Synthesis of vitamin C, natural vitamin C

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Robert Maurer

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L-ascorbic acid occurs naturally as vitamin C; they contain to a significant extent citrus fruits, kiwis, blackberries, peppers, broccoli and rocket.

n these vegetable sources the vitamin C content is around 100 mg per serving. An important quantity, since the daily requirement of L-ascorbic acid for an adult is around 60 mg.

Despite the relative ease with which it is possible to cover these needs abundantly with simple nutrition, the antioxidant properties of vitamin C have contributed to making it one of the most popular and sought after supplements.

According to its supporters, in fact, the food intake is not sufficient to fully enjoy the precious virtues of this vitamin.


The L-ascorbic acid contained in drugs, supplements or added as an additive to various food products, is not extracted directly from natural sources, but synthesized in the laboratory (alternatively it is possible to administer herbal products rich in natural vitamin C). The first to produce "artificial" Vitamin C were the English chemists Sir Walter Norman Haworth and Sir Edmund Hirst, between 1933 and 1934, years in which the Polish chemist Tadeus Reichstein also achieved the same result.

The synthesis process starts from D-glucose and entrusts the various transformation steps to chemical reactions and / or fermentation processes of a microbial nature (bacteria).

Thanks to genetic recombination techniques, strains of Erwinia have been obtained expressing the 2,5-DKG-reductase gene; the enzyme encoded by this gene is able to transform 2,5-diketo-D-gluconic acid (2,5-DKG) (obtained from the bacterial fermentation of glucose) into 2-KLG. Consequently, as shown in the figure, these Erwinia strains are able to directly convert glucose to 2-KLG, eliminating the original need for various chemical processes.

Once obtained, L-ascorbic acid can be salified or esterified with fatty acids. In the first case, the hydrophilicity of the molecule is maintained and its acidity is reduced. In the second, however, a lipophilic substance is obtained and as such can be added to oils and fats to prevent rancidity.

The salts of L-ascorbic acid are generically called "ascorbates" and take the name of the mineral that characterizes them (potassium ascorbate, sodium ascorbate, calcium ascorbate, etc.).

Since there is no structural difference with the food counterpart, the synthetic vitamin C carries out the same biological action as the natural one. Obviously, however, getting 100 mg of vitamin C from a calcium ascorbate tablet is not like eating a large kiwifruit, for example. Although the quantities of vitamin C ingested are roughly the same, kiwifruit - and vegetables in general - in fact contain many other substances with synergistic or otherwise beneficial action for the body.

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