Electron Spin Resonance Spin Trapping for Analysis of Lipid Oxidation in Oils:  Inhibiting Effect of the Spin Trap α-Phenyl-N-tert-butylnitrone on Lipid Oxidation

Abstract

The electron spin resonance (ESR) spin trapping technique was investigated as an analytical approach to follow lipid oxidation of rapeseed oil, sunflower oil, and fish oil during storage at 40 degrees C. Unlike previous investigations, alpha-phenyl-N-tert-butylnitrone (PBN), used as spin trap, was added to the fresh oils and formation of radicals was monitored during storage. Results were compared with the development in peroxide value (PV) and the thiobarbituric acid index (TBA). Increasing radical development was detected during the initial stages of oxidation, during which no significant changes in PV and TBA were observed. Evidence of spin adduct depletion was found during prolonged storage, suggesting that although spin trapping of radicals may be used to follow early events in lipid oxidation, it is not a suitable parameter for long periods of time. Addition of the spin trap after sequential samplings is recommended for getting an insight of oxidative changes during storage. Further, the influence of the spin trap (PBN) on lipid oxidation was studied in detail by application of PV and TBA and by following the depletion of naturally occurring tocopherol. PBN was found to possess a profound inhibiting effect on lipid oxidation. Such an effect was found to be dependent on the nature of the oil, and it was observed that the lower the oxidative stability, the larger the effect of PBN on lipid oxidation. This effect was interpreted in terms of the capability of PBN to react with peroxyl radicals, which in turn depends on the initial tocopherol content of the oils.

Oxidative stability and radical scavenging activity of extra virgin olive oils: An electron paramagnetic resonance spectroscopy study

“…Among several 43 nitrones used as spin traps, N-t-butyl-␣-phenylnitrone (PBN) 44 was preferred due to its lipophilic character and the stability of 45 the resulting spin adducts [8]. PBN has been successfully used 46 as a spin trap for the entrapment of lipid free radicals in food 47 lipids [9], vegetable oils and their mixtures [10], mayonnaise 48 [11] and fish oil [12].…”

Trends in Edible Vegetable Oils Analysis. Part A. Determination of Different Components of Edible Oils – A Review

“…The induction period in such samples can be indicated with the use of differential scanning calorimetry (DSC) in an isothermal stream (heat flux), with a continuous oxygen stream [Giuffrida et al, 2007]. However, the generation of free radicals can be observed with electron spin resonance spectroscopy (ESR) using N-tert-butyl-α-phenylnitrone dissolved in an oil sample as a spin trap [Velasco et al, 2005]. Both methods are also widely used in analysis of the activity and stability of antioxidants in high temperatures [Giuffrida et al, 2007].…”

Antioxidative and Anticorrosive Properties of Bioglycerol

“…Naturally occurring antioxidants in oils belong mainly to the group of tocopherols. α-Tocopherol is considered to be predominant antioxidant in olive and sunflower oils (Velasco et al, 2005, Blekas et al, 1995, Koski et al 2002 while -tocopherol prevails in rapeseed oil (Velasco et al, 2005, Koski et al 2002. The content of antioxidants depends also on the type of oil purification procedures (cold-pressed, refined).…”

“…The antioxidants occurring in the transesterification products should have phenolic-like structure due to their vegetable oil origin. Virgin oils are rich in substances that exert antioxidant properties such as: tocopherols, phospholipids, carotenes and sterols (Velasco et al, 2005, Blekas et al, 1995, Koski et al 2002. Chemical properties of the tocopherols lead to their better solubility in bioglycerol than biodiesel.…”