Antioxidant Mechanism Studies for Food Phenol Based on the Radical Reaction Products with Food Components

断链抗氧化剂的抗氧化过程分为以下两个阶段：1)自由基捕获阶段（S-OO + AH→←SOOH + A） 2)自由基终止阶段（A→非自由基物质）第二阶段是不可逆的，必须产生稳定的自由基终止化合物。该终止化合物的化学结构为阐明断链抗氧化剂的抗氧化机理提供了重要的信息。姜黄素是一种著名的抗氧化活性食品酚。本研究基于自由基终止产物的化学结构对姜黄素的抗氧化机理进行了研究，揭示了姜黄素与过氧自由基反应生成稳定的3环化合物。当姜黄素处于较高浓度时，它提供二聚体作为末端化合物。鼠尾草酸是一种二萜，存在于常见的唇形科草药、鼠尾草和迷迭香中。鼠尾草酸在相关二萜中具有最强的抗氧化能力。鼠尾草酸的11-酚基首先向自由基提供氢，然后在邻位和邻位上第二个脂质过氧基终止自由基。当偶联在12位（邻位）上进行时，它通过几个步骤产生一个野醌。当偶联在14位（对位）进行时，它产生羟基对醌衍生物。一般来说，抗氧化剂在起作用后会失去活性。鼠尾草酸的正醌衍生物无抗氧化活性；然而，我们发现它的溶液显示出强大的抗氧化活性。从醌中恢复抗氧化活性的机制被明确为醌的自氧化还原反应，因此产生的鼠尾草酸有助于醌溶液的强抗氧化活性。

The antioxidation process of the chain-breaking antioxidant is divided into the following two stages : 1) Radical Trapping Stage (S-OO + AH →← SOOH + A) 2) Radical Termination Stage (A → non-radical materials) The second is irreversible and must produce stable radical termination compounds. The chemical structure of such a termination compound would afford important information in order to elucidate the antioxidant mechanism of the chain breaking antioxidant. Curcumin is a famous antioxidatively active food phenol from turmeric. By this research for the antioxidant mechanism based on the chemical structures of the radical termination products, curcumin is revealed to react with a peroxyl radical to afford stable 3-ringed compounds. When curcumin is in a higher concentration, it affords dimers as terminated compounds. Carnosic acid is an abietane diterpene found in the popular Labiatae herbs, sage and rosemary. Carnosic acid has the most powerful antioxidant potency among related diterpenes. The 11-phenolic group of carnosic acid first undergoes hydrogen donation to a radical species and the radical termination takes place next with a second lipid peroxyl radical at the ortho and parapositions. When the coupling proceeds at the 12-position (ortho-position), it affords a carnosic quinone through several steps. When the coupling proceeds at the 14-position (para-position), it affords a hydroxylparaquinone derivative. Generally, antioxidant loses the activity after its work. The orthoquinone derivative of carnosic acid has no antioxidant activity ; however, we found that its solution became to show potent antioxidant activity. The recovery mechanism of the antioxidant activity from the quinone was clarified to be by a self-redox reaction of the quinone, therefore, procuded carnosic acid contributes the strong antioxidant activity of the quinone solution.