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Vitamin A2
Vitamin A2 is a subcategory of vitamin A, including vitamin A1 in the form of retinol, retinyl esters, retinal, and provitamin A carotenoids. Dehydroretinal (3,4-dehydroretinal) belongs to the group of vitamin A2 as a retinaldehyde form, besides the endogenous 3,4-dehydroretinol (vitamin A2 alcohol), and 3,4-dehydroretinoic acid (vitamin A2 acid). Vitamin A2 was first identified by Richard Alan Morton using newly-developed absorption spectroscopy Absorption spectroscopy refers to spectroscopic techniques that measure the absorption of radiation, as a function of frequency or wavelength, due to its interaction with a sample. The sample absorbs energy, i.e., photons, from the radiating fie ... in 1941. References {{Reflist Vitamins Carotenoids ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vitamin A
Vitamin A is a fat-soluble vitamin and an essential nutrient for humans. It is a group of organic compounds that includes retinol, retinal (also known as retinaldehyde), retinoic acid, and several provitamin A carotenoids (most notably beta-carotene ˛-carotene. Vitamin A has multiple functions: it is essential for embryo development and growth, for maintenance of the immune system, and for vision, where 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) retinol, found in animal-sourced foods, either as retinol or bound to a fatty acid to become a retinyl ester, and B) the carotenoids alpha-carotene, β-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 provi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Retinol
Retinol, also called vitamin A1, is a fat-soluble vitamin in the vitamin A family found in food and used as a dietary supplement. As a supplement it is used to treat and prevent vitamin A deficiency, especially that which results in xerophthalmia. In regions where deficiency is common, a single large dose is recommended to those at high risk twice a year. It is also used to reduce the risk of complications in measles patients. It is taken by mouth or by injection into a muscle. Retinol at normal doses is well tolerated. High doses may cause enlargement of the liver, dry skin, and hypervitaminosis A. High doses during pregnancy may harm the fetus. The body converts retinol to retinal and retinoic acid, through which it acts. Dietary sources include fish, dairy products, and meat. Retinol was discovered in 1909, isolated in 1931, and first made in 1947. It is on the World Health Organization's List of Essential Medicines. Retinol is available as a generic medication and over ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Retinal
Retinal (also known as retinaldehyde) is a polyene chromophore. Retinal, bound to proteins called opsins, is the chemical basis of visual phototransduction, the light-detection stage of visual perception (vision). Some microorganisms use retinal to convert light into metabolic energy. In fact, a recent study suggests most living organisms on our planet ~3 billion years ago used retinal to convert sunlight into energy rather than chlorophyll. Since retinal absorbs mostly green light and transmits purple light, this gave rise to the Purple Earth Hypothesis. There are many forms of vitamin A — all of which are converted to retinal, which cannot be made without them. Retinal itself is considered to be a form of vitamin A when eaten by an animal. The number of different molecules that can be converted to retinal varies from species to species. Retinal was originally called retinene, and was renamed after it was discovered to be vitamin A aldehyde. Vertebrate animals ingest reti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Provitamin A
A provitamin is a substance that may be converted within the body to a vitamin. The term previtamin is a synonym. The term "provitamin" is used when it is desirable to label a substance with little or no vitamin activity, but which can be converted to an active form by normal metabolic processes. Some provitamins are: * "Provitamin A" is a name for β-carotene, which has only about 1/6 the biological activity of retinol (vitamin A); the body uses an enzyme to convert β-carotene to retinol. In other contexts, both β-carotene and retinol are simply considered to be different forms (vitamers) of vitamin A. * "Provitamin B5" is a name for panthenol, which may be converted in the body to vitamin B5 (pantothenic acid). * Menadione is a synthetic provitamin of vitamin K. * Provitamin D2 is ergosterol Ergosterol (ergosta-5,7,22-trien-3β-ol) is a sterol found in cell membranes of fungi and protozoa, serving many of the same functions that cholesterol serves in animal cells. Because many ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carotenoid
Carotenoids (), also called tetraterpenoids, are yellow, orange, and red organic compound, organic pigments that are produced by plants and algae, as well as several bacteria, and Fungus, fungi. Carotenoids give the characteristic color to pumpkins, carrots, parsnips, maize, corn, tomatoes, Domestic Canary, canaries, flamingos, salmon, lobster, shrimp, and daffodils. Carotenoids can be produced from Lipid, fats and other basic organic metabolic building blocks by all these organisms. It is also produced by Endosymbiont, endosymbiotic bacteria in Whitefly, whiteflies. Carotenoids from the diet are stored in the fatty tissues of animals, and exclusively Carnivore, carnivorous animals obtain the compounds from animal fat. In the human diet, Small intestine#Absorption, absorption of carotenoids is improved when consumed with fat in a meal. Cooking carotenoid-containing vegetables in oil and shredding the vegetable both increase carotenoid bioavailability. There are over 1,100 known c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dehydroretinal
Dehydroretinal (3,4-dehydroretinal) is a derivative metabolite of retinal belonging to the group of vitamin A2 as a retinaldehyde form, besides the endogenously present 3,4-dehydroretinol and 3,4-dehydroretinoic acid. The livers of some freshwater fishes and some fish found in India contain a higher ratio of dehydroretinal to retinal than do other species. See also * Retinene The retinenes (retinene1 and retinene2) are chemical derivatives of vitamin A (see retinol) formed through oxidation reactions. Retinene1 is better known as retinal and is fundamental in the transduction of light into visual signals in the photo ... References {{Reflist Vision Signal transduction Apocarotenoids Photosynthetic pigments Vitamins ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Absorption Spectroscopy
Absorption spectroscopy refers to spectroscopic techniques that measure the absorption of radiation, as a function of frequency or wavelength, due to its interaction with a sample. The sample absorbs energy, i.e., photons, from the radiating field. The intensity of the absorption varies as a function of frequency, and this variation is the absorption spectrum. Absorption spectroscopy is performed across the electromagnetic spectrum. Absorption spectroscopy is employed as an analytical chemistry tool to determine the presence of a particular substance in a sample and, in many cases, to quantify the amount of the substance present. Infrared and ultraviolet–visible spectroscopy are particularly common in analytical applications. Absorption spectroscopy is also employed in studies of molecular and atomic physics, astronomical spectroscopy and remote sensing. There is a wide range of experimental approaches for measuring absorption spectra. The most common arrangement is to direct ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vitamins
A vitamin is an organic molecule (or a set of molecules closely related chemically, i.e. vitamers) that is an essential micronutrient that an organism needs in small quantities for the proper functioning of its metabolism. Essential nutrients cannot be synthesized in the organism, either at all or not in sufficient quantities, and therefore must be obtained through the diet. Vitamin C can be synthesized by some species but not by others; it is not a vitamin in the first instance but is in the second. The term ''vitamin'' does not include the three other groups of essential nutrients: minerals, essential fatty acids, and essential amino acids. Most vitamins are not single molecules, but groups of related molecules called vitamers. For example, there are eight vitamers of vitamin E: four tocopherols and four tocotrienols. Some sources list fourteen vitamins, by including choline, but major health organizations list thirteen: vitamin A (as all-''trans''-retinol, all-''trans''- ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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