Effects of α‐ and γ‐tocopherols on the autooxidation of purified sunflower triacylglycerols

Abstract

The antioxidant effects of alpha- and gamma-tocopherols were evaluated in a model system based on the autooxidation of purified sunflower oil (p-SFO) triacylglycerols at 55 degrees C for 7 d. Both tocopherols were found to cause more than 90% reduction in peroxide value when present at concentrations >20 ppm. Alpha-tocopherol was a better antioxidant than gamma-tocopherol at concentrations < or =40 ppm but a worse antioxidant at concentrations >200 ppm. Neither alpha- nor gamma-tocopherol showed a prooxidant effect at concentrations as high as 2000 ppm. The amount of tocopherols consumed during the course of oxidation was positively correlated to the initial concentration of tocopherols, and the correlation was stronger for alpha- than for gamma-tocopherol. This correlation suggested that, besides reactions with peroxyl radicals, destruction of tocopherols may be attributed to unknown side reactions. Addition of FeSO4, as a prooxidant, caused a 12% increase in the peroxide value of p-SFO in the absence of tocopherols. When tocopherols were added together with FeSO4, some increase in peroxide value was observed for samples containing 200, 600 or 1000 ppm of alpha- but not gamma-tocopherol. The addition of FeSO4, however, caused an increase in the amount of alpha- and gamma-tocopherols destroyed and led to stronger positive correlations between the amount of tocopherols destroyed during oxidation and initial concentration of tocopherols. No synergistic or antagonistic interaction was observed when alpha- and gamma-tocopherols were added together to autooxidizing p-SFO.

Evaluation of the Antimicrobial and Antioxidant Activities of Origanum dictamnus Extracts before and after Encapsulation in Liposomes

“…The antioxidant (pure extract in concentrations 120 and 240 ppm, BHT and α-tocopherol both at 150 ppm -Sigma Chemicals Company Ltd., St. Louis, USA) was accurately weighed into stripped sunflower oil (Elais S.A., Athens, Greece) prepared using the method described by Fuster et al [10] and its action was determined using a Rancimat 679 (Metrohm LTD, Herisau, CH 9101, Switzerland), along with another sample of sunflower oil without antioxidant (control). One mL of the appropriate solvent (MeOH or CH 2 Cl 2 ) was added in order to dissolve the antioxidant.…”

“…Stripped sunflower oil (10 g, prepared using the method described by Fuster et al [10]) and added antioxidant (pure extract, BHT, α-tocopherol in concentrations of 100 and 150 ppm) were accurately weighed into a glass Petri dish (87 mm internal diameter and 15 mm in height) and mixed well. The dishes were placed (half immersed) in a water bath (50 °C) directly exposed to UV light produced by a lamp situated 50 cm above (General Electric 260 nm UV Germicidal lamp G25T8, 25 Watt, 45 cm in length and 3 cm in diameter) for 12 hours.…”

Commercial Cold Pressed Flaxseed Oils Quality and Oxidative Stability at the Beginning and the End of Their Shelf Life

“…Nogala-Ka ucka et al 42 found that γ-tocopherol has the best protective properties at temperature of 4 in comparison to other tocopherols. The most effective antioxidant activity with respect to triacylglycerols TAG this homologue exhibits at concentration of 0.01 w/w 42,43 . In turn, α-tocopherol has strong antioxidant activity in the human body, while the activity of β, γ and Δ homologues is limited because they are immediately metabolized in the liver and excreted in the bile or urine 44 .…”

Autoxidation of Conjugated Linoleic Acid Methyl Ester in the Presence of α‐Tocopherol: The Hydroperoxide Pathway

“…This effect has been described as a pro-oxidant effect but is better described as loss of antioxidant efficacy at post-optimal concentrations, because it is plausible that not only the concentration of -tocopherol but also of several other chemical species that may participate in the initiation of the oxidation process are above a certain optimal concentration (Fuster et al 1998;Evans JC et al 2002;Kamal-Eldin et al 2008). For example, the pro-oxidant property was enhanced, i.e.…”