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Encyclopedia > Retinol
Retinol
Identifiers
CAS number [11103-57-4]
PubChem 1071
Properties
Molecular formula C20H30O
Molar mass 286.456 g/mol
Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)

Infobox disclaimer and references

Retinol, the animal form of vitamin A, is a yellow fat-soluble, antioxidant vitamin important in vision and bone growth. It belongs to the family of chemical compounds known as retinoids. Retinol is ingested in a precursor form; animal sources (milk and eggs) contain retinyl esters, whereas plants (carrots, spinach) contain pro-vitamin A carotenoids. Hydrolysis of retinyl esters results in retinol while pro-vitamin A carotenoids can be cleaved to produce retinal. Retinal, also known as retinaldehyde, can be reversibly reduced to produce retinol or it can be irreversibly oxidized to produce retinoic acid. The best described active retinoid metabolites are 11-cis-retinal and the all-trans and 9-cis-isomers of retinoic acid. Image File history File links No higher resolution available. ... CAS registry numbers are unique numerical identifiers for chemical compounds, polymers, biological sequences, mixtures and alloys. ... PubChem is a database of chemical molecules. ... A chemical formula (also called molecular formula) is a concise way of expressing information about the atoms that constitute a particular chemical compound. ... Molar mass is the mass of one mole of a chemical element or chemical compound. ... In chemistry, the standard state of a material is its state at 1 bar (100 kilopascals) and 25 degrees Celsius (298. ... It has been suggested that Retinol be merged into this article or section. ... This article or section is in need of attention from an expert on the subject. ... The visual system is the part of the nervous system which allows organisms to see. ... Grays Anatomy illustration of a human femur. ... The Retinoids are a class of chemical compounds that are related chemically to vitamin A. Retinoids are used in medicine, primarily due to the way they regulate epithelial cell growth. ... A glass of cows milk A goat kid feeding on its mothers milk Milk is the nutrient fluid secreted by the mammary glands of female mammals (including monotremes). ... An egg is an ovum produced by a female animal for reproduction, often prepared as food. ... General formula of a carboxylate ester. ... Divisions Green algae Chlorophyta Charophyta Land plants (embryophytes) Non-vascular plants (bryophytes) Marchantiophyta - liverworts Anthocerotophyta - hornworts Bryophyta - mosses Vascular plants (tracheophytes) †Rhyniophyta - rhyniophytes †Zosterophyllophyta - zosterophylls Lycopodiophyta - clubmosses †Trimerophytophyta - trimerophytes Pteridophyta - ferns and horsetails Seed plants (spermatophytes) †Pteridospermatophyta - seed ferns Pinophyta - conifers Cycadophyta - cycads Ginkgophyta - ginkgo Gnetophyta - gnetae Magnoliophyta - flowering plants... Binomial name Daucus carota L. Percentages are relative to US recommendations for adults. ... Binomial name Spinacia oleracea L. Percentages are relative to US recommendations for adults. ... Carotenoids are organic pigments that are naturally occurring in plants and some other photosynthetic organisms like algae, some types of fungus and some bacteria. ... Retinal, technically called retinene1 or retinaldehyde, is a light-sensitive retinene molecule found in the photoreceptor cells of the retina. ...

Contents

Discovery

In 1913, Elmer McCollum, a biochemist at the University of Wisconsin-Madison, and colleague Marguerite Davis identified a fat-soluble nutrient in butterfat and cod liver oil. Their work confirmed that of Thomas Osborne and Lafayette Mendel, at Yale, which suggested a fat-soluble nutrient in butterfat, also in 1913 [1]. Vitamin A was first synthesized in 1947. Associated with the discovery of Vitamin A, Elmer McCollum was a biochemist at the University of Wisconsin, who in 1913, along with colleague Marguerite Davis identified a fat-soluble nutrient in butterfat and cod liver oil[1]. McCollum and Davis research validated that of Thomas Osborne and Lafayette Mendel, then... Biochemistry is the chemistry of life. ... The University of Wisconsin–Madison (also known as UW–Madison, Madison, Wisconsin, University of Wisconsin, or UW) is a selective public research university located in Madison, Wisconsin. ... Born September 16, 1887. ... Butterfat or milkfat is the fatty portion of milk. ... Capsules of Cod Liver Oil Cod liver oil, as its name suggests, is an oil extracted from cod livers. ... Thomas Osborne, 1st Duke of Leeds (February 20, 1631 - July 26, 1712), English statesman, commonly known also by his earlier title of Earl of Danby, son of Sir Edward Osborne, Bart. ... Yale redirects here. ...


Chemical structure and function

Many different geometric isomers of retinol, retinal and retinoic acid are possible as a result of either a trans or cis configuration of the four double bonds found in the polyene chain. The cis isomers are less stable and can readily convert to the all-trans configuration (as seen in the structure of all-trans-retinol shown here). Nevertheless, some cis isomers are found naturally and carry out essential functions. For example, the 11-cis-retinal isomer is the chromophore of rhodopsin, the vertebrate photoreceptor molecule. Rhodopsin is comprised of the 11-cis-retinal covalently linked via a Schiff base to the opsin protein (either rod opsin or blue, red or green cone opsins). The process of vision relies on the light-induced isomerisation of the chromophore from 11-cis to all-trans resulting in a change of the conformation and activation of the photoreceptor molecule. One of the earliest signs of vitamin A deficiency is night-blindness followed by decreased visual acuity. Trans is a Latin word meaning across, beyond or on the opposite side and is the opposite of cis, which means on the same side. In chemistry, a bond not subject to free rotation in which the greater radical on both ends is on the opposite side of the bond... CIS usually refers to: Commonwealth of Independent States, a modern-day political entity consisting of 11 former Soviet Union Republics CIS is also an acronym for: Canadian Interuniversity Sport Cancer Information Service Carcinoma in situ Centre for Independent Studies Center for Immigration Studies Chinese International School Cisalpino Citizenship & Immigration Services... Covalent bonding is a form of chemical bonding characterized by the sharing of one or more pairs of electrons between atoms, in order to produce a mutual attraction, which holds the resultant molecule together. ... Polyenes are poly-unsaturated organic compounds that contain one or more sequences of alternating double and single carbon-carbon bonds. ... A chromophore is part (or moiety) of a molecule responsible for its color. ... A rhodopsin molecule (yellow) with bound retinal (orange), embedded in a cell membrane (lipids shown as green, head groups as red/blue). ... Classes and Clades See below Male and female Superb Fairy-wren Vertebrates are members of the subphylum Vertebrata (within the phylum Chordata), specifically, those chordates with backbones or spinal columns. ... A photoreceptor, or photoreceptor cell, is a specialized type of neuron found in the eyes retina that is capable of phototransduction. ... a mixture of 4,4-diaminodiphenyl ether 1 (1. ... A rhodopsin molecule in the cell membrane. ...


George Wald won the 1967 Nobel Prize in Physiology or Medicine for his work with retina pigments (also called visual pigments), which led to the understanding of the role of vitamin A in vision. George Wald (November 18, 1906–April 12, 1997) was an American scientist who is best known for his work with pigments in the retina. ... 1967 (MCMLXVII) was a common year starting on Sunday of the Gregorian calendar (the link is to a full 1967 calendar). ... List of Nobel Prize laureates in Physiology or Medicine from 1901 to the present day. ... Human eye cross-sectional view. ...


Many of the non-visual functions of vitamin A are mediated by retinoic acid, which regulates gene expression by activating intracellular retinoic acid receptors. The non-visual functions of vitamin A are essential in the immunological function, reproduction and embryonic development of vertebrates as evidenced by the impaired growth, susceptibility to infection and birth defects observed in populations receiving suboptimal vitamin A in their diet. There are three retinoic acid receptors (RAR), RAR-alpha, RAR-beta, and RAR-gamma. ...


Role in embryology

It is also a cause of cell differentiation, and plays a part in the growth and development of embryos. During development there is a concentration gradient of retinoic acid along the anterior-posterior (head-tail) axis. Cells in the embryo respond differently to retinoic acid depending on the amount present. For example, in vertebrates the hindbrain transiently forms eight rhombomers and each rhombomere has a specific pattern of genes being expressed. If retinoic acid is not present the last four rhombomeres do not develop. Instead rhombomeres 1-4 grow to cover the same amount of space as all eight would normally occupy. Retinoic acid has its effects by turning on a differential pattern of Hox genes which encode different homeodomain transcription factors which in turn can turn on cell type specific genes. Deletion of the Hox-1 gene from rhombomere 4 makes the neurons growing in that region behave like neurons from rhombomere 2. The retina is also patterned by retinoic acid, with a concentration gradient that is high on the ventral side of the retina and low on the dorsal side.


Vision

Vitamin A is required in the production of rhodopsin, the visual pigment used in low light levels. This is why eating foods rich in vitamin A is said to allow an individual to see in the dark. A rhodopsin molecule (yellow) with bound retinal (orange), embedded in a cell membrane (lipids shown as green, head groups as red/blue). ... Ommochrome (or visual pigment) refers to several biological pigments that occur in the eyes of crustaceans and insects. ...


Epithelial Cells

Vitamin A is essential for the correct functioning of epithelial cells. In Vitamin A deficiency, mucus-secreting cells are replaced by keratin producing cells, leading to xerosis. In zootomy, epithelium is a tissue composed of a layer of cells. ... Microscopy of keratin filaments inside cells. ... Xerosis is the medical term for dry skin. ...


Glycoprotein synthesis

Glycoprotein synthesis requires adequate Vitamin A status. In severe Vitamin A deficiency, lack of glycoproteins may lead to corneal ulcers or liquefaction. A glycoprotein is a macromolecule composed of a protein and a carbohydrate (an oligosaccharide). ...


Immune System

Vitamin A is essential to maintain intact epithelial tissues as a physical barrier to infection; it is also involved in maintaining a number of immune cell types from both the innate and acquired immune systems. These include the lymphocytes (B-cells, T-cells, and natural killer cells), as well as many myelocytes (neutrophils, macrophages, and myeloid dendritic cells). In zootomy, epithelium is a tissue composed of a layer of cells. ... A lymphocyte is a type of white blood cell involved in the human bodys immune system. ... B cells are lymphocytes that play a large role in the humoral immune response (as opposed to the cell-mediated immune response). ... T cells are a subset of lymphocytes that play a large role in the immune response. ... Natural killer cells (NK) are a type of lymphocyte (a white blood cell) and a component of nonspecific immune defense. ... Neutrophil granulocytes (commonly referred to as neutrophils) are a class of white blood cells and are part of the immune system. ... Macrophages (Greek: big eaters) are cells found in tissues that are responsible for phagocytosis of pathogens, dead cells and cellular debris. ... Dendritic cells (DC) are immune cells and form part of the mammal immune system. ...


Formation of red blood cells (Haematopoiesis)

Vitamin A may be needed for normal haematopoiesis; deficiency causes abnormalities in iron metabolism. Diagram that shows the development of different blood cells from hematopoietic stem cell to mature cells Haematopoiesis (from Ancient Greek: haima blood; poiesis to make) (or Hematopoiesis in the United States) is the formation of blood cellular components. ... Human beings use 20 mg of iron each day for the production of new red blood cells, much of which is recycled from old red blood cells. ...


Growth

Vitamin A affects the production of human growth hormone. Growth hormone (GH or somatotropin) is a 191-amino acid, single chain polypeptide hormone which is synthesised, stored and secreted by the somatotroph cells within the lateral wings of the anterior pituitary gland, which stimulates growth and cell reproduction in humans and other animals. ...


Clinical use

Main article: Tretinoin

All retinoid forms of vitamin A are used in cosmetic and medical applications applied to the skin. Retinoic acid, termed Tretinoin in clinical usage, is used in the treatment of acne and keratosis pilaris in a topical cream. An isomer of tretinoin, isotretinoin is is also used orally (under the trade names Accutane and Roaccutane), generally for severe or recalcitrant acne. Tretinoin is the acid form of vitamin A and so also known as all-trans retinoic acid or ATRA. It is a drug commonly used to treat acne vulgaris and keratosis pilaris. ... Tretinoin is the acid form of vitamin A and so also known as all-trans retinoic acid or ATRA. It is a drug commonly used to treat acne vulgaris and keratosis pilaris. ... Keratosis pilaris (KP) is a very common genetic follicular condition that is manifested by the appearance of rough bumps on the skin and hence colloqually referred to as chicken skin. Primarily, it appears on the back and outer sides of the upper arms, but can also occur on thighs and... Isotretinoin (INN) (IPA: ) is a medication used for the treatment of severe acne. ... Isotretinoin is a drug used for the treatment of acne. ...


In cosmetics, vitamin A derivatives are used as so-called antiaging chemicals- vitamin A is absorbed through the skin and increases the rate of skin turnover, and gives a temporary increase in collagen giving a more youthful appearance. Tropocollagen triple helix. ...


Tretinoin, under the alternative name of all-trans retinoic acid (ATRA), is used as chemotherapy for acute promyelocytic leukemia, a subtype of acute myelogenous leukemia. This is because cells of this subtype of leukemia are sensitive to agonists of the retinoic acid receptors (RARs). Acute myelogenous leukemia (AML), also known as acute myeloid leukemia, is a cancer of the myeloid line of white blood cells. ... Acute myelogenous leukemia (AML), also known as acute myeloid leukemia, is a cancer of the myeloid line of blood cells. ...


Units of measurement

When referring to dietary allowances or nutritional science, retinol is usually measured in international units (IU). IU refers to biological activity and therefore is unique to each individual compound, however 1 IU of retinol is equivalent to approximately 0.3 micrograms (300 nanograms). The updated USDA food pyramid, published in 2005, is a general nutrition guide for recommended food consumption. ... In pharmacology, the International unit (IU, alternatively abbreviated UI, from French unité internationale) is a unit of measurement for the amount of a substance, based on measured biological activity (or effect). ...


Nutrition

Vitamin properties
Solubility Fat
RDA (adult male) 900 µg/day
RDA (adult female) 700 µg/day
RDA upper limit (adult male) 3,000 µg/day
RDA upper limit (adult female) 3,000 µg/day
Deficiency symptoms
Excess symptoms
Common sources

This vitamin plays an essential role in vision, particularly night vision, normal bone and tooth development, reproduction, and the health of skin and mucous membranes (the mucus-secreting layer that lines body regions such as the respiratory tract). Vitamin A also acts in the body as an antioxidant, a protective chemical that may reduce the risk of certain cancers. Solubility refers to the ability for a given substance, the solute, to dissolve in a solvent. ... It has been suggested that this article or section be merged with Daily values. ... The microgram (symbol µg, sometimes mcg) is an SI unit of mass. ... The microgram (symbol µg, sometimes mcg) is an SI unit of mass. ... The microgram (symbol µg, sometimes mcg) is an SI unit of mass. ... The microgram (symbol µg, sometimes mcg) is an SI unit of mass. ... Nyctalopia (literally night blindness) is a condition making it difficult or impossible to see in the dark. ... Keratomalacia is a eye disorder that leads to a dry cornea. ... // Teratogenesis is a medical term from the Greek, literally meaning monster-birth, which derives from teratology, the study of the frequency, causation, and development of congenital malformations—misleadingly called birth defects. ... Osteoporosis is a disease of bone in which the bone mineral density (BMD) is reduced, bone microarchitecture is disrupted, and the amount and variety of non-collagenous proteins in bone is altered. ... The liver is an organ in some animals, including vertebrates (and therefore humans). ... Dairy products are generally defined as foodstuffs produced from milk. ... For other uses, see Fruit (disambiguation). ... Chinese cabbage Swiss chard Leaf vegetables, also called greens or leafy greens, are plant leaves eaten as a vegetable, sometimes accompanied by tender petioles and shoots. ...


There are two sources of dietary vitamin A. Active forms, which are immediately available to the body are obtained from animal products. These are known as retinoids and include retinal and retinol. Precursors, also known as provitamins, which must be converted to active forms by the body, are obtained from fruits and vegetables containing yellow, orange and dark green pigments, known as carotenoids, the most well-known being beta-carotene. For this reason, amounts of vitamin A are measured in Retinal Equivalents (RE). One RE is equivalent to 0.001mg of retinal, or 0.006mg of beta-carotene, or 3.3 International Units of vitamin A.


In the intestine, vitamin A is protected from being chemically changed by vitamin E. Vitamin A is fat-soluble and can be stored in the body. Most of the vitamin A you eat is stored in the liver. When required by a particular part of the body, the liver releases some vitamin A, which is carried by the blood and delivered to the target cells and tissues.


Dietary intake

The Dietary Reference Intake (DRI) Recommended Daily Amount (RDA) for Vitamin A for a 25-year old male is 900 micrograms/day, or 3,000 IU. Dietary Reference Intake is a set of guidelines set up in 1997 to give more detailed guidance than the RDA system which preceded it. ...


The Food Standards Agency states that an average adult should not consume more than 1.5 milligrammes per day, because this increases the chance of osteoporosis. The Food Standards Agency is a non-ministerial government department of the Government of the United Kingdom. ... Osteoporosis is a disease of bone in which the bone mineral density (BMD) is reduced, bone microarchitecture is disrupted, and the amount and variety of non-collagenous proteins in bone is altered. ...


During the absorption process in the intestines, retinol is incorporated into chylomicrons as the ester form, and it is these particles that mediate transport to the liver. Liver cells (hepatocytes) store vitamin A as the ester, and when retinol is needed in other tissues, it is de-esterifed and released into the blood as the alcohol. Retinol then attaches to a serum carrier, retinol binding protein, for transport to target tissues. A binding protein inside cells, cellular retinoic acid binding protein, serves to store and move retinoic acid intracellularly. Carotenoid bioavailability ranges between 1/5 to 1/10 of retinol's. Carotenoids are better absorbed when ingested as part of a fatty meal. Also, the carotenoids in vegetables, especially those with tough cell walls (e.g. carrots), are better absorbed when these cell walls are broken up by cooking or mincing. In anatomy, the intestine is the portion of the alimentary canal extending from the stomach to the anus and, in humans and other mammals, consists of two segments, the small intestine and the large intestine (or colon). ... Chylomicrons are large lipoprotein particles (having a diameter of 75 to 1,200nm) that are created by the absorptive cells of the small intestine. ... The liver is an organ in some animals, including vertebrates (and therefore humans). ... Hepatocytes make up 60-80% of the cytoplasmic mass of the liver. ... Retinol, the dietary form of vitamin A, is a fat-soluble, antioxidant vitamin important in vision and bone growth. ... In cell biology, molecular biology and related fields, the word intracellular means inside the cell. It is used in contrast to extracellular (outside the cell). ... In pharmacology, bioavailability is used to describe the fraction of an administered dose of medication that reaches the systemic circulation, one of the principal pharmacokinetic properties of drugs. ...


Vitamin A deficiency

see Vitamin A deficiency for details
Prevalence of vitamin A deficiency. Source: WHO
Prevalence of vitamin A deficiency. Source: WHO

Vitamin A deficiency is common in developing countries but rarely seen in developed countries. Approximately 250,000 to 500,000 malnourished children in the developing world go blind each year from a deficiency of vitamin A. Night blindness is one of the first signs of vitamin A deficiency. Vitamin A deficiency contributes to blindness by making the cornea very dry and damaging the retina and cornea. Image File history File links Download high resolution version (1357x628, 51 KB)Prevalance of Vitamin A deficiency, from WHO data [1] Made by User:Petaholmes File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Image File history File links Download high resolution version (1357x628, 51 KB)Prevalance of Vitamin A deficiency, from WHO data [1] Made by User:Petaholmes File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... The World Health Organization (WHO) is a specialized agency of the United Nations that acts as a coordinating authority on international public health, headquartered in Geneva, Switzerland. ... Nyctalopia (literally night blindness) is a condition making it difficult or impossible to see in the dark. ... The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber, providing most of an eyes optical power [1]. Together with the lens, the cornea refracts light and, as a result, helps the eye to focus. ... Human eye cross-sectional view. ...


Vitamin A overdose (Toxicity)

see Hypervitaminosis A for details

The Tolerable Upper Intake Level (UL) for vitamin A, for a 25-year old male, is 3,000 micrograms/day, or about 10,000 IU. The effects of excessive vitamin A intake include: birth defects liver abnormalities, reduced bone mineral density that may result in osteoporosis coarse bone growths hair loss excessive skin dryness/peeling Signs of acute toxicity include nausea and vomiting, headache, dizziness, blurred vision, and loss of muscular coordination. ... Dietary Reference Intake is a set of guidelines set up in 1997 to give more detailed guidance than the RDA system which preceded it. ...


Too much vitamin A can be harmful or fatal, resulting in what is known as hypervitaminosis A. The body converts the dimerized form, carotene, into vitamin A as it is needed, therefore high levels of carotene are not toxic compared to the ester (animal) forms. The livers of certain animals, especially those adapted to polar environments, often contain amounts of vitamin A that would be toxic to humans. Thus, vitamin A toxicity is typically reported in arctic explorers and people taking large doses of synthetic vitamin A. The first documented death due to vitamin A poisoning was Xavier Mertz, a Swiss scientist who died in January 1913 on an Antarctic expedition that had lost its food supplies and fell to eating its sled dogs [citation needed]. Mertz consumed lethal amounts of vitamin A by eating the dogs' livers. Just 0.3 grams of the liver of the polar bear contains the upper intake level.[2]. If eaten in one meal, 30 to 90 grams is enough to kill a human being, or to make even sled dogs very ill. Carotene is responsible for the orange colour of the carrots and many other fruits and vegetables. ... Xavier Mertz (1883–1912) was a Swiss explorer, principally famous for his adventures in the Antarctic. ... For other uses, see Antarctica (disambiguation). ... Binomial name Ursus maritimus Phipps, 1774 The polar bear (Ursus maritimus), also known as the white bear, northern bear, or sea bear, is an Arctic native and the apex predator within its range. ...


Excess vitamin A has also been suspected to be a contributor to osteoporosis. This seems to happen at much lower doses than those required to induce acute intoxication. Only preformed vitamin A can cause these problems, because the conversion of carotenoids into vitamin A is downregulated when physiological requirements are met. An excessive uptake of carotenoids can, however, cause carotenosis. Osteoporosis is a disease of bone in which the bone mineral density (BMD) is reduced, bone microarchitecture is disrupted, and the amount and variety of non-collagenous proteins in bone is altered. ... Carotenosis, or carotenosis cutis, is a benign yellowing of the skin in humans caused by high dietary uptake of carotenoids. ...


The carotenoid beta carotene was interestingly associated with an increase in lung cancer when it was studied in a lung cancer prevention trial in male smokers. In non-smokers, the opposite effect has been noted. Carotene is a terpene, an orange photosynthetic pigment, important for photosynthesis. ... Lung cancer is the malignant transformation and expansion of lung tissue, and is the most lethal of all cancers worldwide, responsible for up to 3 million deaths annually. ...


Excess preformed vitamin A during early pregnancy has also been associated with a significant increase in birth defects.[2] These defects may be severe, even life-threatening. Even twice the daily recommended amount can cause severe birth defects.[3] The FDA currently recommends that pregnant women get their Vitamin A from foods containing beta carotene and that they should ensure that they consume no more than 5,000 IU of preformed Vitamin A (if any) per day. Although Vitamin A is necessary for fetal development, most women carry stores of Vitamin A in their fat cells, so oversupplementation should be strictly avoided.


A review of all randomized controlled trials in the scientific literature by the Cochrane Collaboration published in JAMA in 2007 found that vitamin A significantly increased mortality by 16% (Relative Risk 1.16, 95% confidence interval 1.10-1.24).[3] The Cochrane Collaboration developed in response to Archie Cochranes call for systematic, up-to-date reviews (currently known as systematic reviews) of all relevant randomized clinical trials of health care. ... JAMA, published continuously since in 1883, is an international peer-reviewed general medical journal published 48 times per year. ...


Good sources

Vitamin A is found naturally in many foods. Each of the following contains at least 0.15mg of Vitamin A or beta carotene per 1.75-7 oz. (50-200g):

Binomial name Ipomoea batatas Linnaeus, The sweet potato (Ipomoea batatas) is a crop plant whose large, starchy, sweet-tasting tuberous roots are an important root vegetable. ... Binomial name Daucus carota A carrot (Daucus Carota) is a root vegetable, typically orange or white in color with a woody texture. ... Collards, also called collard greens or borekale (Brassica oleracea Acephala Group), are various loose-leafed cultivars of the cabbage plant. ... Kale (also called Borecole) is a form of cabbage (Brassica oleracea Acephala Group), green in color, in which the central leaves do not form a head. ... For the film, see Pumpkin (film). ... Binomial name Spinacia oleracea L. Percentages are relative to US recommendations for adults. ... Species C. annuum (incl. ... Winter squash is a warm-seasoned vegetable. ... Binomial name Prunus armeniaca The scientific name for the apricot is Prunus armeniaca L., which puts it in the same subgenus as the plum (Prunophora). ... Trinomial name Cucumis melo cantalupensis Cucumis melo reticulatus Naudin. ... Species About 35 species, including: Mangifera altissima Mangifera applanata Mangifera caesia Mangifera camptosperma Mangifera casturi Mangifera decandra Mangifera foetida Mangifera gedebe Mangifera griffithii Mangifera indica Mangifera kemanga Mangifera laurina Mangifera longipes Mangifera macrocarpa Mangifera mekongensis Mangifera odorata Mangifera pajang Mangifera pentandra Mangifera persiciformis Mangifera quadrifida Mangifera siamensis Mangifera similis Mangifera... The liver is an organ in some animals, including vertebrates (and therefore humans). ... An egg is an ovum produced by a female animal for reproduction, often prepared as food. ... Broccoli is a plant of the Cabbage family, Brassicaceae (formerly Cruciferae). ...

Synthetic Sources

Synthetic retinol is marketed under the following trade names: Acon, Afaxin, Agiolan, Alphalin, Anatola, Aoral, Apexol, Apostavit, Atav, Avibon, Avita, Avitol, Axerol, Dohyfral A, Epiteliol, Nio-A-Let, Prepalin, Testavol, Vaflol, Vi-Alpha, Vitpex, Vogan, and Vogan-Neu. In chemistry, chemical synthesis is purposeful execution of chemical reactions in order to get a product, or several products. ...


Night vision

Night blindness - the inability to see well in dim light - is associated with a deficiency of vitamin A. This vitamin is needed for the formation of rhodopsin. This is a pigment located in the eye's retina, which is the light-sensitive tissue lining in the back of the eye. A rhodopsin molecule (yellow) with bound retinal (orange), embedded in a cell membrane (lipids shown as green, head groups as red/blue). ...


When stimulated by light, rhodopsin splits into a protein and a cofactor: opsin and retinal (a form of vitamin A); when it is dark the reverse reaction occurs - the retinal and opsin combine to re-form rhodopsin, a reaction that requires extra retinal.


Without adequate amounts of retinal, regeneration of rhodopsin is incomplete and night blindness occurs. Since carrots are a good source of beta-carotene, there is truth in the old belief that carrots help you see better in the dark.


Closely related chemicals

  • Tretinoin (Tradename: Retin-A)
  • Isotretinoin (Tradename: Accutane(US), Roaccutane)
  • Retinyl palmitate ("vitamin A" or "pro-vitamin A")

Tretinoin is the acid form of vitamin A and so also known as all-trans retinoic acid or ATRA. It is a drug commonly used to treat acne vulgaris and keratosis pilaris. ... Isotretinoin (INN) (IPA: ) is a medication used for the treatment of severe acne. ...

Genetically engineered vitamin A enriched rice

Due to the high prevalence of vitamin A deficiency in developing countries, there are efforts to produce genetically modified rice rich in beta carotene. The idea is that this would help poor people, who can't afford a varied diet containing sufficient natural sources of vitamin A, meet their dietary needs. The golden rice project is one such effort, and is already undergoing trials.  High human development Medium human development Low human development Unavailable A developing country has a relatively low standard of living, an undeveloped industrial base, and a moderate to low Human Development Index (HDI) score. ... Genetic engineering, genetic modification (GM), and gene splicing (once in widespread use but now deprecated) are terms for the process of manipulating genes in an organism, usually outside of the organisms normal reproductive process. ... White rice and golden rice Golden rice is a variety of rice (Oryza sativa) produced through genetic engineering to biosynthesize the precursors of beta-carotene (pro-vitamin A) in the edible parts of rice. ...


References

  1. ^ Semba RD. Vitamin A as "Anti-Infective" Therapy, 1920–1940. Journal of Nutrition. 1999;129:783-791. PMID 10203551. Full Text Available
  2. ^ A. Aggrawal, Death by Vitamin A
  3. ^ Bjelakovic et al., Mortality in randomized trials of antioxidant supplements for primary and secondary prevention: Systematic review and meta-analysis, JAMA, 297:842; Feb. 28, 2007 [1]

External links

  • Links to external chemical sources

  Results from FactBites:
 
Vitamin A (Retinol) - MayoClinic.com (4145 words)
In preliminary study, retinol palmitate significantly reduced rectal symptoms of radiation proctopathy, perhaps because of wound-healing effects.
As retinol activity equivalents (RAEs), 1 RAE = 1 mcg retinal, 12 mcg beta-carotene, 24 mcg alpha-carotene, or 24 mcg beta cryptoxanthin in foods.
Ehrenpreis, E. D., Jani, A., Levitsky, J., Ahn, J., and Hong, J. A prospective, randomized, double-blind, placebo-controlled trial of retinol palmitate (vitamin A) for symptomatic chronic radiation proctopathy.
Retinol (2350 words)
One RE of vitamin A is equal to 3.33 Units of retinol and 10 Units of beta-carotene.
Breast-feeding females—1200 to 1300 RE (4000 to 4330 Units of retinol or 6000 to 6500 Units as a combination of retinol and beta-carotene) per day.
Children birth to 3 years of age—375 to 400 RE (1250 to 1330 Units of retinol or 1875 to 2000 Units as a combination of retinol and beta-carotene) per day.
  More results at FactBites »

 
 

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