Patil G S, Cornwell D G
J Lipid Res. 1978 May;19(4):416-22.
dl-alpha-Tocopherol spread on an acidic subphase as a gaseous monolayer was oxidized slowly to a derivative that was identified by thin-layer chromatography as alpha-tocopherylquinone. The derivative generated the same II-A isotherm as alpha-tocopherylquinone. When the subphase contained gold chloride, alpha-tocopherol was oxidized rapidly and quantitatively to alpha-tocopherylquinone. dl-alpha-Tocopherol spread on a basic subphase as a gaseous monolayer was oxidized slowly to a mixture that contained alpha-tocopherol, a quinone, and a nonpolar derivative. The mixture generated a II-A isotherm with an inflection point below the equilibrium spreading pressure of either alpha-tocopherol or alpha-tocopherylquinone. When potassium ferricyanide was added to the alkaline subphase, alpha-tocopherol was oxidized rapidly to a mixture that contained both the nonpolar derivative (major product) and the quinone (minor product). The nonpolar derivative was isolated by thin-layer chromatography and identified as the spirodienone ether by ultraviolet, infrared, and chemical ionization mass spectra. The spirodienone ether had a low equilibrium spreading pressure that explained the inflection point in the II-A isotherm generated by alpha-tocopherol on an alkaline subphase. Surface area data showed that dl-alpha-tocopherol formed immiscible films with stearyl alcohol and miscible films with oleyl alcohol. II-A isotherms showed that alpha-tocopherol in both immiscible and miscible mixtures was oxidized rapidly on an alkaline potassium ferricyanide subphase to the spirodienone ether. Collapse pressure data showed that the spirodienone ether formed an immiscible film with stearyl alcohol and a miscible film with oleyl alcohol. Interfacial oxidation experiments showed that alpha-tocopherol is oxidized either to tocopherylquinone (acidic subphase) or to the spirodienone ether (alkaline subphase). The natural occurrence of both tocopherylquinone and the spirodienone ether suggests that several types of oxidant stress are found in biological systems. One type of oxidant stress may involve the peroxy radical generating tocopherylquinone; a second type may involve hydroxyl radical-hydroxide ion generating the spirodienone ether.
作为气态单分子层铺展在酸性亚相上的dl-α-生育酚会缓慢氧化为一种衍生物，通过薄层色谱法鉴定该衍生物为α-生育醌。该衍生物产生的II-A等温线与α-生育醌相同。当亚相中含有氯化金时，α-生育酚会迅速且定量地氧化为α-生育醌。作为气态单分子层铺展在碱性亚相上的dl-α-生育酚会缓慢氧化为一种混合物，该混合物含有α-生育酚、一种醌和一种非极性衍生物。该混合物产生的II-A等温线在α-生育酚或α-生育醌的平衡铺展压力以下有一个拐点。当向碱性亚相中加入铁氰化钾时，α-生育酚会迅速氧化为一种混合物，该混合物同时含有非极性衍生物（主要产物）和醌（次要产物）。通过薄层色谱法分离出非极性衍生物，并通过紫外、红外和化学电离质谱鉴定为螺二烯酮醚。螺二烯酮醚的平衡铺展压力较低，这解释了α-生育酚在碱性亚相上产生的II-A等温线中的拐点。表面积数据表明，dl-α-生育酚与硬脂醇形成不混溶膜，与油醇形成混溶膜。II-A等温线表明，在不混溶和混溶混合物中的α-生育酚在碱性铁氰化钾亚相上都会迅速氧化为螺二烯酮醚。崩溃压力数据表明，螺二烯酮醚与硬脂醇形成不混溶膜，与油醇形成混溶膜。界面氧化实验表明，α-生育酚要么被氧化为生育醌（酸性亚相），要么被氧化为螺二烯酮醚（碱性亚相）。生育醌和螺二烯酮醚的天然存在表明生物系统中存在几种类型的氧化应激。一种氧化应激可能涉及产生生育醌的过氧自由基；第二种可能涉及产生螺二烯酮醚的羟基自由基 - 氢氧根离子。
