Antioxidant/prooxidant effects of α-tocopherol, quercetin and isorhamnetin on linoleic acid peroxidation induced by Cu(II) and H₂O₂

Abstract

The peroxidation of linoleic acid (LA) in the presence of copper(II) (Cu(II)) ions alone and with α-tocopherol (α-TocH) was investigated in aerated and incubated emulsions at 37 °C and pH 7. Additionally, the effects of quercetin (QR) and its O-methylated derivative, isorhamnetin (IR), as potential antioxidant protectors were studied in the (Cu(II) + TocH)-induced LA peroxidation system. Cu(II)-induced LA peroxidation followed pseudo-first-order kinetics with respect to primary (hydroperoxides) and secondary (aldehydes- and ketones-like) oxidation products, which were determined by ferric thiocyanate and thiobarbituric acid-reactive substances methods, respectively. As opposed to the concentration-dependent (at 0.6 and 10.0 µM) prooxidative action of α-TocH in the absence of QR and IR, the latter two compounds showed antioxidant effect over TocH. The peroxidation of LA in the presence of Cu(II)−H₂O₂ combination alone and with TocH, QR and IR were also investigated in aerated and incubated emulsions, where the latter three compounds exhibited antioxidant effects.

• Copper-initiated prooxidant activity
• hydroperoxides
• isorhamnetin
• linoleic acid peroxidation
• quercetin
• tocopherol

Declarations of interest

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.

This work was supported by Yildiz Technical University, Research Fund, YTÜ-BAPK Project No: 29-01-02-03. One of the authors (Dr. Apak) would like to thank T.R. Ministry of Development for the Advanced Research Project of Istanbul University (2011K120320).