms of antioxidant location since it was found from partition analysis that the dodecyl ester presented the lowest concentration in the aqueous phase and also that the quantity of emulsifier drastically changes the partition of antioxidant. In addition, this nonlinear influence was connected to the so-called cutoff effect largely observed in studies using cultured cells. Taken together, these different results allow one to make the proposal of a new scenario of the behavior of phenolic compounds in emulsified systems with special emphasis on the micellization process. Finally, in the CAT system, the polar paradox appeared to be the particular case of a far more global nonlinear effect that was observed here.
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