Klein E, Weber N
Institute for Biochemistry and Technology of Lipids, H.P. Kaufmann-Institute, Federal Centre for Cereal, Potato and Lipid Research, Piusallee 68, D-48147 Münster, Germany.
J Agric Food Chem. 2001 Mar;49(3):1224-7. doi: 10.1021/jf000725m.
Attacks of thiyl radicals on the double bonds of unsaturated fatty acids lead to stereomutation (cis-, trans-isomerization without double-bond migration) and addition reactions (thioether formation). On the basis of these findings, an in vitro test system has been developed which allows the study of the effectiveness of specific antioxidants in preventing thiyl radical-induced attacks on unsaturated fatty acids. The test involves thermal treatment of a mixture of oleic (cis-9-octadecenoic) acid and 1-tetradecanethiol with the antioxidant, followed by measurement of the extent of formation of the products of stereomutation and addition (i.e., elaidic (trans-9-octadecenoic) acid and isomeric 9(10)-S-tetradecylstearic acids, respectively) by gas chromatography of their methyl esters as a function of antioxidant concentration. Antioxidants such as octyl gallate, ascorbic acid 6-O-palmitate, ubiquinone 50 (coenzyme Q(10)), rac-alpha-tocopherol, and 2,6-di-tert-butyl-4-methylphenol (BHT) were tested for their ability to protect the >C=C< double bond of oleic acid against attacks of thiyl radicals generated from 1-tetradecanethiol by heating. The results show that octyl gallate, ascorbic acid 6-O-palmitate and, to some extent, ubiquinone 50 (coenzyme Q(10)) were highly effective in preventing reactions of free thiyl radicals with oleic acid, whereas rac-alpha-tocopherol and BHT were moderately effective.
硫自由基对不饱和脂肪酸双键的攻击会导致立体异构化（顺式、反式异构化，双键不迁移）和加成反应（硫醚形成）。基于这些发现，已开发出一种体外测试系统，可用于研究特定抗氧化剂在防止硫自由基对不饱和脂肪酸的攻击方面的有效性。该测试包括将油酸（顺式-9-十八碳烯酸）和1-十四烷硫醇的混合物与抗氧化剂进行热处理，然后通过气相色谱法测量其甲酯的立体异构化产物和加成产物（即分别为反油酸（反式-9-十八碳烯酸）和异构化的9(10)-S-十四烷基硬脂酸）的形成程度，作为抗氧化剂浓度的函数。测试了诸如没食子酸辛酯、抗坏血酸6-O-棕榈酸酯、泛醌50（辅酶Q(10)）、消旋α-生育酚和2,6-二叔丁基-4-甲基苯酚（BHT）等抗氧化剂保护油酸>C=C<双键免受加热产生的1-十四烷硫醇硫自由基攻击的能力。结果表明，没食子酸辛酯、抗坏血酸6-O-棕榈酸酯以及在一定程度上泛醌50（辅酶Q(10)）在防止游离硫自由基与油酸反应方面非常有效，而消旋α-生育酚和BHT的效果中等。
