Talcott R E, Smith M T, Giannini D D
Arch Biochem Biophys. 1985 Aug 15;241(1):88-94. doi: 10.1016/0003-9861(85)90365-0.
Menadione (2-methyl-1,4-naphthoquinone) is a remarkably potent inhibitor of microsomal lipid peroxidation, effective at submicromolar concentrations. Its possible mechanism of action and the relationship between naphthoquinone structure and antioxidant activity were the topics of this investigation. In the microsomal lipid-peroxidizing system dependent on NADPH and ferric pyrophosphate, menadione, at concentrations of 50 microM or higher virtually eliminated the accumulation of malondialdehyde and lipid hydroperoxides. In the NADPH-independent, cumene hydroperoxide-dependent system, menadione was also an effective antioxidant, but only in the presence of reducing equivalents. These and other observations indicate that a reduced form of menadione, either the hydroquinone or semiquinone, is the active antioxidant, and suggest that it may trap hydroperoxy radicals, alkoxy radicals, or other free radicals involved in propagating lipid peroxidation. Moreover, these results show that electron diversion per se cannot account for the antioxidant effects of menadione. A comparison of the antioxidant activities of eight 1,4-naphthoquinones indicated that methyl substitution of C-2, lack of steric hindrance at C-3 or C-5, and (in the case of weak acids) a relatively high pKa are favorable structural features associated with strong antioxidant activity.
甲萘醌（2-甲基-1,4-萘醌）是一种非常有效的微粒体脂质过氧化抑制剂，在亚微摩尔浓度下即可发挥作用。本研究的主题是其可能的作用机制以及萘醌结构与抗氧化活性之间的关系。在依赖于NADPH和焦磷酸铁的微粒体脂质过氧化系统中，浓度为50微摩尔或更高的甲萘醌几乎完全消除了丙二醛和脂质氢过氧化物的积累。在不依赖NADPH、依赖氢过氧化异丙苯的系统中，甲萘醌也是一种有效的抗氧化剂，但仅在存在还原当量的情况下。这些及其他观察结果表明，甲萘醌的还原形式，即对苯二酚或半醌，是活性抗氧化剂，并表明它可能捕获参与脂质过氧化传播的氢过氧自由基、烷氧自由基或其他自由基。此外，这些结果表明，电子转移本身并不能解释甲萘醌的抗氧化作用。对八种1,4-萘醌的抗氧化活性进行比较表明，C-2位的甲基取代、C-3或C-5位不存在空间位阻，以及（对于弱酸而言）相对较高的pKa是与强抗氧化活性相关的有利结构特征。
