{"id":636,"date":"2017-10-26T15:26:29","date_gmt":"2017-10-26T15:26:29","guid":{"rendered":"https:\/\/courses.lumenlearning.com\/sunynutrition\/?post_type=chapter&p=636"},"modified":"2017-11-14T15:31:03","modified_gmt":"2017-11-14T15:31:03","slug":"9-3-vitamin-c","status":"publish","type":"chapter","link":"https:\/\/courses.lumenlearning.com\/suny-nutrition\/chapter\/9-3-vitamin-c\/","title":{"raw":"9.3 Vitamin C","rendered":"9.3 Vitamin C"},"content":{"raw":"
\r\n\r\nVitamin C is well-known for being a water-soluble antioxidant. Humans are one of the few mammals that don't synthesize vitamin C, making it an essential micronutrient. Other mammals that don't synthesize vitamin C include primates, guinea pigs, and other less prevalent species1<\/sup>.\r\n\r\nVitamin C's scientific names are ascorbic acid or ascorbate and the oxidized form is dehydroascorbic acid or dehydroascorbate. The structure of vitamin C is shown below.\r\n
\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"621\"]\"\" Figure 9.31 Structure of ascorbic acid[\/caption]\r\n\r\n<\/div>\r\nWhen ascorbic acid is oxidized, it forms semidehydroascorbate (1 degree of oxidation) and then dehydroascorbate (2 degrees of oxidation). The structure of dehydroascorbic acid is shown below.\r\n
\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"621\"]\"\" Figure 9.32 Structure of dehydroascorbic acid[\/caption]\r\n\r\n<\/div>\r\nThe figure below shows the reaction through which ascorbic acid can stabilize or quench 2 free radicals. The 2 circled hydrogens are lost and replaced by double bonds when ascorbic acid is oxidized to dehydroascorbic acid. Reducing dehydroascorbic acid back to ascorbic acid is the opposite reaction.\r\n
\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"945\"]\"\" Figure 9.33 The oxidation-reduction reaction between ascorbic acid (left) and dehydroascorbic acid (right)2,3<\/sup>[\/caption]\r\n\r\n<\/div>\r\nAscorbic acid is believed to be a part of an antioxidant network (shown below) where it is oxidized to reduce alpha-tocopherol radicals4<\/sup>. Dehydroascorbic acid can be reduced by thioredoxin reductase, a selenoenzyme, to regenerate ascorbic acid.\r\n
\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"1102\"]\"\" Figure 9.34 The theorized antioxidant network[\/caption]\r\n\r\n<\/div>\r\nSubsections:\r\n\r\n9.31 Absorption and Tissue Accumulation of Vitamin C<\/a>\r\n\r\n9.32 Enzymatic Functions<\/a>\r\n\r\n9.33 Vitamin C Deficiency - Scurvy<\/a>\r\n\r\n9.34 Vitamin C Toxicity, Linus Pauling, & the Common Cold<\/a>\r\n\r\n

<\/b>References & Links<\/h3>\r\n\r\n1. Stipanuk MH. (2006) Biochemical, physiological, & molecular aspects of human nutrition. St. Louis, MO: Saunders Elsevier.\r\n\r\n2. http:\/\/en.wikipedia.org\/wiki\/File:Ascorbic_acid_structure.png\r\n\r\n3. http:\/\/en.wikipedia.org\/wiki\/File:Dehydroascorbic_acid.png\r\n\r\n4. Packer L, Weber SU, Rimbach G. (2001) Molecular aspects of alpha-tocotrienol antioxidant action and cell signalling. J Nutr 131(2): 369S-373S.\r\n\r\n<\/div>","rendered":"
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Vitamin C is well-known for being a water-soluble antioxidant. Humans are one of the few mammals that don’t synthesize vitamin C, making it an essential micronutrient. Other mammals that don’t synthesize vitamin C include primates, guinea pigs, and other less prevalent species1<\/sup>.<\/p>\n

Vitamin C’s scientific names are ascorbic acid or ascorbate and the oxidized form is dehydroascorbic acid or dehydroascorbate. The structure of vitamin C is shown below.<\/p>\n

\n
\"\"<\/p>\n

Figure 9.31 Structure of ascorbic acid<\/p>\n<\/div>\n<\/div>\n

When ascorbic acid is oxidized, it forms semidehydroascorbate (1 degree of oxidation) and then dehydroascorbate (2 degrees of oxidation). The structure of dehydroascorbic acid is shown below.<\/p>\n

\n
\"\"<\/p>\n

Figure 9.32 Structure of dehydroascorbic acid<\/p>\n<\/div>\n<\/div>\n

The figure below shows the reaction through which ascorbic acid can stabilize or quench 2 free radicals. The 2 circled hydrogens are lost and replaced by double bonds when ascorbic acid is oxidized to dehydroascorbic acid. Reducing dehydroascorbic acid back to ascorbic acid is the opposite reaction.<\/p>\n

\n
\"\"<\/p>\n

Figure 9.33 The oxidation-reduction reaction between ascorbic acid (left) and dehydroascorbic acid (right)2,3<\/sup><\/p>\n<\/div>\n<\/div>\n

Ascorbic acid is believed to be a part of an antioxidant network (shown below) where it is oxidized to reduce alpha-tocopherol radicals4<\/sup>. Dehydroascorbic acid can be reduced by thioredoxin reductase, a selenoenzyme, to regenerate ascorbic acid.<\/p>\n

\n
\"\"<\/p>\n

Figure 9.34 The theorized antioxidant network<\/p>\n<\/div>\n<\/div>\n

Subsections:<\/p>\n

9.31 Absorption and Tissue Accumulation of Vitamin C<\/a><\/p>\n

9.32 Enzymatic Functions<\/a><\/p>\n

9.33 Vitamin C Deficiency – Scurvy<\/a><\/p>\n

9.34 Vitamin C Toxicity, Linus Pauling, & the Common Cold<\/a><\/p>\n

References & Links<\/b><\/h3>\n

1. Stipanuk MH. (2006) Biochemical, physiological, & molecular aspects of human nutrition. St. Louis, MO: Saunders Elsevier.<\/p>\n

2. http:\/\/en.wikipedia.org\/wiki\/File:Ascorbic_acid_structure.png<\/p>\n

3. http:\/\/en.wikipedia.org\/wiki\/File:Dehydroascorbic_acid.png<\/p>\n

4. Packer L, Weber SU, Rimbach G. (2001) Molecular aspects of alpha-tocotrienol antioxidant action and cell signalling. J Nutr 131(2): 369S-373S.<\/p>\n<\/div>\n\n\t\t\t

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