The Contribution of d α -Tocopherol and d γ -Tocopherol to the Antioxidant Capacity of Several Edible Plant Oils

Abstract

Many oils from plants are important components of our food chain and maintaining their oxida-tive stability (OS) is economically and nutritionally important. OS is dependent in part on antioxi-dant capacity (AC) arising from the electron donating ability of endogenous compounds in the oils. Attention has focused on the contribution to AC of phenolic compounds in oils as many have bio-activities in vitro. However, the relevance of such phenolics to healthy nutrition remains unclear. In contrast, many plant-derived oils also contain tocopherol homologs, which as vitamin E are di-etary-essential, lipid-soluble antioxidants. We have determined the AC of twelve " off the shelf " edible oils by assessing their ability to quench galvinoxyl, a stable free radical species. The sto-chiometric reactivity of vitamin E with galvinoxyl indicates that the combined dα-tocopherol and dγ-tocopherol homologs contribute between 20% (olive) and 85% (soya) to AC depending on type of oil. Tocopherols are important contributors to the AC of several vegetable oils. Breeding and photo mixotrophic programmes to enhance content in edible oil crops of this important vitamin may have a positive impact not only on oil stability during storage but also in contributing to pro-vision of optimum dietary intakes for health.