Oxidation of Lipids. XIII. Antioxidant Activities of α-, β-, γ-, and δ-Tocopherols

Abstract The antioxidant activities of α-, β-, γ-, and δ-tocopherols were studied. They were all effective as antioxidant in the oxidations of methyl linoleate in homogeneous solution. When one of the four tocopherols was used alone, they were consumed at the same rate and they suppressed the oxidation for the same period. However, the stabilities of chromanyloxyl radicals derived from the corresponding tocopherols varied considerably and decreased in the order α>β≅γ>δ -chromanyloxyl radicals. α-Tocopherol reacts quite rapidly with β-, γ-, and δ-chromanyloxyl radicals to give α-chromanyloxyl radical and β-, γ-, and δ-tocopherols respectively. Accordingly, when the four tocopherols were used together, α-tocopherol was consumed first, then β- and γ-tocopherols were consumed, and δ-tocopherol began to decrease after most of α-, β-, γ-tocopherols were depleted.