Ascorbic acid

February 15, 2021
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L-Ascorbic acid, more familiarly known as vitamin C, is widely found in nature. It is particularly abundant in citrus and stone fruits, berries (especially acerola), peppers, and green vegetables.

Ironically ascorbic acid was first isolated from an animal source. In 1928, the legendary Hungarian biochemist Albert Szent-Györgyi, then a student at the University of Cambridge (UK), extracted what he called “hexuronic acid” from the adrenal cortices of oxen. He and colleague Walter Norman Haworth later isolated the molecule from lemons and paprika. Szent-Györgyi was awarded the Nobel Prize in Physiology or Medicine in 1937; the same year, Haworth received the prize in chemistry.

In 1933, R. G. Ault at Birmingham Chemical Laboratories (UK), along with Haworth and others, was the first to report a synthesis of L- and D-ascorbic acid. (The D-enantiomer does not exist in nature and has no known uses.) That same year, Polish chemist Tadeusz Reichstein and colleagues at ETH Zürich developed a robust chemical/microbial process for producing ascorbic acid from D-glucose. Their multistep process was the predominant manufacturing route until the 1960s, when it was displaced by a two-step fermentation process in developed in China. Reichstein was awarded the 1950 Nobel Prize in Physiology or Medicine, but for his work on cortisone, not ascorbic acid.

Vitamin C, as ascorbic acid or its salts, is essential for human nutrition. It is a cofactor that permits several enzymes to function properly; it plays a role in the immune system; and it is an antioxidant. Vitamin C deficiency causes the disease scurvy, which, if not treated, results in decreased red blood cell production and excessive bleeding. In extreme cases, it is fatal.

Ascorbic acid, as vitamin C, was the topic of much controversy in the 1970s. Double Nobel prizewinner Linus Pauling advocated the consumption of large doses of the vitamin as a way to compensate for the body’s inability to produce enough of it for optimum health. Specifically, Pauling espoused taking 2.5 g or more vitamin C per day for general health and to prevent or treat the common cold. He and others also contended that doses as great as 10 g/day helped prevent or cure heart disease and cancers. The so-called vitamin C megadose theory has been largely discredited. 

Originally the Molecule of the Week for January 1, 2007

Ascorbic acid hazard information

Hazard class*Hazard statement
Not a hazardous substance or mixture 

*Globally Harmonized System of Classification and Labeling of Chemicals.  

Molecule of the future

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Molecule of the Future: EC5026

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Ascorbic acid fast facts

CAS Reg. No.50-81-7
L-Ascorbic acid
Empirical formulaC6H8O6
Molar mass176.12 g/mol
AppearanceWhite to pale yellow crystals or powder
Melting point190–192 ºC (dec)
Water solubility330 g/L

MOTW update

Squalene was the Molecule of the Week for December 14, 2020. It is a natural isoprenoid that is an intermediate in the biosynthesis of all animal and plant steroids, including cholesterol. It is most abundant in fish liver oils. In a recent study of ozone pollution, Yingjun Ping at Peking University (Beijing) and international colleagues found that squalene plays a significant role in determining the concentration of ozone inside residences. Squalene is a major component of human skin oils; and the authors found that its reaction products with ozone were abundant in the home that they studied. The concentration of squalene ozonation products correlated with the number of people in the home at any given time.


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