VITAMIN A

Vitamin A is derived from the natural food. 
Natural Vitamin A exists in dif ferent forms. 
In animal tissues, vitamin A is present in the form of retinoids. 

CAS:    68-26-8
MF:    C20H30O
MW:    286.45
EINECS:    200-683-7

Synonyms
Vitamin A1 alcohol;Vitamin A1 alcohol, all-trans-;Vitamin A1, all-trans-;vitamina1alcohol;vitamina1alcohol,alltrans;Vitavel A;Vitamin A (all-trans-Retinol);VITAMIN-A-ALCOHOL SOLUTION, IN HEXANE (0 .25 MG/ML), 1X2 ML

However, in plants, the form of vitamin A called carotenoids is contained in the green, orange, and yellow plant tissue. 
Vitamin A compounds such as retinol, reti nal, carotene, and so on from these foods can be converted to vitamin A in the human body. 
Therefore, food is the main source of vitamin A.
As early as 1000 years ago, the Qian Jin Yao Fang written by Sun Simiao in Tang Dynasty recorded that animal liver can cure night blindness. 
This is the early recognition in vitamin A supplementation. 
The traditional Chinese medicine books also recorded that nourishing the liver can improve eyesight. 
A retinol in which all four exocyclic double bonds have E- (trans-) geometry.
Vitamin A, or retinol, is essential for the proper maintenance of the functional and structural integrity of epithelial cells, and it plays a major role in epithelial differentiation.
Bone development and growth in children have also been linked to adequate vitamin A intake. Vitamin A, when reduced to the aldehyde 11-cis-retinal, combines with opsin to produce the visual pigment rhodopsin. 
This pigment is present in the rods of the retina and is partly responsible for the process of dark adaptation.
Retinal, retinol and retinoic acid are the aldehyde, alcohol and acid forms of vitamin A. 
The retinoids exist as many geometric isomers due to the unsaturated bonds in the aliphatic chain. 
Vitamin A is biologically active in a wide range of processes.

Vitamin A is a fat-soluble vitamin that is an essential nutrient. 
The term "vitamin A" encompasses a group of chemically related organic compounds that includes retinol, retinyl esters, and several provitamin (precursor) carotenoids, most notably β-carotene (beta-carotene).
Vitamin A has multiple functions: growth during embryo development, maintaining the immune system, and healthy vision. 
For aiding vision specifically, it combines with the protein opsin to form rhodopsin, the light-absorbing molecule necessary for both low-light (scotopic vision) and color vision.

Vitamin A occurs as two principal forms in foods: A) retinoids, found in animal-sourced foods, either as retinol or bound to a fatty acid to become a retinyl ester, and B) the carotenoids α-carotene (alpha-carotene), β-carotene, γ-carotene (gamma-carotene), and the xanthophyll beta-cryptoxanthin (all of which contain β-ionone rings) that function as provitamin A in herbivore and omnivore animals which possess the enzymes that cleave and convert provitamin carotenoids to retinol.
Some carnivore species lack this enzyme. 
The other carotenoids do not have retinoid activity.

Dietary retinol is absorbed from the digestive tract via passive diffusion. Unlike retinol, β-carotene is taken up by enterocytes by the membrane transporter protein scavenger receptor B1 (SCARB1), which is upregulated in times of vitamin A deficiency (VAD).
Retinol is stored in lipid droplets in the liver. 
A high capacity for long-term storage of retinol means that well-nourished humans can go months on a vitamin A-deficient diet, while maintaining blood levels in the normal range.
Only when the liver stores are nearly depleted will signs and symptoms of deficiency show.
Vitamin A is reversibly converted to retinal, then irreversibly to retinoic acid, which activates hundreds of genes.

Vitamin A is a fat-soluble vitamin, a category that also includes vitamins D, E and K. 
The vitamin encompasses several chemically related naturally occurring compounds or metabolites, i.e., vitamers, that all contain a β-ionone ring.
The primary dietary form is retinol, which may have a fatty acid molecule attached, creating a retinyl ester, when stored in the liver. 
Retinol – the transport and storage form of vitamin A – is interconvertible with retinal, catalyzed to retinal by retinol dehydrogenases and back to retinol by retinaldehyde reductases.

retinal + NADH + H+ ⇌ retinol + NAD+
retinol + NAD+ ⇌ retinal + NADH + H+
Retinal (also known as retinaldehyde) can be irreversibly converted to all-trans-retinoic acid by the action of retinal dehydrogenase

retinal + NAD+ + H2O → retinoic acid + NADH + H+
Retinoic acid is actively transported into the cell nucleus by CRABp2 where it regulates thousands of genes by binding directly to gene targets via retinoic acid receptors.
In addition to retinol, retinal and retinoic acid, there are plant-, fungi- or bacteria-sourced carotenoids which can be metabolized to retinol, and are thus vitamin A vitamers.

There are also what are referred to as 2nd, 3rd and 4th generation retinoids which are not considered vitamin A vitamers because they cannot be converted to retinol, retinal or all-trans-retinoic acid. 
Some are prescription drugs, oral or topical, for various indications. 
Examples are etretinate, acitretin, adapalene, bexarotene, tazarotene and trifarotene.
Vitamin A’s only a semi-myth that eating carrots will help you see in the dark. 
A carrot’s main nutrient, beta-carotene (responsible for this root vegetable’s characteristic orange color), is a precursor to vitamin A and helps your eyes to adjust in dim conditions. 
Vitamin A can’t give you superpowers of night vision or cure your dependence on contact lenses, but eating an adequate amount will support eye health.
Vitamin A also stimulates the production and activity of white blood cells, takes part in remodeling bone, helps maintain healthy endothelial cells (those lining the body’s interior surfaces), and regulates cell growth and division such as needed for reproduction.
The two main forms of vitamin A in the human diet are preformed vitamin A (retinol, retinyl esters), and provitamin A carotenoids such as alpha-carotene and beta-carotene that are converted to retinol. 
Preformed vitamin A comes from animal products, fortified foods, and vitamin supplements. 
Carotenoids are found naturally in plant foods. 
There are other types of carotenoids found in food that are not converted to vitamin A but have health-promoting properties; these include lycopene, lutein, and zeaxanthin.

History    
The vitamin research is the great achievement in the development of life sciences, while human beings only took half a century to discover and understand vitamins. 
However, everything is still very difficult for scientists in the early stage of vitamin discovery. 
From 1913 to 1915, Elmer McCollum and Marguerite Davis indicated that the growth rate was maintained by at least two different kinds of growth factors: one can be separated from eggs or butter, and the other one which multiple neuritis of chicks and pigeons can be extracted by water; thus they were named fat-soluble vitamin A and water-soluble vitamin B.prevented
In 1919, the researchers demonstrated that fat-soluble vitamin A not only sup ported the rate of growth but also prevented eye dryness and night blindness in the process of property study. 
In 1920, Dr. J.C. Drummond named this active lipid as vitamin A.
Vitamin A exists in cod liver oil and prevents the occurrence of eye dryness and night blindness.

Vitamin A Chemical Properties
Melting point: 61-63 °C(lit.)
Boiling point: 368.81°C (rough estimate)
density: 0.9933 (rough estimate)
refractive index: 1.641
Fp: -26 °C
storage temp.: -20°C
solubility: Chloroform (Slightly), Methanol (Slightly)
pka: 14.09±0.10(Predicted)
form: crystalline
color: yellow to orange
PH: 6.5-7.5 (20°C, 100g/L in H2O)
biological source: synthetic
Water Solubility: Practically insoluble inwaterorglycerol; soluble in absolute alcohol,methanol,℃hloroform, ether, fats and oils.
Sensitive: Moisture & Light Sensitive
Merck: 13,10073
BRN: 403040
Specific Activity: ~3100U/mg
Stability: Stable, but light and air sensitive. Incompatible with strong acids, strong oxidizing agents.
Cosmetics Ingredients Functions: SKIN CONDITIONING - MISCELLANEOUS
InChI: 1S/C20H30O/c1-16(8-6-9-17(2)13-15-21)11-12-19-18(3)10-7-14-20(19,4)5/h6,8-9,11-13,21H,7,10,14-15H2,1-5H3/b9-6+,12-11+,16-8+,17-13+
InChIKey: FPIPGXGPPPQFEQ-OVSJKPMPSA-N
LogP: 5.680
CAS DataBase Reference: 68-26-8(CAS DataBase Reference)
EPA Substance Registry System: Vitamin A (68-26-8)
Vitamin A1 (VA1), Molecular formula, C20H30O; MW, 286.45; CAS, 68-26-8. 
Melting point: 62–64 °C. 
Boiling point: 137–138 °C
VA2, Molecular formula, C20H28O; MW, 284.44; Melting point: 17–19 °C.

Uses    
Vitamin A1 (retinal) is produced from (3-carotene, which can be obtained by fermentation of corn, soybean meal, kerosene, thiamin, and oc-ionone. 
vitamin A (Retinol) is the fat-soluble vitamin a which is required for new cell growth and prevention of night blindness. 
There is no appreciable loss by heating or freezing, and it is stable in the absence of air. 
Sources include liver, fortified margarine, egg, and milk. 
Vitamin A palmitate can be found in frozen egg substitute.
retinol is a retinoid considered to be a skin revitalizer. 
Vitamin A is reported to enhance skin radiance and treat conditions associated with chronological aging, such as wrinkles and fine lines, as well as dermatological disorders, including acne, follicular and lesion papules, actinic keratosis, oily skin, and rosacea. 
According to clinical dermatologists, retinol is one of the few substances with a demonstrated ability to reduce and prevent fine lines and wrinkles. 
Vitamin A is able to alter the behavior of aged cells so they act in a more youthful manner. 

Vitamin A is considered necessary for normal epidermal cell growth and differentiation and stimulates the production of new blood vessels in the skin, improving skin tone. 
In addition, retinol has anti-oxidant capacities and protects dermal fibers by counteracting the increased activity of enzymes that degrade collagen and elastin when the skin is exposed to uV rays. 
Retinol can be drying to the skin when used for a prolonged period of time or in concentrations that are too high. 
A weaker retinoid than retinoic acid, retinol converts to retinoic acid once on the skin. 
When compared to retinoic acid, retinol has an increased penetration potential and is less irritating, making Vitamin A an effective ingredient for anti-aging products. 
The anti-aging benefits of topically treating skin with retinol are based on its penetration ability, which allows it to reach the sites in the skin requiring treatment. When used on sensitive skin for a prolonged period of time or in concentrations that are too high, retinol can cause dermatitis.

Clinical Use    
Principal dietary sources of vitamin A are milk fat (cheese and butter) and eggs. 
Since Vitamin A is stored in the liver, inclusion of liver in the diet also provides vitamin A. 
A plant pigment, carotene, is a precursor for vitamin A and is present in highly pigmented vegetables, such as carrots, rutabaga, and red cabbage.
An early sign of hypovitaminosis A is night blindness. 
This condition is related to the role of vitamin A as the prosthetic group of the visual pigment rhodopsin. 
The night blindness may progress to xerophthalmia (dryness and ulceration of the cornea) and blindness. 
Other symptoms of vitamin A deficiency include cessation of growth and skin changes due to hyperkeratosis.
Since vitamin A is a fat-soluble vitamin, any disease that results in fat malabsorption and impaired liver storage brings with it the risk of vitamin A deficiency; these conditions include biliary tract disease, pancreatic disease, sprue, and hepatic cirrhosis. 
One group at great risk are children from low-income families, who are likely to lack fresh vegetables (carotene) and dairy products (vitamin A) in the diet.

Manufacturing Process    
Manufacturing process for Vitamin A includes these steps as follows: Step A: Synthesis of Preparation of ethyl ether of ethynyl-β-ionol;Step B: Coupling Reaction; Step C:Semi-Hydrogenation of Coupling Product;Step D:Hydrolysis of Semi-Hydrogenated Coupling Product. 
Separation of Vitamin A from the product obtained was achieved by acetylating the total reaction product using pyridine-acetic anhydride at room temperature and chromatographing on alumina neutralized with acetic acid.
A fairly clean separation was achieved. 
The Vitamin A acetate fraction was sufficiently pure to become crystallized from pentane at -15°C when seeded with a pure Vitamin A acetate crystal.
When the Vitamin A acetate was converted to the alcohol form of Vitamin A, the final product showed the characteristic infrared and ultraviolet absorption curves for Vitamin A. Similar results were obtained using as co-solvents (with the liquid ammonia) ethylene diamine and ether; pentane; tetrahydrofuran; diethylamine and hexamethylphosphoramide.

Biochem/physiol Actions    
Retinol and its derivatives exhibit anti-aging properties. 
Retinol is used for treating wrinkles and signs of aging. 
However, due to its photo instability and skin irritation potency, it is hardly used in cosmetic formulations. 
Vitamin A is also used as a therapeutic for dermatoses. 
Vitamin A's deficiency leads to xerosis and follicular hyperkeratosis.

Side effects    
Acute hypervitaminosis A results in drowsiness, headache, vomiting, papilledema, and a bulging fontanel in infants. 
The symptoms of chronic toxicity include scaly skin, hair loss, brittle nails, and hepatosplenomegaly. 
Anorexia, irritability, and swelling of the bones have been seen in children. 
Retardation of growth also may occur. 
Liver toxicity has been associated with excessive vitamin A intake. 
Vitamin A is teratogenic in large amounts, and supplements should not be given during a normal pregnancy.