The term carotene (also carotin, from the Latin ''carota'', "carrot") is used for many related unsaturated hydrocarbon substances having the formula C₄₀H_x, which are synthesized by plants but in general cannot be made by animals (with the exception of some

aphid Aphids are small sap-sucking insects in the Taxonomic rank, family Aphididae. Common names include greenfly and blackfly, although individuals within a species can vary widely in color. The group includes the fluffy white Eriosomatinae, woolly ...

s and

spider mite Spider mites are members of the family Tetranychidae, which includes about 1,200 species. They are part of the subclass Acari (mites). Spider mites generally live on the undersides of leaves of plants, where they may spin protective silk webs, a ...

s which acquired the synthesizing genes from fungi). Carotenes are

photosynthetic pigment A photosynthetic pigment (accessory pigment; chloroplast pigment; antenna pigment) is a pigment that is present in chloroplasts or photosynthetic bacteria and captures the light energy necessary for photosynthesis. List of photosynthetic pigmen ...

s important for

photosynthesis Photosynthesis ( ) is a system of biological processes by which photosynthetic organisms, such as most plants, algae, and cyanobacteria, convert light energy, typically from sunlight, into the chemical energy necessary to fuel their metabo ...

. Carotenes contain no oxygen atoms. They absorb ultraviolet, violet, and blue light and scatter orange or red light, and yellow light(in low concentrations). Carotenes are responsible for the orange colour of the

carrot The carrot ('' Daucus carota'' subsp. ''sativus'') is a root vegetable, typically orange in colour, though heirloom variants including purple, black, red, white, and yellow cultivars exist, all of which are domesticated forms of the wild ...

, after which this class of chemicals is named, and for the colours of many other fruits, vegetables and fungi (for example,

sweet potato The sweet potato or sweetpotato (''Ipomoea batatas'') is a dicotyledonous plant in the morning glory family, Convolvulaceae. Its sizeable, starchy, sweet-tasting tuberous roots are used as a root vegetable, which is a staple food in parts of ...

es,

chanterelle Chanterelle is the common name of several species of fungi in the genera ''Cantharellus'', ''Craterellus'', ''Gomphus (fungus), Gomphus'', and ''Polyozellus''. They are orange, yellow or white, meaty and funnel-shaped. On the lower surface, mos ...

and orange

cantaloupe The cantaloupe ( ) is a type of true melon (''Cucumis melo'') with sweet, aromatic, and usually orange flesh. Originally, ''cantaloupe'' refers to the true cantaloupe or European cantaloupe with non- to slightly netted and often ribbed rind. ...

melon). Carotenes are also responsible for the orange (but not all of the yellow) colours in dry foliage. They also (in lower concentrations) impart the yellow coloration to milk-fat and butter. Omnivorous animal species which are relatively poor converters of coloured dietary

carotenoids Carotenoids () are yellow, orange, and red organic compound, organic pigments that are produced by plants and algae, as well as several bacteria, archaea, and Fungus, fungi. Carotenoids give the characteristic color to pumpkins, carrots, parsnips ...

to colourless retinoids, such as humans and

chicken The chicken (''Gallus gallus domesticus'') is a domesticated subspecies of the red junglefowl (''Gallus gallus''), originally native to Southeast Asia. It was first domesticated around 8,000 years ago and is now one of the most common and w ...

s, have yellow-coloured

body fat Adipose tissue (also known as body fat or simply fat) is a loose connective tissue composed mostly of adipocytes. It also contains the stromal vascular fraction (SVF) of cells including preadipocytes, fibroblasts, Blood vessel, vascular endothel ...

, as a result of the carotenoid retention from the vegetable portion of their diet. Carotenes contribute to photosynthesis by transmitting the light energy they absorb to

chlorophyll Chlorophyll is any of several related green pigments found in cyanobacteria and in the chloroplasts of algae and plants. Its name is derived from the Greek words (, "pale green") and (, "leaf"). Chlorophyll allows plants to absorb energy ...

. They also protect plant tissues by helping to absorb the energy from

singlet oxygen Singlet oxygen, systematically named dioxygen(singlet) and dioxidene, is a gaseous inorganic chemistry, inorganic chemical with the formula O=O (also written as or ), which is in a quantum state where all electrons are Radical (chemistry), spin p ...

, an excited form of the oxygen molecule O₂ which is formed during photosynthesis. β-Carotene is composed of two retinyl groups, and is broken down in the

mucosa A mucous membrane or mucosa is a membrane that lines various cavities in the body of an organism and covers the surface of internal organs. It consists of one or more layers of epithelial cells overlying a layer of loose connective tissue. It ...

of the human

small intestine The small intestine or small bowel is an organ (anatomy), organ in the human gastrointestinal tract, gastrointestinal tract where most of the #Absorption, absorption of nutrients from food takes place. It lies between the stomach and large intes ...

β-carotene 15,15'-monooxygenase In enzymology, beta-carotene 15,15'-dioxygenase, () is an enzyme with systematic name ''beta-carotene:oxygen 15,15'-dioxygenase (bond-cleaving)''. In human it is encoded by the ''BCO1'' gene. This enzyme catalyses the following chemical reactio ...

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 ret ...

, a form of

vitamin A 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 not ...

. β-Carotene can be stored in the

liver The liver is a major metabolic organ (anatomy), organ exclusively found in vertebrates, which performs many essential biological Function (biology), functions such as detoxification of the organism, and the Protein biosynthesis, synthesis of var ...

and body fat and converted to retinal as needed, thus making it a form of vitamin A for humans and some other mammals. The carotenes α-carotene and γ-carotene, due to their single retinyl group (β-

ionone The ionones, from greek ἴον ion "violet", 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 ...

ring), also have some vitamin A activity (though less than β-carotene), as does the

xanthophyll Xanthophylls (originally phylloxanthins) are yellow pigments that occur widely in nature and form one of two major divisions of the carotenoid group; the other division is formed by the carotenes. The name is from Greek: (), meaning "yellow", an ...

carotenoid β- cryptoxanthin. All other carotenoids, including

lycopene Lycopene is an organic compound classified as a tetraterpene and a carotene. Lycopene (from the Neo-Latin '' Lycopersicon'', the name of a former tomato genus) is a bright red carotenoid hydrocarbon found in tomatoes and other red fruits and ve ...

, have no beta-ring and thus no vitamin A activity (although they may have antioxidant activity and thus biological activity in other ways). Animal species differ greatly in their ability to convert retinyl (beta-

) containing carotenoids to retinals. Carnivores in general are poor converters of dietary ionone-containing carotenoids. Pure carnivores such as

ferret The ferret (''Mustela furo'') is a small, domesticated species belonging to the family Mustelidae. The ferret is most likely a domesticated form of the wild European polecat (''Mustela putorius''), as evidenced by the ferret's ability to inter ...

s lack β-carotene 15,15'-monooxygenase and cannot convert any carotenoids to retinals at all (resulting in carotenes not being a form of vitamin A for this species); while cats can convert a trace of β-carotene to retinol, although the amount is totally insufficient for meeting their daily retinol needs.

Molecular structure

Carotenes are polyunsaturated

hydrocarbon In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and Hydrophobe, hydrophobic; their odor is usually fain ...

s containing 40 carbon atoms per molecule, variable numbers of hydrogen atoms, and no other elements. Some carotenes are terminated by rings, on one or both ends of the molecule. All are coloured, due to the presence of

conjugated double bond In physical organic chemistry, a conjugated system is a system of connected p-orbitals with delocalized electrons in a molecule, which in general lowers the overall energy of the molecule and increases stability. It is conventionally represent ...

s. Carotenes are

tetraterpene Tetraterpenes are terpenes consisting of eight isoprene units and have the molecular formula C40H64. Tetraterpenoids (including many carotenoids) are tetraterpenes that have been chemically modified, as indicated by the presence of oxygen-contai ...

s, meaning that they are derived from eight 5-carbon

isoprene Isoprene, or 2-methyl-1,3-butadiene, is a common volatile organic compound with the formula CH2=C(CH3)−CH=CH2. In its pure form it is a colorless volatile liquid. It is produced by many plants and animals (including humans) and its polymers ar ...

units (or four 10-carbon terpene units). Carotenes are found in plants in two primary forms designated by characters from the

Greek alphabet The Greek alphabet has been used to write the Greek language since the late 9th or early 8th century BC. It was derived from the earlier Phoenician alphabet, and is the earliest known alphabetic script to systematically write vowels as wel ...

: alpha-carotene (α-carotene) and beta-carotene (β-carotene). Gamma-, delta-, epsilon-, and zeta-carotene (γ, δ, ε, and ζ-carotene) also exist. Since they are hydrocarbons, and therefore contain no oxygen, carotenes are fat-soluble and insoluble in water (in contrast with other

carotenoid Carotenoids () are yellow, orange, and red organic pigments that are produced by plants and algae, as well as several bacteria, archaea, and fungi. Carotenoids give the characteristic color to pumpkins, carrots, parsnips, corn, tomatoes, cana ...

s, the

s, which contain oxygen and thus are less chemically hydrophobic).

History

The discovery of carotene from carrot juice is credited to Heinrich Wilhelm Ferdinand Wackenroder, a finding made during a search for antihelminthics, which he published in 1831. He obtained it in small ruby-red flakes soluble in ether, which when dissolved in fats gave "a beautiful yellow colour".

William Christopher Zeise William Christopher Zeise (15 October 1789 – 12 November 1847) was a Danish organic chemist. He is best known for synthesising one of the first organometallic compounds, named Zeise's salt in his honour. He also performed pioneering studie ...

recognised its hydrocarbon nature in 1847, but his analyses gave him a composition of C₅H₈. It was

Léon-Albert Arnaud Léon-Albert Arnaud (15 February 1853 – 27 March 1915) was a French chemist born in Paris. From 1872 he worked as an assistant in the laboratory of Michel Eugène Chevreul (1786–1889) at the ''Muséum national d'histoire naturelle''. In ...

in 1886 who confirmed its hydrocarbon nature and gave the formula C₂₆H₃₈, which is close to the theoretical composition of C₄₀H₅₆.

Adolf Lieben Adolf Lieben (3 December 1836 – 6 June 1914) was an Austrian Jewish chemist. He was born in Vienna the son of Ignatz Lieben. He studied at the University of Vienna, University of Heidelberg ( Ph.D. 1856 with Robert Wilhelm Bunsen), and Pa ...

in studies, also published in 1886, of the colouring matter in

corpora lutea The corpus luteum (Latin for "yellow body"; : corpora lutea) is a temporary endocrine structure in female ovaries involved in the production of relatively high levels of progesterone, and moderate levels of estradiol, and inhibin A. It is the rema ...

, first came across carotenoids in animal tissue, but did not recognise the nature of the pigment.

Johann Ludwig Wilhelm Thudichum Johann Ludwig Wilhelm Thudichum, also known as John Louis William Thudichum (August 27, 1829, Büdingen – September 7, 1901) was a German-born physician and biochemist. From 1847 he studied medicine at the University of Giessen, where he ...

, in 1868–1869, after stereoscopic spectral examination, applied the term 'luteine' (

lutein Lutein (;"Lutein"

Richard Martin Willstätter, who gained the

Nobel Prize The Nobel Prizes ( ; ; ) are awards administered by the Nobel Foundation and granted in accordance with the principle of "for the greatest benefit to humankind". The prizes were first awarded in 1901, marking the fifth anniversary of Alfred N ...

Chemistry Chemistry is the scientific study of the properties and behavior of matter. It is a physical science within the natural sciences that studies the chemical elements that make up matter and chemical compound, compounds made of atoms, molecules a ...

in 1915, mainly for his work on

, assigned the composition of C₄₀H₅₆, distinguishing it from the similar but oxygenated

, C₄₀H₅₆O₂. With Heinrich Escher, in 1910,

was isolated from tomatoes and shown to be an

isomer In chemistry, isomers are molecules or polyatomic ions with identical molecular formula – that is, the same number of atoms of each element (chemistry), element – but distinct arrangements of atoms in space. ''Isomerism'' refers to the exi ...

of carotene. Later work by Escher also differentiated the '

luteal The corpus luteum (Latin for "yellow body"; : corpora lutea) is a temporary endocrine structure in female ovaries involved in the production of relatively high levels of progesterone, and moderate levels of estradiol, and inhibin A. It is the rema ...

' pigments in egg yolk from that of the carotenes in cow corpus luteum.

Dietary sources

The following foods contain carotenes in notable amounts: *

s * wolfberries (goji) *

mango A mango is an edible stone fruit produced by the tropical tree '' Mangifera indica''. It originated from the region between northwestern Myanmar, Bangladesh, and northeastern India. ''M. indica'' has been cultivated in South and Southeast As ...

es * red bell pepper *

papaya The papaya (, ), papaw, () or pawpaw () is the plant species ''Carica papaya'', one of the 21 accepted species in the genus '' Carica'' of the family Caricaceae, and also the name of its fruit. It was first domesticated in Mesoamerica, within ...

spinach Spinach (''Spinacia oleracea'') is a leafy green flowering plant native to Central Asia, Central and Western Asia. It is of the order Caryophyllales, family Amaranthaceae, subfamily Chenopodioideae. Its leaves are a common vegetable consumed eit ...

kale Kale (), also called leaf cabbage, belongs to a group of cabbage (''Brassica oleracea'') cultivars primarily grown for their Leaf vegetable, edible leaves; it has also been used as an ornamental plant. Its multiple different cultivars vary quite ...

tomato The tomato (, ), ''Solanum lycopersicum'', is a plant whose fruit is an edible Berry (botany), berry that is eaten as a vegetable. The tomato is a member of the nightshade family that includes tobacco, potato, and chili peppers. It originate ...

dandelion greens ''Taraxacum'' () is a genus of flowering plants in the family Asteraceae, which consists of species commonly known as dandelions. The scientific and hobby study of the genus is known as taraxacology. The genus has a near-cosmopolitan distribu ...

broccoli Broccoli (''Brassica oleracea'' var. ''italica'') is an edible green plant in the Brassicaceae, cabbage family (family Brassicaceae, genus ''Brassica'') whose large Pseudanthium, flowering head, plant stem, stalk and small associated leafy gre ...

collard greens Collard is a group of loose-leafed cultivars of ''Brassica oleracea'' (the same species as many common vegetables like cabbage and broccoli). Part of the acephala cultivar group (or kale group), collard is also classified as the variety ''B.& ...

winter squash Winter squash is an annual fruit representing several squash species within the genus '' Cucurbita''. Late-growing, less symmetrical, odd-shaped, rough or warty varieties, small to medium in size, but with long-keeping qualities and hard rinds, ...

pumpkin A pumpkin is a cultivar, cultivated winter squash in the genus ''Cucurbita''. The term is most commonly applied to round, orange-colored squash varieties, but does not possess a scientific definition. It may be used in reference to many dif ...

cassava ''Manihot esculenta'', common name, commonly called cassava, manioc, or yuca (among numerous regional names), is a woody shrub of the spurge family, Euphorbiaceae, native to South America, from Brazil, Paraguay and parts of the Andes. Although ...

Absorption from these foods is enhanced if eaten with fats, as carotenes are fat soluble, and if the food is cooked for a few minutes until the plant

cell wall A cell wall is a structural layer that surrounds some Cell type, cell types, found immediately outside the cell membrane. It can be tough, flexible, and sometimes rigid. Primarily, it provides the cell with structural support, shape, protection, ...

splits and the color is released into any liquid. 12 μg of dietary β-carotene supplies the equivalent of 1 μg of retinol, and 24 μg of α-carotene or β-cryptoxanthin provides the equivalent of 1 μg of retinol.

Forms of carotene

The two primary

s of carotene, α-carotene and β-carotene, differ in the position of a

double bond In chemistry, a double bond is a covalent bond between two atoms involving four bonding electrons as opposed to two in a single bond. Double bonds occur most commonly between two carbon atoms, for example in alkenes. Many double bonds exist betw ...

(and thus a hydrogen) in the cyclic group at one end (the right end in the diagram at right). β-Carotene is the more common form and can be found in

yellow Yellow is the color between green and orange on the spectrum of light. It is evoked by light with a dominant wavelength of roughly 575585 nm. It is a primary color in subtractive color systems, used in painting or color printing. In t ...

orange Orange most often refers to: *Orange (fruit), the fruit of the tree species '' Citrus'' × ''sinensis'' ** Orange blossom, its fragrant flower ** Orange juice *Orange (colour), the color of an orange fruit, occurs between red and yellow in the vi ...

, and

green Green is the color between cyan and yellow on the visible spectrum. It is evoked by light which has a dominant wavelength of roughly 495570 nm. In subtractive color systems, used in painting and color printing, it is created by a com ...

leafy

fruit In botany, a fruit is the seed-bearing structure in flowering plants (angiosperms) that is formed from the ovary after flowering. Fruits are the means by which angiosperms disseminate their seeds. Edible fruits in particular have long propaga ...

s and

vegetable Vegetables are edible parts of plants that are consumed by humans or other animals as food. This original meaning is still commonly used, and is applied to plants collectively to refer to all edible plant matter, including edible flower, flo ...

s. As a

rule of thumb In English language, English, the phrase ''rule of thumb'' refers to an approximate method for doing something, based on practical experience rather than theory. This usage of the phrase can be traced back to the 17th century and has been associat ...

, the greater the intensity of the orange colour of the fruit or vegetable, the more β-carotene it contains. Carotene protects plant cells against the destructive effects of ultraviolet light so β-carotene is an

antioxidant Antioxidants are Chemical compound, compounds that inhibit Redox, oxidation, a chemical reaction that can produce Radical (chemistry), free radicals. Autoxidation leads to degradation of organic compounds, including living matter. Antioxidants ...

β-Carotene and physiology

β-Carotene and cancer

An article on the

American Cancer Society The American Cancer Society (ACS) is a nationwide non-profit organization dedicated to eliminating cancer. The ACS publishes the journals ''Cancer'', '' CA: A Cancer Journal for Clinicians'' and '' Cancer Cytopathology''. History The society w ...

says that The Cancer Research Campaign has called for warning labels on β-carotene supplements to caution smokers that such supplements may increase the risk of lung cancer.

The New England Journal of Medicine ''The New England Journal of Medicine'' (''NEJM'') is a weekly medical journal published by the Massachusetts Medical Society. Founded in 1812, the journal is among the most prestigious peer-reviewed medical journals. Its 2023 impact factor w ...

published an article in 1994 about a trial which examined the relationship between daily supplementation of β-carotene and

vitamin E Vitamin E is a group of eight compounds related in molecular structure that includes four tocopherols and four tocotrienols. The tocopherols function as fat-soluble antioxidants which may help protect cell membranes from reactive oxygen speci ...

(α-

tocopherol Tocopherols (; TCP) are a class of organic compounds comprising various methylated phenols, many of which have vitamin E activity. Because the vitamin activity was first identified in 1936 from a dietary fertility factor in rats, it was named ''t ...

) and the incidence of lung cancer. The study was done using supplements and researchers were aware of the epidemiological correlation between carotenoid-rich fruits and vegetables and lower lung cancer rates. The research concluded that no reduction in lung cancer was found in the participants using these supplements, and furthermore, these supplements may, in fact, have harmful effects. The Journal of the

National Cancer Institute The National Cancer Institute (NCI) coordinates the United States National Cancer Program and is part of the National Institutes of Health (NIH), which is one of eleven agencies that are part of the U.S. Department of Health and Human Services. ...

and The New England Journal of Medicine published articles in 1996 about a trial with a goal to determine if vitamin A (in the form of

retinyl palmitate Retinyl palmitate, or vitamin A palmitate, is the ester of retinol (vitamin A) and palmitic acid, with formula C36H60O2. It is the most abundant form of vitamin A storage in animals. An alternate spelling, retinol palmitate, which violates the - ...

) and β-carotene (at about 30 mg/day, which is 10 times the

Reference Daily Intake In the U.S. and Canada, the Reference Daily Intake (RDI) is used in nutrition labeling on food and dietary supplement products to indicate the daily intake level of a nutrient that is considered to be sufficient to meet the requirements of 97� ...

) supplements had any beneficial effects to prevent cancer. The results indicated an ''increased'' risk of lung and prostate cancers for the participants who consumed the β-carotene supplement and who had lung irritation from

smoking Smoking is a practice in which a substance is combusted, and the resulting smoke is typically inhaled to be tasted and absorbed into the bloodstream of a person. Most commonly, the substance used is the dried leaves of the tobacco plant, whi ...

asbestos Asbestos ( ) is a group of naturally occurring, Toxicity, toxic, carcinogenic and fibrous silicate minerals. There are six types, all of which are composed of long and thin fibrous Crystal habit, crystals, each fibre (particulate with length su ...

exposure, causing the trial to be stopped early. A review of all randomized controlled trials in the scientific literature by the

Cochrane Collaboration Cochrane is a British international charitable organisation formed to synthesize medical research findings to facilitate evidence-based choices about health interventions involving health professionals, patients and policy makers. It includes ...

published in ''

JAMA ''JAMA'' (''The Journal of the American Medical Association'') is a peer-reviewed medical journal published 48 times a year by the American Medical Association. It publishes original research, reviews, and editorials covering all aspects of b ...

'' in 2007 found that synthetic β-carotene ''increased'' mortality by 1–8% (Relative Risk 1.05, 95% confidence interval 1.01–1.08). However, this meta-analysis included two large studies of smokers, so it is not clear that the results apply to the general population. The review only studied the influence of synthetic antioxidants and the results should not be translated to potential effects of fruits and vegetables.

β-Carotene and photosensitivity

Oral β-carotene is prescribed to people suffering from

erythropoietic protoporphyria Erythropoietic protoporphyria (or commonly called EPP) is a form of porphyria, which varies in severity and can be very painful. It arises from a deficiency in the enzyme ferrochelatase, leading to abnormally high levels of protoporphyrin in the ...

. It provides them some relief from photosensitivity.

Carotenemia

Carotenemia or hypercarotenemia is excess carotene, but unlike excess vitamin A, carotene is non-toxic. Although hypercarotenemia is not particularly dangerous, it can lead to an oranging of the skin (carotenodermia), but not the

conjunctiva In the anatomy of the eye, the conjunctiva (: conjunctivae) is a thin mucous membrane that lines the inside of the eyelids and covers the sclera (the white of the eye). It is composed of non-keratinized, stratified squamous epithelium with gobl ...

of eyes (thus easily distinguishing it visually from

jaundice Jaundice, also known as icterus, is a yellowish or, less frequently, greenish pigmentation of the skin and sclera due to high bilirubin levels. Jaundice in adults is typically a sign indicating the presence of underlying diseases involving ...

). It is most commonly associated with consumption of an abundance of

s, but it also can be a

medical sign Signs and symptoms are diagnostic indications of an illness, injury, or condition. Signs are objective and externally observable; symptoms are a person's reported subjective experiences. A sign for example may be a higher or lower temperature ...

of more dangerous conditions.

Production

Carotenes are produced in a general manner for other terpenoids and terpenes, i.e. by coupling, cyclization, and oxygenation reactions of

derivatives.

Lycopene Lycopene is an organic compound classified as a tetraterpene and a carotene. Lycopene (from the Neo-Latin '' Lycopersicon'', the name of a former tomato genus) is a bright red carotenoid hydrocarbon found in tomatoes and other red fruits and ve ...

is the key precursor to carotenoids. It is formed by coupling of

geranylgeranyl pyrophosphate Geranylgeranyl pyrophosphate is an intermediate in the biosynthesis of diterpenes and diterpenoids. It is also the precursor to carotenoids, gibberellins, tocopherols, and chlorophylls. It is also a precursor to geranylgeranylated proteins, whic ...

and geranyllinally pyrophosphate. Most of the world's synthetic supply of carotene comes from a manufacturing complex located in

Freeport, Texas Freeport is a city in Brazoria County, Texas, United States, located on the Gulf of Mexico, founded in 1912. According to the 2020 United States census, 2020 census, the city population was 10,696, down from 12,049 in 2010, where Hispanic (U.S. ...

and owned by DSM. The other major supplier

BASF BASF SE (), an initialism of its original name , is a European Multinational corporation, multinational company and the List of largest chemical producers, largest chemical producer in the world. Its headquarters are located in Ludwigshafen, Ge ...

also uses a chemical process to produce β-carotene. Together these suppliers account for about 85% of the β-carotene on the market. In Spain Vitatene produces natural β-carotene from fungus ''

Blakeslea trispora ''Blakeslea trispora'' is a mould and member of the division Zygomycota. This species has been well studied for its ability to produce carotenoids, particularly, β-carotene and lycopene. β-carotene is a vitamin A precursor and both of β-carot ...

'', as does DSM but at much lower amount when compared to its synthetic β-carotene operation. In Australia, organic β-carotene is produced by Aquacarotene Limited from dried marine algae ''

Dunaliella salina ''Dunaliella salina'' is a type of halophile unicellular green algae especially found in hypersaline environments, such as salt lakes and salt evaporation ponds. Known for its antioxidant activity because of its ability to create a large amoun ...

'' grown in harvesting ponds situated in

Karratha, Western Australia Karratha is a city in the Pilbara region of Western Australia, adjoining the port of Dampier. It is located in the traditional lands and waters of the Ngarluma people, for whom it has been ( or 'country') for tens of thousands of years. Locat ...

. BASF Australia is also producing β-carotene from microalgae grown in two sites in Australia that are the world's largest algae farms. In

Portugal Portugal, officially the Portuguese Republic, is a country on the Iberian Peninsula in Southwestern Europe. Featuring Cabo da Roca, the westernmost point in continental Europe, Portugal borders Spain to its north and east, with which it share ...

, the

industrial biotechnology Biotechnology is a multidisciplinary field that involves the integration of natural sciences and engineering sciences in order to achieve the application of organisms and parts thereof for products and services. Specialists in the field are kn ...

company Biotrend is producing natural all-''trans''-β-carotene from a non-genetically modified bacteria of the genus ''

Sphingomonas ''Sphingomonas'' was defined in 1990 as a group of Gram-negative, rod-shaped, chemoheterotrophic, strictly Aerobic organism, aerobic bacteria. They possess ubiquinone 10 as their major Electron transport chain#Quinone carriers, respiratory quinon ...

'' isolated from soil. Carotenes are also found in

palm oil Palm oil is an edible vegetable oil derived from the mesocarp (reddish pulp) of the fruit of oil palms. The oil is used in food manufacturing, in beauty products, and as biofuel. Palm oil accounted for about 36% of global oils produced from o ...

, corn, and in the milk of dairy cows, causing cow's milk to be light yellow, depending on the feed of the cattle, and the amount of fat in the milk (high-fat milks, such as those produced by

Guernsey Guernsey ( ; Guernésiais: ''Guernési''; ) is the second-largest island in the Channel Islands, located west of the Cotentin Peninsula, Normandy. It is the largest island in the Bailiwick of Guernsey, which includes five other inhabited isl ...

cows, tend to be yellower because their fat content causes them to contain more carotene). Carotenes are also found in some species of termites, where they apparently have been picked up from the diet of the insects.

Synthesis

There are currently two commonly used methods of

total synthesis Total synthesis, a specialized area within organic chemistry, focuses on constructing complex organic compounds, especially those found in nature, using laboratory methods. It often involves synthesizing natural products from basic, commercially ...

of β-carotene. The first was developed by

and is based on the

Wittig reaction The Wittig reaction or Wittig olefination is a chemical reaction of an aldehyde or ketone with a triphenyl phosphonium ylide called a Wittig reagent. Wittig reactions are most commonly used to convert aldehydes and ketones to alkenes. Most o ...

with Wittig himself as patent holder:Wittig G.; Pommer H.: ''DBP 954247, 1956Wittig G.; Pommer H. (1959). ''Chem. Abstr''. 53: 2279 Wittig-9

The second is a

Grignard reaction The Grignard reaction () is an organometallic chemical reaction in which, according to the classical definition, carbon alkyl, allyl, vinyl, or aryl magnesium halides (Grignard reagent) are added to the carbonyl groups of either an aldehyde or ...

, elaborated by

Hoffman-La Roche F. Hoffmann-La Roche AG, commonly known as Roche (), is a Swiss multinational holding healthcare company that operates worldwide under two divisions: Pharmaceuticals and Diagnostics. Its holding company, Roche Holding AG, has shares listed on ...

from the original synthesis of Inhoffen et al. They are both symmetrical; the BASF synthesis is C20 + C20, and the Hoffman-La Roche synthesis is C19 + C2 + C19.

Nomenclature

Carotenes are

s containing no oxygen. Carotenoids containing some oxygen are known as

s. The two ends of the β-carotene molecule are structurally identical, and are called β-rings. Specifically, the group of nine carbon atoms at each end form a β-ring. The α-carotene molecule has a β-ring at one end; the other end is called an ε-ring. There is no such thing as an "α-ring". These and similar names for the ends of the carotenoid molecules form the basis of a systematic naming scheme, according to which: * α-carotene is β,ε-carotene; * β-carotene is β,β-carotene; * γ-carotene (with one β ring and one uncyclized end that is labelled ''

psi Psi, PSI or Ψ may refer to: Alphabetic letters * Psi (Greek) (Ψ or ψ), the twenty-third letter of the Greek alphabet * Psi (Cyrillic), letter of the early Cyrillic alphabet, adopted from Greek Arts and entertainment * "Psi" as an abbreviat ...

'') is β,ψ-carotene; * δ-carotene (with one ε ring and one uncyclized end) is ε,ψ-carotene; * ε-carotene is ε,ε-carotene *

is ψ,ψ-carotene ζ-Carotene is the

biosynthetic Biosynthesis, i.e., chemical synthesis occurring in biological contexts, is a term most often referring to multi-step, enzyme- catalyzed processes where chemical substances absorbed as nutrients (or previously converted through biosynthesis) serve ...

precursor of

neurosporene Neurosporene is a carotenoid pigment. It is an intermediate in the biosynthesis of lycopene Lycopene is an organic compound classified as a tetraterpene and a carotene. Lycopene (from the Neo-Latin '' Lycopersicon'', the name of a former toma ...

, which is the precursor of lycopene, which, in turn, is the precursor of the carotenes α through ε.

Food additive

Carotene is used to colour products such as juice, cakes, desserts, butter and margarine. It is approved for use as a food additive in the EU (listed as additive E160a) Australia and New Zealand (listed as 160a) and the US.US FDA:

References

External links

* {{Authority control Vitamin A Food colorings Carotenoids Hydrocarbons E-number additives