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Polar paradox revisited: analogous pairs of hydrophilic and lipophilic antioxidants in linoleic acid emulsion containing Cu( II )
Author(s) -
Bakır Temelkan,
Sönmezoğlu İnci,
İmer Filiz,
Apak Reşat
Publication year - 2013
Publication title -
journal of the science of food and agriculture
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.782
H-Index - 142
eISSN - 1097-0010
pISSN - 0022-5142
DOI - 10.1002/jsfa.6063
Subject(s) - chemistry , trolox , ascorbic acid , gallic acid , propyl gallate , tbars , antioxidant , hydroquinone , ascorbyl palmitate , emulsion , thiobarbituric acid , organic chemistry , lipid peroxidation , linoleic acid , medicinal chemistry , food science , fatty acid , antioxidant capacity
Background Literature data are scarce on the activities of analogous pairs of hydrophilic and lipophilic antioxidants related to the ‘polar paradox’ distinguishing antioxidants based on their partitioning between lipids and water. The peroxidation of linoleic acid ( LA ) in the presence of either Cu( II ) ions alone or Cu( II ) ions combined with Trolox ( TR ), ascorbic acid ( AA ), hydroquinone ( HQ ) and gallic acid ( GA ), as hydrophilic antioxidants, or with α ‐tocopherol ( TocH ), ascorbyl palmitate ( AP ), tert ‐butyl hydroquinone ( TBHQ ) and propyl gallate ( PG ), as their respective lipophilic analogues, was investigated in aerated and incubated emulsions at 37 °C and pH 7 . Results LA peroxidation induced by Cu( II ) followed pseudo‐first‐order kinetics with respect to the formation of primary (hydroperoxides) and secondary (aldehyde‐ and ketone‐like) oxidation products, which were determined by ferric thiocyanate (Fe( III )‐ SCN ) and thiobarbituric acid‐reactive substances ( TBARS ) methods respectively. With the exception of TocH at certain concentrations, the tested compounds showed antioxidant behaviour depending on their polarities. The results were evaluated in the light of structure–activity relationships and the polar paradox . Conclusion The results of this study partly confirm the hypothesis that the polar paradox experiences limitations in oil‐in‐water emulsions and that its validity is also dependent on the concentrations of the antioxidants employed. © 2013 Society of Chemical Industry