Vitaminas C L-askorbo rūgštis 1000 g

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• Modelis: 5904107777610

L-Ascorbic Acid

Nomenclature

General Information

Empirical Formula

C6H8O6

Molar Mass

176.13 g/mol

Appearance

White or almost white, crystalline powder or colorless crystals, darkening in light and air[1]

Identification

CAS Number

50-81-7

PubChem

54670067

DrugBank

DB00126

[show]SMILES

[show]Properties

[show]Hazards

Similar Compounds

Derived Salts

Sodium Ascorbate

Unless otherwise stated, data refers to

standard conditions (25 °C, 1000 hPa)

Medical Classification

ATC

G01 AD03

S01 XA15

A11 GA01

A11 GB01

Multimedia in Wikimedia Commons

Entry in Wiktionary

Crystals of ascorbic acid (vitamin C) photographed with an optical microscope using a special lighting technique - polarization. 100X magnification

Ascorbic acid, vitamin C, E300 (Latin: acidum ascorbicum) – an organic chemical compound from the group of unsaturated polyhydroxy alcohols. It is essential for the functioning of living organisms. For some animals, including humans, it is a vitamin, meaning it must be supplied in the diet. It is also an antioxidant used as a food additive[7].

Table of Contents

1Structure and Chemical Properties

2Occurrence and Synthesis

2.1Biosynthesis

2.2Inability to Synthesize

2.3Production

3Sources in Food

4Role in the Human Body

4.1Effects of Deficiency

4.2Effects of Excess

5Supplementation

5.1Preventing Cancer Development

5.2Cancer Therapy

5.3Cardiovascular Diseases

5.4Chronic Diseases

5.5Common Cold

5.6COVID-19

6Application in the Food Industry

7History

8Notes

9References

Structure and Chemical Properties

It occurs naturally as a compound with the L configuration in the side chain and the D configuration of the furan system. Under the influence of a methanolic solution of NaOH, it undergoes epimerization to erythorbic acid (D-isoascorbic acid, E315), which differs in the configuration of the side chain[8].

L-Ascorbic acid is sometimes incorrectly called "levorotatory vitamin C" due to confusion of the relative configuration with optical activity[9][10]. In reality, L-ascorbic acid rotates the plane of polarized light to the right ([α]20D ≃ +20°). In contrast, D-ascorbic acid is an antioxidant, but otherwise has no biological significance – it does not act as a cofactor, so it is not a vitamin[11][12][13].

Isomers of ascorbic acid:

L-ascorbic acid (R,S) (1a), D-ascorbic acid (S,R) (1b)

L-isoascorbic acid (S,S) (2a), D-isoascorbic acid (R,R) (2b)

The hydroxyl groups in positions 3 and 4 have an acidic character, especially the 4-OH group, whose pKa is 4.17[8]. The anion formed after the dissociation of a proton from the 4-OH group is stabilized by chemical resonance:

It is very unstable and easily decomposes under the influence of oxygen and high temperature[14].

Occurrence and Synthesis

Biosynthesis

L-Ascorbic acid occurs naturally in many plant and animal organisms[7]. In both kingdoms, the substrate for the biosynthesis of this compound is D-glucose, but it proceeds in different ways. In plants, glucose is oxidized at the C-2 position, followed by epimerization of the C-5 atom and further oxidation at the C-1 position. In animals, the metabolic pathway proceeds through glucuronic acid, followed by inversion of the carbon skeleton, as a result of which the C-1 and C-6 atoms of glucose become the C-6 and C-1 atoms of ascorbic acid, respectively[8].

Inability to Synthesize

In a number of animals, including primates, as well as distantly related guinea pigs[7][15][16] or teleost fish (including rainbow trout and carp), ascorbic acid must be supplied in the diet because their bodies do not produce it. In primates, this is due to a mutation in the gene responsible for the production of L-gulono-γ-lactone oxidase (GLO), which in the liver catalyzes the last stage of biosynthesis of ascorbic acid from D-glucose, i.e., oxidation of L-gulonolactone[15][16]. It is estimated that the inactivation of this gene occurred about 60–75 million years ago, shortly after the separation of simians and prosimians[16]. In teleost fish, in addition to mutations in GLO, there are also other mutations that prevent the synthesis of vitamin C; the inability to produce this compound appeared in them about 200 million years ago[16][17][18].

Production

Most of the ascorbic acid produced industrially is manufactured using a method developed in 1934 by Reichstein and Grüssner[19], in which the substrate is also natural D-glucose[8].

Sources in Food

Crystals of ascorbic acid (vitamin C) photographed with an optical microscope. Combined lighting technique - dark field and polarization. 100X magnification

Vitamin C contained in food is one of the most sensitive vitamins to external factors, it is destroyed (oxidation) by high temperature, exposure to light and direct contact with air[20].

Sources of vitamin C in plant products[21]

[show]Product

Content (mg/100 g)

Sources of vitamin C in animal products[21]

[show]Product

Content (mg/100 g)

Role in the Human Body

It is an antioxidant[30][31]. It activates many enzymes[7], facilitates the assimilation of iron[14][30][32], affects the synthesis of corticosteroids[30][31] and some neurotransmitters[31]. It maintains the proper condition of connective tissue[30][33] (it is essential in the synthesis of collagen[14][31][32][33]), strengthens gums and teeth, and kills bacteria that cause tooth decay[32]. It strengthens the body's resistance to infections[14][31][32][33]. It facilitates wound healing[33]. It stabilizes the psyche[32]. It participates in the metabolism of tyrosine. It also has an impact on maintaining the correct oxidative potential in the cell[citation needed].

Studies indicate no effect of taking vitamin C on the risk of developing a cold and a small effect on its duration (shortening the time by 14% for children and 8% for adults). The exception was a group of marathon participants, skiers and soldiers staying in very low temperatures or subjected to intense physical exertion, who observed a 50% reduction in the occurrence of colds when taking 2 g of vitamin C per day[34].

The recommended intake of vitamin C for an adult is from 45 to 90 mg per day[35][36]. Most animal and plant organisms produce this compound. The exceptions are the organisms of primate mammals (including humans), guinea pigs and some species of bats (due to mutation and loss of the enzyme: L-gulonolactone oxidase), which must be supplied from the outside[37].

Effects of Deficiency

Scurvy[7][14][30][31][32][33] (bleeding and ulceration of the gums, tooth loss)[30][33], fragility and rupture of blood vessels[30][31][32], weakened immunity[30][32][33], swollen and painful joints[30], abnormal bone fusion, slow wound healing[31][33].

Western societies consume much more vitamin C in their diet than is necessary to prevent the development of scurvy[38].

Tobacco smokers often suffer from its deficiency, hence the numerous fine wrinkles characteristic of their skin[32].

Effects of Excess

Ascorbic acid is not toxic, but taken in excess (doses above 2 g per day) may cause stomach ailments, nausea, diarrhea, vomiting, skin rash, and reduce immunity after a radical reduction in dose. Usually, however, its excess is excreted from the body in the urine.

Due to the metabolic effect of vitamin C, it is recommended to avoid consuming larger doses of it (i.e. above 500 mg per day) in the case of the occurrence or tendency to form kidney stones, which include calcium oxalate or uric acid. The same recommendation also applies to people suffering from diseases such as hemochromatosis, thalassemia and sideroblastic anemia[39][40][41][42][43]. It is estimated that limited-time intravenous administration of high doses of vitamin C should not increase the risk of urolithiasis[44]. A prospective cohort analysis from 2015 showed that vitamin C supplementation increases the risk of kidney stones in men, but not in women[45].

Using higher than recommended doses of vitamin C during pregnancy may be harmful to the fetus. High doses of this vitamin, according to the FDA classification of the risk of using drugs during pregnancy, belong to category C. This means that studies in animals have shown adverse effects on the fetus, but its effect on human pregnancy has not been confirmed in clinical trials[46].

Supplementation

Scientific studies on the potential positive health effects of vitamin C supplementation provide conflicting results. A study conducted by the U.S. Preventive Disease Task Force found no evidence of a protective effect of vitamin C supplementation against the development of cardiovascular diseases and cancers[47]. It has also not been clinically proven that vitamin C affects life expectancy[48].

Preventing Cancer Development

A 2013 study did not show that vitamin C supplementation reduces the risk of developing lung cancer in healthy patients and those at high risk (smokers and those exposed to asbestos fiber inhalation)[49]. A meta-analysis from 2014 showed a weak relationship between vitamin C supplementation and reduced incidence of lung cancer[50]. Another meta-analysis showed no association between vitamin C and the risk of prostate cancer[47].

In order to estimate the effect of vitamin C supplementation on the incidence of colorectal cancer, two meta-analyses were performed. One study showed a weak relationship between vitamin C consumption and reduced incidence of this disease. The second showed no such relationship[51][52].

A meta-data analysis from 2011 did not confirm that vitamin C prevents the development of breast cancer[53], but another study showed that vitamin C may be associated with increased survival in patients already ill[54].

Cancer Therapy

Vitamin C, administered intravenously in the form of sodium ascorbate, has a cytotoxic effect on tumors and is indicated as a potential anticancer drug. The authors considered the results promising and justifying the continuation of clinical trials[55][56][57].

Cardiovascular Diseases

A meta-analysis from 2013 showed no effect of vitamin C supplementation on reducing the risk of heart attack, stroke, death from cardiovascular disease or death in general[58]. However, another analysis showed the opposite relationship between vitamin C and the risk of stroke[59].

A meta-analysis of 44 clinical trials showed a significant positive effect of supplementation with daily doses of vitamin C above 500 mg on endothelial function. It was shown that this effect was stronger in people with an increased risk of developing cardiovascular diseases[60].

Chronic Diseases

No effect of vitamin C supplementation on the treatment of rheumatoid arthritis has been demonstrated[61].

Studies examining the effect of vitamin C on the development of Alzheimer's disease have reached conflicting results[62][63]. Maintaining a healthy intake of vitamin C in the diet is probably more important than supplementation[64].

A study of the effect of consuming doses of vitamin C exceeding the RDA did not show its significant effect on preventing and inhibiting the development of age-related cataracts[65].

Common Cold

The effect of vitamin C on the treatment of the common cold has been the subject of many scientific studies. It has been shown that it is not effective in preventing or treating the common cold except in special cases (especially in people who exercise intensively in a cold environment)[66][67]. Routine vitamin C supplementation does not reduce the likelihood of contracting or the severity of a cold in the general population, but it may reduce the duration of the disease[66][68][69].

COVID-19

Administering large doses of sodium ascorbate intravenously has a positive effect on the course of COVID-19 in people infected with SARS-CoV-2. A milder course of the disease and improved saturation were noted, the question of the impact on mortality is not clear and requires further analysis[70][71][72].

Application in the Food Industry

Ascorbic acid is an antioxidant and as such is used in the food industry, as are its salts and esters. Symbols used to mark these compounds:

• E300 – ascorbic acid
• E301 – sodium ascorbate
• E302 – calcium ascorbate
• E303 – potassium ascorbate
• E304 – fatty acid esters and ascorbic acid

  E304(i) – ascorbyl palmitate

  E304(ii) – ascorbyl stearate

• E315 – isoascorbic acid (erythorbic).

History

Symptoms of scurvy were first described in accounts of the Crusades. During the great geographical discoveries (15th–16th centuries), it became the main cause of death and disability of sailors on long voyages. It was not until 1753 that Scottish physician James Lind discovered that eating citrus fruit juice prevents and cures the disease[73]. At the beginning of the 20th century, it was discovered that the guinea pig is also susceptible to this disease and can be an animal model for its research. This made it possible to prove that scurvy is indeed caused by an improper diet[74].

Vitamin C was isolated in 1928 by Hungarian biochemist Albert Szent-Györgyi from bovine adrenal cortex and from orange juice and cabbage juice, and then from peppers. He showed that the isolated compound has antiscorbutic properties and named it "hexuronic acid". In 1933, W.N. Haworth and E.L. Hirst determined its structure, and Haworth and independently T. Reichstein and co-workers described the synthesis of both of its enantiomers. In the same year, Szent-Györgyi and Haworth proposed changing the name of the compound to "ascorbic acid" to illustrate its antiscorbutic properties[74]. In 1937, both scientists were awarded the Nobel Prize for their research on vitamin C[74] – Szent-Györgyi received it in the field of physiology or medicine, and Haworth in the field of chemistry.

Notes

1. ↑ Jump to: 1 2 3 4 5 According to data from USDA Food Composition Databases, the vitamin C content is approx.:

   beef liver: 1–2 mg/100 g[26]

   pork liver: 25 mg/100 g[27]

   cod: 3.5 mg/100 g[28]

   trout: 2–3 mg/100 g[28]

   cow's milk: 1.5 mg/100 g[29].

References

1. ↑ Jump to: a b c d e Pharmacopoeia Poland IX, Polish Pharmaceutical Society, Warsaw: Office for Registration of Medicinal Products, Medical Devices and Biocidal Products, 2011, p. 4574, ISBN 978-83-88157-77-6.
2. ↑ Pharmacopoeia Poland VI, Polish Pharmaceutical Society, Warsaw: Office for Registration of Medicinal Products, Medical Devices and Biocidal Products, 2002, p. 1176, ISBN 83-88157-18-3.
3. ↑ Ascorbic acid, [in:] PubChem [online], United States National Library of Medicine, CID: 54670067 (ang.).
4. ↑ Jump to: a b c d e L-Ascorbic acid (No. A5960) – product safety data sheet Sigma-Aldrich (Merck KGaA) for the area of Polish. [accessed 2011-06-22]. (read if the correct version of the safety data sheet is not displayed)
5. ↑ Ascorbic acid (ICSC: 0379) (pol. • ang.) – international chemical safety card (ICSC), International Labour Organization.
6. ↑ Ascorbic acid (No. A5960) (ang.) – product safety data sheet Sigma-Aldrich (Merck KGaA) for the area of the United States. [accessed 2011-06-22]. (read if the correct version of the safety data sheet is not displayed)
7. ↑ Jump to: a b c d e Thematic dictionary. Biology, part 1, Warsaw: PWN Scientific Publishing House, 2011, p. 21, ISBN 978-83-01-16529-1.
8. ↑ Jump to: a b c d Manfred Eggersdorfer et al.: Vitamins. 10. Vitamin C (l-Ascorbic Acid). In: Ullmann’s Encyclopedia of Industrial Chemistry. Veinheim: Wiley-VCH Verlag, 2005, pp. 110–123. DOI: 10.1002/14356007.a27_443. (English)
9. ↑ Piotr Król, Levorotatory Vitamin C - Properties - Does it differ from Dextrorotatory?, Medicover, June 21, 2018 [accessed 2020-03-01].
10. ↑ Damian Parol, Levorotatory vitamin C, June 19, 2016 [accessed 2020-03-01].
11. ↑ Łukasz Sakowski: Will levorotatory vitamin C cure cancer, or how charlatans deceive people (pol.). CrazyNauka, 2016-10-23. [accessed 2018-01-31]. [for

Specifications