Carotenoid
Overview
 
Carotenoids are tetraterpenoid
Tetraterpenoid
Tetraterpenoids are terpenoids of 8 isoprene units - hence 40 carbon atoms in the skeleton.Notable subgroups are*carotenoidsOthers*trianthenol 1*methyl tortuoate C from coral...

 organic
Organic compound
An organic compound is any member of a large class of gaseous, liquid, or solid chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of carbon-containing compounds such as carbides, carbonates, simple oxides of carbon, and cyanides, as well as the...

 pigment
Pigment
A pigment is a material that changes the color of reflected or transmitted light as the result of wavelength-selective absorption. This physical process differs from fluorescence, phosphorescence, and other forms of luminescence, in which a material emits light.Many materials selectively absorb...

s that are naturally occurring in the chloroplast
Chloroplast
Chloroplasts are organelles found in plant cells and other eukaryotic organisms that conduct photosynthesis. Chloroplasts capture light energy to conserve free energy in the form of ATP and reduce NADP to NADPH through a complex set of processes called photosynthesis.Chloroplasts are green...

s and chromoplast
Chromoplast
Chromoplasts are plastids responsible for pigment synthesis and storage. They, like all other plastids , are organelles found in specific photosynthetic eukaryotic species....

s of plants and some other photosynthetic
Photosynthesis
Photosynthesis is a chemical process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs, since they can...

 organism
Organism
In biology, an organism is any contiguous living system . In at least some form, all organisms are capable of response to stimuli, reproduction, growth and development, and maintenance of homoeostasis as a stable whole.An organism may either be unicellular or, as in the case of humans, comprise...

s like algae
Algae
Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms, such as the giant kelps that grow to 65 meters in length. They are photosynthetic like plants, and "simple" because their tissues are not organized into the many...

, some bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

, and some types of fungus
Fungus
A fungus is a member of a large group of eukaryotic organisms that includes microorganisms such as yeasts and molds , as well as the more familiar mushrooms. These organisms are classified as a kingdom, Fungi, which is separate from plants, animals, and bacteria...

. Carotenoids can be synthesized fats and other basic organic metabolic building blocks by all these organisms. Carotenoids generally cannot be manufactured by species in the animal kingdom (although one species of aphid is known to have acquired the genes
Gênes
Gênes is the name of a département of the First French Empire in present Italy, named after the city of Genoa. It was formed in 1805, when Napoleon Bonaparte occupied the Republic of Genoa. Its capital was Genoa, and it was divided in the arrondissements of Genoa, Bobbio, Novi Ligure, Tortona and...

 for synthesis of the carotenoid torulene
Torulene
Torulene is a carotene which is notable for being synthesized by red pea aphids , imparting the natural red color to the aphids, which aids in their camouflage and escape from predation...

 from fungi by horizontal gene transfer
Horizontal gene transfer
Horizontal gene transfer , also lateral gene transfer , is any process in which an organism incorporates genetic material from another organism without being the offspring of that organism...

).
Encyclopedia
Carotenoids are tetraterpenoid
Tetraterpenoid
Tetraterpenoids are terpenoids of 8 isoprene units - hence 40 carbon atoms in the skeleton.Notable subgroups are*carotenoidsOthers*trianthenol 1*methyl tortuoate C from coral...

 organic
Organic compound
An organic compound is any member of a large class of gaseous, liquid, or solid chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of carbon-containing compounds such as carbides, carbonates, simple oxides of carbon, and cyanides, as well as the...

 pigment
Pigment
A pigment is a material that changes the color of reflected or transmitted light as the result of wavelength-selective absorption. This physical process differs from fluorescence, phosphorescence, and other forms of luminescence, in which a material emits light.Many materials selectively absorb...

s that are naturally occurring in the chloroplast
Chloroplast
Chloroplasts are organelles found in plant cells and other eukaryotic organisms that conduct photosynthesis. Chloroplasts capture light energy to conserve free energy in the form of ATP and reduce NADP to NADPH through a complex set of processes called photosynthesis.Chloroplasts are green...

s and chromoplast
Chromoplast
Chromoplasts are plastids responsible for pigment synthesis and storage. They, like all other plastids , are organelles found in specific photosynthetic eukaryotic species....

s of plants and some other photosynthetic
Photosynthesis
Photosynthesis is a chemical process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs, since they can...

 organism
Organism
In biology, an organism is any contiguous living system . In at least some form, all organisms are capable of response to stimuli, reproduction, growth and development, and maintenance of homoeostasis as a stable whole.An organism may either be unicellular or, as in the case of humans, comprise...

s like algae
Algae
Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms, such as the giant kelps that grow to 65 meters in length. They are photosynthetic like plants, and "simple" because their tissues are not organized into the many...

, some bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

, and some types of fungus
Fungus
A fungus is a member of a large group of eukaryotic organisms that includes microorganisms such as yeasts and molds , as well as the more familiar mushrooms. These organisms are classified as a kingdom, Fungi, which is separate from plants, animals, and bacteria...

. Carotenoids can be synthesized fats and other basic organic metabolic building blocks by all these organisms. Carotenoids generally cannot be manufactured by species in the animal kingdom (although one species of aphid is known to have acquired the genes
Gênes
Gênes is the name of a département of the First French Empire in present Italy, named after the city of Genoa. It was formed in 1805, when Napoleon Bonaparte occupied the Republic of Genoa. Its capital was Genoa, and it was divided in the arrondissements of Genoa, Bobbio, Novi Ligure, Tortona and...

 for synthesis of the carotenoid torulene
Torulene
Torulene is a carotene which is notable for being synthesized by red pea aphids , imparting the natural red color to the aphids, which aids in their camouflage and escape from predation...

 from fungi by horizontal gene transfer
Horizontal gene transfer
Horizontal gene transfer , also lateral gene transfer , is any process in which an organism incorporates genetic material from another organism without being the offspring of that organism...

). Animals obtain carotenoids in their diets, and may employ them in various ways in metabolism.

There are over 600 known carotenoids; they are split into two classes, xanthophyll
Xanthophyll
Xanthophylls are yellow pigments that form one of two major divisions of the carotenoid group. The name is from Greek xanthos + phyllon , due to their formation of the yellow band seen in early chromatography of leaf pigments...

s (which contain oxygen) and carotene
Carotene
The term carotene is used for several related unsaturated hydrocarbon substances having the formula C40Hx, which are synthesized by plants but cannot be made by animals. Carotene is an orange photosynthetic pigment important for photosynthesis. Carotenes are all coloured to the human eye...

s (which are purely hydrocarbons, and contain no oxygen). Carotenoids in general absorb blue light. They serve two key roles in plants and algae: they absorb light energy for use in photosynthesis, and they protect chlorophyll from photodamage. In humans, four carotenoids (beta-carotene
Beta-carotene
β-Carotene is a strongly-coloured red-orange pigment abundant in plants and fruits. It is an organic compound and chemically is classified as a hydrocarbon and specifically as a terpenoid , reflecting its derivation from isoprene units...

, alpha-carotene
Alpha-carotene
α-Carotene is a form of carotene with a β-ring at one end and an ε-ring at the other. It is the second most common form of carotene.-Human physiology:...

, gamma-carotene, and beta-cryptoxanthin
Cryptoxanthin
Cryptoxanthin is a natural carotenoid pigment. It has been isolated from a variety of sources including the petals and flowers of plants in the genus Physalis, orange rind, papaya, egg yolk, butter, apples, and bovine blood serum.-Chemistry:...

) have vitamin A
Vitamin A
Vitamin A is a vitamin that is needed by the retina of the eye in the form of a specific metabolite, the light-absorbing molecule retinal, that is necessary for both low-light and color vision...

 activity (meaning they can be converted to retinal
Retinal
Retinal, also called retinaldehyde or vitamin A aldehyde, is one of the many forms of vitamin A . Retinal is a polyene chromophore, and bound to proteins called opsins, is the chemical basis of animal vision...

), and these and other carotenoids can also act as antioxidant
Antioxidant
An antioxidant is a molecule capable of inhibiting the oxidation of other molecules. Oxidation is a chemical reaction that transfers electrons or hydrogen from a substance to an oxidizing agent. Oxidation reactions can produce free radicals. In turn, these radicals can start chain reactions. When...

s. In the eye, certain other carotenoids (lutein
Lutein
Lutein is a xanthophyll and one of 600 known naturally occurring carotenoids. Lutein is synthesized only by plants and like other xanthophylls is found in high quantities in green leafy vegetables such as spinach and kale...

 and zeaxanthin
Zeaxanthin
Zeaxanthin is one of the most common carotenoid alcohols found in nature. It is important in the xanthophyll cycle. Synthesized in plants & some micro-organisms, it is the pigment that gives paprika , corn, saffron, and many other plants & microbes their characteristic color.The name is derived...

) apparently act directly to absorb damaging blue and near-ultraviolet light, in order to protect the macula lutea.

People consuming diets rich in carotenoids from natural foods, such as fruits and vegetables, are healthier and have lower mortality from a number of chronic illnesses. However, a recent meta-analysis of 68 reliable antioxidant supplementation experiments involving a total of 232,606 individuals concluded that consuming additional β-carotene from supplements is unlikely to be beneficial and may actually be harmful, although this conclusion may be due to the inclusion of studies involving smokers. With the notable exception of Vietnam Gac
Gac
Momordica cochinchinensis is a Southeast Asian fruit found throughout the region from Southern China to Northeastern Australia.-Etymology:It is commonly known as gac, from the Vietnamese gấc or quả gấc...

 and crude palm oil
Palm oil
Palm oil, coconut oil and palm kernel oil are edible plant oils derived from the fruits of palm trees. Palm oil is extracted from the pulp of the fruit of the oil palm Elaeis guineensis; palm kernel oil is derived from the kernel of the oil palm and coconut oil is derived from the kernel of the...

, most carotenoid-rich fruits and vegetables are low in lipids. Since dietary lipids have been hypothesized to be an important factor for carotenoid bioavailability, a 2005 study investigated whether addition of avocado fruit or oil, as lipid sources, would enhance carotenoid absorption in humans. The study found that the addition of both avocado fruit and oil significantly enhanced the subjects' absorption of all carotenoids tested (α-carotene, β-carotene, lycopene, and lutein).

Properties

Carotenoids belong to the category of tetraterpenoid
Tetraterpenoid
Tetraterpenoids are terpenoids of 8 isoprene units - hence 40 carbon atoms in the skeleton.Notable subgroups are*carotenoidsOthers*trianthenol 1*methyl tortuoate C from coral...

s (i.e. they contain 40 carbon atoms, being built from four terpene
Terpene
Terpenes are a large and diverse class of organic compounds, produced by a variety of plants, particularly conifers, though also by some insects such as termites or swallowtail butterflies, which emit terpenes from their osmeterium. They are often strong smelling and thus may have had a protective...

 units each containing 10 carbon atoms). Structurally, carotenoids take the form of a polyene
Polyene
Polyenes are poly-unsaturated organic compounds that contain one or more sequences of alternating double and single carbon-carbon bonds. These double carbon-carbon bonds interact in a process known as conjugation, which results in an overall lower energy state of the molecule.Organic compounds with...

 hydrocarbon chain which is sometimes terminated by rings, and may or may not have additional oxygen atoms attached.
  • Carotenoids with molecules containing oxygen, such as lutein
    Lutein
    Lutein is a xanthophyll and one of 600 known naturally occurring carotenoids. Lutein is synthesized only by plants and like other xanthophylls is found in high quantities in green leafy vegetables such as spinach and kale...

     and zeaxanthin
    Zeaxanthin
    Zeaxanthin is one of the most common carotenoid alcohols found in nature. It is important in the xanthophyll cycle. Synthesized in plants & some micro-organisms, it is the pigment that gives paprika , corn, saffron, and many other plants & microbes their characteristic color.The name is derived...

    , are known as xanthophyll
    Xanthophyll
    Xanthophylls are yellow pigments that form one of two major divisions of the carotenoid group. The name is from Greek xanthos + phyllon , due to their formation of the yellow band seen in early chromatography of leaf pigments...

    s
    .
  • The unoxygenated (oxygen free) carotenoids such as α-carotene
    Alpha-carotene
    α-Carotene is a form of carotene with a β-ring at one end and an ε-ring at the other. It is the second most common form of carotene.-Human physiology:...

    , β-carotene
    Beta-carotene
    β-Carotene is a strongly-coloured red-orange pigment abundant in plants and fruits. It is an organic compound and chemically is classified as a hydrocarbon and specifically as a terpenoid , reflecting its derivation from isoprene units...

     and lycopene
    Lycopene
    Lycopene is a bright red carotene and carotenoid pigment and phytochemical found in tomatoes and other red fruits and vegetables, such as red carrots, watermelons and papayas...

     are known as carotene
    Carotene
    The term carotene is used for several related unsaturated hydrocarbon substances having the formula C40Hx, which are synthesized by plants but cannot be made by animals. Carotene is an orange photosynthetic pigment important for photosynthesis. Carotenes are all coloured to the human eye...

    s
    . Carotenes typically contain only carbon and hydrogen (i.e., are hydrocarbon
    Hydrocarbon
    In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons from which one hydrogen atom has been removed are functional groups, called hydrocarbyls....

    s), and are in the subclass of unsaturated hydrocarbon
    Unsaturated hydrocarbon
    Unsaturated hydrocarbons are hydrocarbons that have double or triple covalent bonds between adjacent carbon atoms. Those with at least one double bond are called alkenes and those with at least one triple bond are called alkynes...

    s.


Probably the most well-known carotenoid is the one that gives this second group its name, carotene
Carotene
The term carotene is used for several related unsaturated hydrocarbon substances having the formula C40Hx, which are synthesized by plants but cannot be made by animals. Carotene is an orange photosynthetic pigment important for photosynthesis. Carotenes are all coloured to the human eye...

, found in carrots (also apricots) and are responsible for their bright orange colour. Crude palm oil, however, is the richest source of carotenoids in nature in terms of retinol (provitamin A) equivalent. Vietnamese Gac
Gac
Momordica cochinchinensis is a Southeast Asian fruit found throughout the region from Southern China to Northeastern Australia.-Etymology:It is commonly known as gac, from the Vietnamese gấc or quả gấc...

 fruit contains the highest known concentration of the carotenoid lycopene
Lycopene
Lycopene is a bright red carotene and carotenoid pigment and phytochemical found in tomatoes and other red fruits and vegetables, such as red carrots, watermelons and papayas...

.

Their colour, ranging from pale yellow through bright orange to deep red, is directly linked to their structure. Xanthophylls are often yellow, hence their class name. The double carbon-carbon bonds interact with each other in a process called conjugation
Conjugated system
In chemistry, a conjugated system is a system of connected p-orbitals with delocalized electrons in compounds with alternating single and multiple bonds, which in general may lower the overall energy of the molecule and increase stability. Lone pairs, radicals or carbenium ions may be part of the...

, which allows electrons in the molecule to move freely across these areas of the molecule. As the number of double bonds increases, electrons associated with conjugated systems have more room to move, and require less energy to change states. This causes the range of energies of light absorbed by the molecule to decrease. As more frequencies of light are absorbed from the short end of the visible spectrum, the compounds acquire an increasingly red appearance.

Physiological effects

In photosynthetic
Photosynthesis
Photosynthesis is a chemical process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs, since they can...

 organisms, specifically flora
Flora
Flora is the plant life occurring in a particular region or time, generally the naturally occurring or indigenous—native plant life. The corresponding term for animals is fauna.-Etymology:...

, carotenoids play a vital role in the photosynthetic reaction centre. They either participate in the energy-transfer process, or protect the reaction center from auto-oxidation. In non-photosynthesizing organisms, specifically human
Human
Humans are the only living species in the Homo genus...

s, carotenoids have been linked to oxidation-preventing mechanisms.
Carotenoids have many physiological functions. Given their structure (above), carotenoids are efficient free-radical scavengers, and they enhance the vertebrate immune system. There are several dozen carotenoids in foods people consume, and most carotenoids have antioxidant activity. Epidemiological
Epidemiology
Epidemiology is the study of health-event, health-characteristic, or health-determinant patterns in a population. It is the cornerstone method of public health research, and helps inform policy decisions and evidence-based medicine by identifying risk factors for disease and targets for preventive...

 studies have shown that people with high β-carotene intake and high plasma levels of β-carotene have a significantly reduced risk of lung cancer
Cancer
Cancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...

. However, studies of supplementation with large doses of β-carotene in smokers have shown an increase in cancer
Cancer
Cancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...

 risk (possibly because excessive β-carotene results in breakdown products that reduce plasma vitamin A
Retinol
Retinol is one of the animal forms of vitamin A. It is a diterpenoid and an alcohol. It is convertible to other forms of vitamin A, and the retinyl ester derivative of the alcohol serves as the storage form of the vitamin in animals....

 and worsen the lung cell proliferation
Cell growth
The term cell growth is used in the contexts of cell development and cell division . When used in the context of cell division, it refers to growth of cell populations, where one cell grows and divides to produce two "daughter cells"...

 induced by smoke). Similar results have been found in other animals. Not all carotenoids are helpful, e.g. etretinate
Etretinate
Etretinate is a medication developed by Hoffmann–La Roche that was approved by the FDA in 1986 to treat severe psoriasis...

 is a teratogen.

Humans and animal
Animal
Animals are a major group of multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously and...

s are mostly incapable of synthesizing carotenoids, and must obtain them through their diet. The notable exception is the red pea aphid, which has the genes
Gênes
Gênes is the name of a département of the First French Empire in present Italy, named after the city of Genoa. It was formed in 1805, when Napoleon Bonaparte occupied the Republic of Genoa. Its capital was Genoa, and it was divided in the arrondissements of Genoa, Bobbio, Novi Ligure, Tortona and...

 necessary for synthesizing carotenoids, thought to have been acquired from fungi via horizontal gene transfer
Horizontal gene transfer
Horizontal gene transfer , also lateral gene transfer , is any process in which an organism incorporates genetic material from another organism without being the offspring of that organism...

. Carotenoids are a common and often ornamental feature in animals. For example, the pink colour of flamingo
Flamingo
Flamingos or flamingoes are gregarious wading birds in the genus Phoenicopterus , the only genus in the family Phoenicopteridae...

s and salmon
Salmon
Salmon is the common name for several species of fish in the family Salmonidae. Several other fish in the same family are called trout; the difference is often said to be that salmon migrate and trout are resident, but this distinction does not strictly hold true...

, and the red colouring of cooked lobster
Lobster
Clawed lobsters comprise a family of large marine crustaceans. Highly prized as seafood, lobsters are economically important, and are often one of the most profitable commodities in coastal areas they populate.Though several groups of crustaceans are known as lobsters, the clawed lobsters are most...

s are due to carotenoids. It has been proposed that carotenoids are used in ornamental traits (for extreme examples see puffin
Puffin
Puffins are any of three small species of auk in the bird genus Fratercula with a brightly coloured beak during the breeding season. These are pelagic seabirds that feed primarily by diving in the water. They breed in large colonies on coastal cliffs or offshore islands, nesting in crevices among...

 birds) because, given their physiological and chemical properties, they can be used as honest indicators of individual health, and hence they can be used by animals when selecting potential mates.

In the macula lutea of the human eye, certain carotenoids are actively concentrated to the point that they cause a yellow coloring, and this may help to protect the retina from blue and actinic light, in the same way that carotenoids protect the photosystems of plants. Carotenoids are also actively concentrated in the corpus luteum
Corpus luteum
The corpus luteum is a temporary endocrine structure in mammals, involved in production of relatively high levels of progesterone and moderate levels of estradiol and inhibin A...

 of the ovaries, where they impart the characteristic color, and may act as general antioxidants.
The most common carotenoids include lycopene and the vitamin A precursor β-carotene. In plants, the xanthophyll lutein
Lutein
Lutein is a xanthophyll and one of 600 known naturally occurring carotenoids. Lutein is synthesized only by plants and like other xanthophylls is found in high quantities in green leafy vegetables such as spinach and kale...

 is the most abundant carotenoid and its role in preventing age-related eye disease is currently under investigation. Lutein and the other carotenoid pigments found in mature leaves are often not obvious because of the presence of chlorophyll
Chlorophyll
Chlorophyll is a green pigment found in almost all plants, algae, and cyanobacteria. Its name is derived from the Greek words χλωρος, chloros and φύλλον, phyllon . Chlorophyll is an extremely important biomolecule, critical in photosynthesis, which allows plants to obtain energy from light...

. However, when chlorophyll is not present, as in young foliage and also dying deciduous
Deciduous
Deciduous means "falling off at maturity" or "tending to fall off", and is typically used in reference to trees or shrubs that lose their leaves seasonally, and to the shedding of other plant structures such as petals after flowering or fruit when ripe...

 foliage (such as autumn leaves), the yellows, reds, and oranges of the carotenoids are predominant. For the same reason, carotenoid colours often predominate in ripe fruit (e.g., oranges, tomatoes, bananas), after being unmasked by the disappearance of chlorophyll.

Aroma chemicals

Products of carotenoid degradation such as ionone
Ionone
The ionones are a series of closely related chemical substances that are part of a group of compounds known as rose ketones, which also includes damascones and damascenones. Ionones are aroma compounds found in a variety of essential oils, including rose oil...

s, damascone
Damascone
Damascones are a series of closely related chemical compounds that are components of a variety of essential oils. The damascones belong to a family of chemicals known as rose ketones, which also includes damascenones and ionones...

s and damascenone
Damascenone
Damascenones are a series of closely related chemical compounds that are components of a variety of essential oils. The damascenones belong to a family of chemicals known as rose ketones, which also includes damascones and ionones...

s are also important fragrance chemicals that are used extensively in the perfume
Perfume
Perfume is a mixture of fragrant essential oils and/or aroma compounds, fixatives, and solvents used to give the human body, animals, objects, and living spaces "a pleasant scent"...

s and fragrance industry. Both β-damascenone and β-ionone although low in concentration in rose
Rose
A rose is a woody perennial of the genus Rosa, within the family Rosaceae. There are over 100 species. They form a group of erect shrubs, and climbing or trailing plants, with stems that are often armed with sharp prickles. Flowers are large and showy, in colours ranging from white through yellows...

 distillates are the key odour-contributing compounds in flowers. In fact, the sweet floral smells present in black tea
Black tea
Black tea is a variety of tea that is more oxidized than the oolong, green, and white varieties.All four varieties are made from leaves of the shrub Camellia sinensis. Black tea is generally stronger in flavor and contains more caffeine than the less oxidized teas. Two principal varieties of the...

, aged tobacco
Tobacco
Tobacco is an agricultural product processed from the leaves of plants in the genus Nicotiana. It can be consumed, used as a pesticide and, in the form of nicotine tartrate, used in some medicines...

, grape
Grape
A grape is a non-climacteric fruit, specifically a berry, that grows on the perennial and deciduous woody vines of the genus Vitis. Grapes can be eaten raw or they can be used for making jam, juice, jelly, vinegar, wine, grape seed extracts, raisins, molasses and grape seed oil. Grapes are also...

, and many fruits are due to the aromatic compounds resulting from carotenoid breakdown.

Disease

Some carotenoids are produced by bacteria to protect themselves from oxidative immune attack. The golden pigment that gives some strains of S. aureus
Staphylococcus aureus
Staphylococcus aureus is a facultative anaerobic Gram-positive coccal bacterium. It is frequently found as part of the normal skin flora on the skin and nasal passages. It is estimated that 20% of the human population are long-term carriers of S. aureus. S. aureus is the most common species of...

their name (aureusis = golden) is a carotenoid called staphyloxanthin
Staphyloxanthin
Staphyloxanthin is a carotenoid pigment that is produced by some strains of Staphylococcus aureus. It acts as a virulence factor. It has an antioxidant action that helps the microbe evade death by reactive oxygen species produced by the host immune system. Staphyloxanthin is responsible for S....

. This carotenoid is a virulence factor with an antioxidant
Antioxidant
An antioxidant is a molecule capable of inhibiting the oxidation of other molecules. Oxidation is a chemical reaction that transfers electrons or hydrogen from a substance to an oxidizing agent. Oxidation reactions can produce free radicals. In turn, these radicals can start chain reactions. When...

 action that helps the microbe evade death by reactive oxygen species
Reactive oxygen species
Reactive oxygen species are chemically reactive molecules containing oxygen. Examples include oxygen ions and peroxides. Reactive oxygen species are highly reactive due to the presence of unpaired valence shell electrons....

 used by the host immune system.

Question of synthesis in the corpus luteum

Following a 1968 report that beta-carotene was synthesized in laboratory conditions in slices of corpus luteum
Corpus luteum
The corpus luteum is a temporary endocrine structure in mammals, involved in production of relatively high levels of progesterone and moderate levels of estradiol and inhibin A...

 from cows, an organ known to concentrates beta-carotene (hence its color and name), attempts have been made to replicate these findings, but have not succeeded. The idea is not presently accepted by the scientific community. Rather, the mammalian corpus luteum, like the macula lutea in the retina
Retina
The vertebrate retina is a light-sensitive tissue lining the inner surface of the eye. The optics of the eye create an image of the visual world on the retina, which serves much the same function as the film in a camera. Light striking the retina initiates a cascade of chemical and electrical...

 of the mammalian eye, merely concentrates carotenoids from the diet.

Artificial synthesis

Microorganisms (using patented gene sequences )can be used to produce C40 carotenoids that are more pure than naturally derived carotenoids. These include lycopene and beta carotene.

List of naturally occurring carotenoids

  • Hydrocarbons
    • Lycopersene 7,8,11,12,15,7',8',11',12',15'-Decahydro-γ,γ-carotene
    • Phytofluene
      Phytofluene
      Phytofluene is a carotenoid pigment with an orange color found naturally in tomatoes and other vegetables. It is the second product of carotenoid biosynthesis. It is formed from phytoene in a desaturation reaction leading to the formation of five conjugated double bonds...

    • Hexahydrolycopene 15-cis-7,8,11,12,7',8'-Hexahydro-γ,γ-carotene
    • Torulene
      Torulene
      Torulene is a carotene which is notable for being synthesized by red pea aphids , imparting the natural red color to the aphids, which aids in their camouflage and escape from predation...

      3',4'-Didehydro-β,γ-carotene
    • α-Zeacarotene 7',8'-Dihydro-ε,γ-carotene

  • Alcohols
    • Alloxanthin
    • Cynthiaxanthin
    • Pectenoxanthin
    • Cryptomonaxanthin (3R,3'R)-7,8,7',8'-Tetradehydro-β,β-carotene-3,3'-diol
    • Crustaxanthin β,-Carotene-3,4,3',4'-tetrol
    • Gazaniaxanthin (3R)-5'-cis-β,γ-Caroten-3-ol
    • OH-Chlorobactene 1',2'-Dihydro-f,γ-caroten-1'-ol
    • Loroxanthin β,ε-Carotene-3,19,3'-triol
    • Lycoxanthin γ,γ-Caroten-16-ol
    • Rhodopin 1,2-Dihydro-γ,γ-caroten-l-ol
    • Rhodopinol aka Warmingol  13-cis-1,2-Dihydro-γ,γ-carotene-1,20-diol
    • Saproxanthin 3',4'-Didehydro-1',2'-dihydro-β,γ-carotene-3,1'-diol
    • Zeaxanthin
      Zeaxanthin
      Zeaxanthin is one of the most common carotenoid alcohols found in nature. It is important in the xanthophyll cycle. Synthesized in plants & some micro-organisms, it is the pigment that gives paprika , corn, saffron, and many other plants & microbes their characteristic color.The name is derived...


  • Glycosides
    • Oscillaxanthin 2,2'-Bis(β-L-rhamnopyranosyloxy)-3,4,3',4'-tetradehydro-1,2,1',2'-tetrahydro-γ,γ-carotene-1,1'-diol
    • Phleixanthophyll 1'-(β-D-Glucopyranosyloxy)-3',4'-didehydro-1',2'-dihydro-β,γ-caroten-2'-ol

  • Ethers
    • Rhodovibrin 1'-Methoxy-3',4'-didehydro-1,2,1',2'-tetrahydro-γ,γ-caroten-1-ol
    • Spheroidene 1-Methoxy-3,4-didehydro-1,2,7',8'-tetrahydro-γ,γ-carotene

  • Epoxides
    • Diadinoxanthin 5,6-Epoxy-7',8'-didehydro-5,6-dihydro—carotene-3,3-diol
    • Luteoxanthin 5,6: 5',8'-Diepoxy-5,6,5',8'-tetrahydro-β,β-carotene-3,3'-diol
    • Mutatoxanthin
    • Citroxanthin
    • Zeaxanthin
      Zeaxanthin
      Zeaxanthin is one of the most common carotenoid alcohols found in nature. It is important in the xanthophyll cycle. Synthesized in plants & some micro-organisms, it is the pigment that gives paprika , corn, saffron, and many other plants & microbes their characteristic color.The name is derived...

       furanoxide 5,8-Epoxy-5,8-dihydro-β,β-carotene-3,3'-diol
    • Neochrome  5',8'-Epoxy-6,7-didehydro-5,6,5',8'-tetrahydro-β,β-carotene-3,5,3'-triol
    • Foliachrome
    • Trollichrome
    • Vaucheriaxanthin 5',6'-Epoxy-6,7-didehydro-5,6,5',6'-tetrahydro-β,β-carotene-3,5,19,3'-tetrol

  • Aldehydes
    • Rhodopinal
    • Wamingone 13-cis-1-Hydroxy-1,2-dihydro-γ,γ-caroten-20-al
    • Torularhodinaldehyde 3',4'-Didehydro-β,γ-caroten-16'-al

  • Acids and Acid Esters
    • Torularhodin 3',4'-Didehydro-β,γ-caroten-16'-oic acid
    • Torularhodin methyl ester Methyl 3',4'-didehydro-β,γ-caroten-16'-oate

  • Ketones
    • Astaxanthin
      Astaxanthin
      Astaxanthin is a carotenoid. It belongs to a larger class of phytochemicals known as terpenes. It is classified as a xanthophyll, which means "yellow leaves". Like many carotenoids, it is a colorful, lipid-soluble pigment. Astaxanthin is found in microalgae, yeast, salmon, trout, krill, shrimp,...

    • Canthaxanthin
      Canthaxanthin
      Canthaxanthin is a carotenoid pigment widely distributed in nature. Carotenoids belong to a larger class of phytochemicals known as terpenoids. The chemical formula of canthaxanthin is C40H52O2. It has E number E161g and is approved for use in the EU and USA however it is not approved for usage in...

       aka Aphanicin, Chlorellaxanthin β,β-Carotene-4,4'-dione
    • Capsanthin (3R,3'S,5'R)-3,3'-Dihydroxy-β,κ-caroten-6'-one
    • Capsorubin (3S,5R,3'S,5'R)-3,3'-Dihydroxy-κ,κ-carotene-6,6'-dione
    • Cryptocapsin (3'R,5'R)-3'-Hydroxy-β,κ-caroten-6'-one
    • 2,2'-Diketospirilloxanthin 1,1'-Dimethoxy-3,4,3',4'-tetradehydro-1,2,1',2'-tetrahydro-γ,γ-carotene-2,2'-dione
    • Flexixanthin 3,1'-Dihydroxy-3',4'-didehydro-1',2'-dihydro-β,γ-caroten-4-one
    • 3-OH-Canthaxanthin aka Adonirubin aka Phoenicoxanthin 3-Hydroxy-β,β-carotene-4,4'-dione
    • Hydroxyspheriodenone 1'-Hydroxy-1-methoxy-3,4-didehydro-1,2,1',2',7',8'-hexahydro-γ,γ-caroten-2-one
    • Okenone 1'-Methoxy-1',2'-dihydro-c,γ-caroten-4'-one
    • Pectenolone 3,3'-Dihydroxy-7',8'-didehydro-β,β-caroten-4-one
    • Phoeniconone aka Dehydroadonirubin 3-Hydroxy-2,3-didehydro-β,β-carotene-4,4'-dione
    • Phoenicopterone β,ε-caroten-4-one
    • Rubixanthone 3-Hydroxy-β,γ-caroten-4'-one
    • Siphonaxanthin 3,19,3'-Trihydroxy-7,8-dihydro-β,ε-caroten-8-one

  • Esters of Alcohols
    • Astacein 3,3'-Bispalmitoyloxy-2,3,2',3'-tetradehydro-β,β-carotene-4,4'-dione or 3,3'-dihydroxy-2,3,2',3'-tetradehydro-β,β-carotene-4,4'-dione dipalmitate
    • Fucoxanthin
      Fucoxanthin
      Fucoxanthin is a xanthophyll, with formula C42H58O6. It is found as an accessory pigment in the chloroplasts of brown algae and most other heterokonts, giving them a brown or olive-green color...

      3'-Acetoxy-5,6-epoxy-3,5'-dihydroxy-6',7'-didehydro-5,6,7,8,5',6'-hexahydro-β,β-caroten-8-one
    • Isofucoxanthin 3'-Acetoxy-3,5,5'-trihydroxy-6',7'-didehydro-5,8,5',6'-tetrahydro-β,β-caroten-8-one
    • Physalien
    • Zeaxanthin
      Zeaxanthin
      Zeaxanthin is one of the most common carotenoid alcohols found in nature. It is important in the xanthophyll cycle. Synthesized in plants & some micro-organisms, it is the pigment that gives paprika , corn, saffron, and many other plants & microbes their characteristic color.The name is derived...

       dipalmitate (3R,3'R)-3,3'-Bispalmitoyloxy-β,β-carotene or (3R,3'R)-β,β-carotene-3,3'-diol dipalmitate
    • Siphonein 3,3'-Dihydroxy-19-lauroyloxy-7,8-dihydro-β,ε-caroten-8-one or 3,19,3'-trihydroxy-7,8-dihydro-β,ε-caroten-8-one 19-laurate

  • Apo Carotenoids
    • β-Apo-2'-carotenal 3',4'-Didehydro-2'-apo-b-caroten-2'-al
    • Apo-2-lycopenal
    • Apo-6'-lycopenal 6'-Apo-y-caroten-6'-al
    • Azafrinaldehyde 5,6-Dihydroxy-5,6-dihydro-10'-apo-β-caroten-10'-al
    • Bixin
      Bixin
      Bixin is an apocarotenoid found in annatto, a natural food coloring obtained from the seeds of the achiote tree . Annatto seeds contain about 5% pigments, which consist of 70-80% bixin....

      6'-Methyl hydrogen 9'-cis-6,6'-diapocarotene-6,6'-dioate
    • Citranaxanthin
      Citranaxanthin
      Citranaxanthin is a carotenoid pigment used as a food additive under the E number E161i as a food coloring. There are natural sources of citranaxanthin, but it is generally prepared synthetically. It is used as an animal feed additive to impart a yellow color to chicken fat and egg yolks....

      5',6'-Dihydro-5'-apo-β-caroten-6'-one or 5',6'-dihydro-5'-apo-18'-nor-β-caroten-6'-one or 6'-methyl-6'-apo-β-caroten-6'-one
    • Crocetin
      Crocetin
      Crocetin is a natural carotenoid dicarboxylic acid that is found in the crocus flower and Gardenia jasminoides . It forms brick red crystals with a melting point of 285 °C....

      8,8'-Diapo-8,8'-carotenedioic acid
    • Crocetinsemialdehyde 8'-Oxo-8,8'-diapo-8-carotenoic acid
    • Crocin
      Crocin
      Crocin is a natural carotenoid chemical compound that is found in the flowers crocus and gardenia. It is the diester formed from the disaccharide gentiobiose and the dicarboxylic acid crocetin. It has a deep red color and forms crystals with a melting point of 186 °C...

      Digentiobiosyl 8,8'-diapo-8,8'-carotenedioate
    • Hopkinsiaxanthin 3-Hydroxy-7,8-didehydro-7',8'-dihydro-7'-apo-b-carotene-4,8'-dione or 3-hydroxy-8'-methyl-7,8-didehydro-8'-apo-b-carotene-4,8'-dione
    • Methyl apo-6'-lycopenoate Methyl 6'-apo-y-caroten-6'-oate
    • Paracentrone 3,5-Dihydroxy-6,7-didehydro-5,6,7',8'-tetrahydro-7'-apo-b-caroten-8'-one or 3,5-dihydroxy-8'-methyl-6,7-didehydro-5,6-dihydro-8'-apo-b-caroten-8'-one
    • Sintaxanthin 7',8'-Dihydro-7'-apo-b-caroten-8'-one or 8'-methyl-8'-apo-b-caroten-8'-one

  • Nor and Seco Carotenoids
    • Actinioerythrin 3,3'-Bisacyloxy-2,2'-dinor-b,b-carotene-4,4'-dione
    • β-Carotenone 5,6:5',6'-Diseco-b,b-carotene-5,6,5',6'-tetrone
    • Peridinin
      Peridinin
      Peridinin is a light-harvesting carotenoid, a pigment associated with chlorophyll and found in the peridinin-chlorophyll-protein light-harvesting complex in dinoflagellates, best studied in Amphidinium carterae...

      3'-Acetoxy-5,6-epoxy-3,5'-dihydroxy-6',7'-didehydro-5,6,5',6'-tetrahydro-12',13',20'-trinor-b,b-caroten-19,11-olide
    • Pyrrhoxanthininol 5,6-epoxy-3,3'-dihydroxy-7',8'-didehydro-5,6-dihydro-12',13',20'-trinor-b,b-caroten-19,11-olide
    • Semi-α-carotenone 5,6-Seco-b,e-carotene-5,6-dione
    • Semi-β-carotenone 5,6-seco-b,b-carotene-5,6-dione or 5',6'-seco-b,b-carotene-5',6'-dione
    • Triphasiaxanthin 3-Hydroxysemi-b-carotenone 3'-Hydroxy-5,6-seco-b,b-carotene-5,6-dione or 3-hydroxy-5',6'-seco-b,b-carotene-5',6'-dione

  • retro Carotenoids and retro Apo Carotenoids

    • Eschscholtzxanthin 4',5'-Didehydro-4,5'-retro-b,b-carotene-3,3'-diol
    • Eschscholtzxanthone 3'-Hydroxy-4',5'-didehydro-4,5'-retro-b,b-caroten-3-one
    • Rhodoxanthin
      Rhodoxanthin
      Rhodoxanthin is a xanthophyll pigment with a purple color that is found in small quantities in a variety plants including Taxus baccata. It is also found in the feathers of some birds...

      4',5'-Didehydro-4,5'-retro-b,b-carotene-3,3'-dione
    • Tangeraxanthin 3-Hydroxy-5'-methyl-4,5'-retro-5'-apo-b-caroten-5'-one or 3-hydroxy-4,5'-retro-5'-apo-b-caroten-5'-one

  • Higher Carotenoids
    • Nonaprenoxanthin 2-(4-Hydroxy-3-methyl-2-butenyl)-7',8',11',12'-tetrahydro-e,y-carotene
    • Decaprenoxanthin 2,2'-Bis(4-hydroxy-3-methyl-2-butenyl)-e,e-carotene
  • C.p. 450 2-[4-Hydroxy-3-(hydroxymethyl)-2-butenyl]-2'-(3-methyl-2-butenyl)-b,b-carotene
    • C.p. 473 2'-(4-Hydroxy-3-methyl-2-butenyl)-2-(3-methyl-2-butenyl)-3',4'-didehydro-l',2'-dihydro-b,y-caroten-1'-ol
    • Bacterioruberin 2,2'-Bis(3-hydroxy-3-methylbutyl)-3,4,3',4'-tetradehydro-1,2,1',2'-tetrahydro-y,y-carotene-1,1'-dio

Classifications

Carotenoids can have many classifications. Some are alcohols, hydrocarbons, ethers, epoxides, ketones, acids, etc. They can be classified also into apo Carotenoids, nor and seco Carotenoids, retro Carotenoids, retro apo carotenoids and "Higher Carotenoids."

External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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