chapter  14
36 Pages

- Ascorbic Acid

Ascorbic acid (vitamin C) plays a role as a redox cofactor and catalyst in a broad array of biochemical reactions and processes. Vitamin C is designated as ascorbic acid because of its ability to cure and prevent scurvy [1-6]. Descriptions of scurvy rst appeared in Egyptian medical scrolls, although it was over 3000 years later that a connection between scurvy and diet was clearly established and an

14.1 Introduction and History ...................................................................................................... 515 14.2 Chemistry and Food Sources ................................................................................................ 516

14.2.1 Nomenclature and Structure ..................................................................................... 516 14.2.2 Physical and Chemical Properties ............................................................................ 516 14.2.3 Chemical and Biological Synthesis .......................................................................... 518 14.2.4 Analysis .................................................................................................................... 519 14.2.5 Sources of Ascorbic Acid ......................................................................................... 521

14.3 Biochemical Functions ......................................................................................................... 521 14.3.1 Plants......................................................................................................................... 521 14.3.2 Animals and Animal Models ................................................................................... 522 14.3.3 Selected Enzymes and Biochemical Processes ........................................................ 523

14.3.3.1 Ascorbic Acid and Glutathione Interrelationships ..................................... 523 14.3.3.2 Norepinephrine and Adrenal Hormone Synthesis ..................................... 524 14.3.3.3 Hormone Activation (α-Amidations) ......................................................... 525 14.3.3.4 Ascorbic Acid as an Antioxidant ............................................................... 525 14.3.3.5 Carnitine Biosynthesis ............................................................................... 527 14.3.3.6 Extracellular Matrix and Ascorbic Acid .................................................... 527 14.3.3.7 Ascorbic Acid and Gene Expression ......................................................... 529

14.4 Ascorbic Acid Metabolism and Regulation .......................................................................... 530 14.5 Clinical Features Important to Ascorbic Acid Status ........................................................... 531

14.5.1 Dening Ascorbic Acid Status ................................................................................. 531 14.5.2 Clinical Features ....................................................................................................... 531

14.5.2.1 Immune Function ....................................................................................... 531 14.5.2.2 Progression of Chronic Diseases ............................................................... 533

14.6 Requirements, Allowances, and Upper Limits ..................................................................... 536 14.6.1 Rebound Scurvy ....................................................................................................... 536 14.6.2 Exercise Performance ............................................................................................... 537 14.6.3 Oxalic Acid and Uric Acid ....................................................................................... 537 14.6.4 Iron-Related Disorders ............................................................................................. 537 14.6.5 Vitamin B12 ............................................................................................................... 538

14.7 Summary .............................................................................................................................. 538 References ...................................................................................................................................... 538

additional 100 years before the rst biological and chemical descriptions of ascorbic acid began to appear [1]. Ascorbic acid comes from the Scandinavian terms, Skjoerberg or Skorbjugg, and from the English terms, Scarfy or Scorby. From a historical perspective, it is instructive to visit the original treatise on scurvy by James Lind, Treatise on the Scurvy, published in 1753 [7].