Niki E
Research Center for Advanced Science and Technology, University of Tokyo, Japan.
Am J Clin Nutr. 1991 Dec;54(6 Suppl):1119S-1124S. doi: 10.1093/ajcn/54.6.1119s.
Free radicals attack lipids, proteins, enzymes, and DNA to cause pathological events and cancer. Ascorbic acid is one of the strongest reductants and radical scavengers and reduces stable oxygen, nitrogen, and thyl radical and acts as a primary defense against aqueous radicals in the blood. When radicals were formed in aqueous suspensions of erythrocytes or low-density lipoprotein (LDL), ascorbic acid scavenged radicals before they reached membranes and LDL. Although ascorbic acid cannot scavenge lipophilic radicals within the lipid compartment by itself, it acts as a synergist with tocopherol for the reduction of lipid peroxyl radicals within the lipid compartment by reacting with tocopheroxyl radical and regenerating active tocopherol. Ascorbic acid may act as a prooxidant in vitro in the presence of metal, but this effect is unlikely to be important in vivo where metal ions are sequestered and other reductants are present.
自由基攻击脂质、蛋白质、酶和DNA，从而引发病理事件和癌症。抗坏血酸是最强的还原剂和自由基清除剂之一，能还原稳定的氧、氮和硫自由基，并作为血液中水性自由基的主要防御物质。当在红细胞或低密度脂蛋白（LDL）的水悬浮液中形成自由基时，抗坏血酸在自由基到达细胞膜和LDL之前将其清除。虽然抗坏血酸本身不能清除脂质区室中的亲脂性自由基，但它与生育酚协同作用，通过与生育酚氧基自由基反应并再生活性生育酚，来还原脂质区室中的脂质过氧自由基。在有金属存在的情况下，抗坏血酸在体外可能充当促氧化剂，但在体内金属离子被螯合且存在其他还原剂的情况下，这种作用不太可能很重要。
