Dhariwal K R, Hartzell W O, Levine M
Laboratory of Cell Biology and Genetics, National Institute of Diabetes, Digestive, and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892.
Am J Clin Nutr. 1991 Oct;54(4):712-6. doi: 10.1093/ajcn/54.4.712.
We investigated whether circulating ascorbic acid in humans is protein bound or free and whether ascorbic acid exists in its reduced form alone as ascorbic acid or in its reduced and oxidized forms as ascorbic acid and dehydroascorbic acid, respectively. Ascorbic acid and dehydroascorbic acid were determined by using HPLC with coulometric electrochemical detection, and protein binding was determined by centrifugal ultrafiltration. Ascorbic acid was free in plasma and serum of normal, healthy volunteers, 10 men and 10 women. Ascorbic acid was detectable only in its reduced form. However, dehydroascorbic acid could be made to appear in samples processed under oxidizing conditions. Because circulating ascorbic acid is free and is detected only as reduced vitamin, ascorbic acid may be available without intermediates for peripheral utilization. Dehydroascorbic acid may not be present in plasma and serum of normal humans unless assay conditions permit ascorbic acid oxidation.
我们研究了人体中循环的抗坏血酸是与蛋白质结合还是游离状态，以及抗坏血酸是否仅以抗坏血酸的还原形式存在，还是分别以抗坏血酸的还原形式和脱氢抗坏血酸的氧化形式存在。使用带库仑电化学检测的高效液相色谱法测定抗坏血酸和脱氢抗坏血酸，通过离心超滤法测定蛋白质结合情况。在10名男性和10名女性正常、健康志愿者的血浆和血清中，抗坏血酸呈游离状态。抗坏血酸仅以还原形式可检测到。然而，在氧化条件下处理的样品中可使脱氢抗坏血酸出现。由于循环中的抗坏血酸是游离的，且仅作为还原型维生素被检测到，抗坏血酸可能无需中间产物即可用于外周利用。除非检测条件允许抗坏血酸氧化，否则正常人体内的血浆和血清中可能不存在脱氢抗坏血酸。
