The term
carotene is used for several related
unsaturated hydrocarbonUnsaturated 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...
substances having the formula C
40H
x, which are synthesized by plants but cannot be made by animals. Carotene is an orange
photosynthetic pigmentA photosynthetic pigment is a pigment that is present in chloroplasts or photosynthetic bacteria and captures the light energy necessary for photosynthesis.- Plants :...
important for
photosynthesisPhotosynthesis 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...
. Carotenes are all coloured to the human eye. They are responsible for the orange colour of the
carrotThe carrot is a root vegetable, usually orange in colour, though purple, red, white, and yellow varieties exist. It has a crisp texture when fresh...
, for which this class of chemicals is named, and for the colours of many other fruits and vegetables (for example, sweet potatoes and orange
cantaloupe"Rockmelon" redirects here, for the band see Rockmelons. See also Cantaloupe .Cantaloupe refers to a variety of Cucumis melo, a species in the family Cucurbitaceae which includes nearly all melons and squashes. Cantaloupes range in size from...
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 colouration to milk-fat and butter. Omnivorous animal species which are relatively poor converters of coloured dietary carotenoids to colourless retinoids have yellowed-coloured body fat, as a result of the carotenoid retention from the vegetable portion of their diet. The typical yellow-coloured fat of humans and chickens is a result of fat storage of carotenes from their diets.
Carotenes contribute to photosynthesis by transmitting the light energy they absorb from
chlorophyllChlorophyll 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...
. They also protect plant tissues by helping to absorb the energy from
singlet oxygenSinglet oxygen is the common name used for the diamagnetic form of molecular oxygen , which is less stable than the normal triplet oxygen. Because of its unusual properties, singlet oxygen can persist for over an hour at room temperature, depending on the environment...
, an excited form of the oxygen molecule O
2 which is formed during photosynthesis.
β-Caroteneβ-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...
is composed of two
retinylRetinol 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....
groups, and is broken down in the mucosa of the human
small intestineThe small intestine is the part of the gastrointestinal tract following the stomach and followed by the large intestine, and is where much of the digestion and absorption of food takes place. In invertebrates such as worms, the terms "gastrointestinal tract" and "large intestine" are often used to...
by β-carotene 15,15'-monooxygenase to
retinalRetinal, 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...
, a form of
vitamin AVitamin 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...
. β-Carotene can be stored in the
liverThe liver is a vital organ present in vertebrates and some other animals. It has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion...
and body fat and converted to retinal as needed, thus making it a form of
vitamin AVitamin 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...
for humans and some other mammals. The carotenes α-carotene and γ-carotene, due to their single retinyl group (beta-
iononeThe 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...
ring), also have some vitamin A activity (though less than β-carotene), as does the
xanthophyllXanthophylls 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...
carotenoid β-
cryptoxanthinCryptoxanthin 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:...
. All other carotenoids, including
lycopeneLycopene 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...
, 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-
iononeThe 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...
) containing carotenoids to retinals. Carnivores in general are poor converters of dietary ionine-containg carotenoids. Pure carnivores such as ferets 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
Chemically, carotenes are polyunsaturated
hydrocarbonIn 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 containing 40 carbon atoms per molecule, variable numbers of hydrogen atoms, and no other elements. Some carotenes are terminated by hydrocarbon rings, on one or both ends of the molecule. All are coloured to the human eye, due to extensive systems of conjugated double bonds. Structurally carotenes are
tetraterpeneTetraterpenes are terpenes consisting of eight isoprene units and have the molecular formula C40H64.Biologically important tetraterpenes include the acyclic lycopene, the monocyclic gamma-carotene, and the bicyclic alpha- and beta-carotenes....
s, meaning that they are synthesized biochemically from four 10-carbon
terpeneTerpenes 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, which in turn are formed from eight 5-carbon
isopreneIsoprene , or 2-methyl-1,3-butadiene, is a common organic compound with the formula CH2=CCH=CH2. Under standard conditions it is a colorless liquid...
units.
Carotenes are found in plants in two primary forms designated by characters from the
Greek alphabetThe Greek alphabet is the script that has been used to write the Greek language since at least 730 BC . The alphabet in its classical and modern form consists of 24 letters ordered in sequence from alpha to omega...
:
alpha-caroteneα-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:...
(α-carotene) and
beta-caroteneβ-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...
(β-carotene). Gamma, delta, epsilon, and zeta (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 carotenoids, the
xanthophyllXanthophylls 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 thus are less chemically hydrophobic).
Dietary sources
The following foods are particularly rich in carotenes (also see
Vitamin AVitamin 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...
article for amounts):
- sweet potatoes
- carrots
- wolfberries (goji)
- cantaloupe melon
- mangoes
- apricots
- Persimmon
A persimmon is the edible fruit of a number of species of trees in the genus Diospyros in the ebony wood family . The word Diospyros means "the fire of Zeus" in ancient Greek. As a tree, it is a perennial plant...
- spinach
Spinach is an edible flowering plant in the family of Amaranthaceae. It is native to central and southwestern Asia. It is an annual plant , which grows to a height of up to 30 cm. Spinach may survive over winter in temperate regions...
- kale
Kale is very high in beta carotene, vitamin K, vitamin C, lutein, zeaxanthin, and reasonably rich in calcium. Kale, as with broccoli and other brassicas, contains sulforaphane , a chemical with potent anti-cancer properties. Boiling decreases the level of sulforaphane; however, steaming,...
- chard
Chard , is a leafy green vegetable often used in Mediterranean cooking. While the leaves are always green, chard stalks vary in color. Chard has been bred to have highly nutrious leaves at the expense of the root...
- turnip greens
- dandelion greens
- beet greens
- mustard greens
- collard greens
Collard greens are various loose-leafed cultivars of Brassica oleracea , the same species as cabbage and broccoli. The plant is grown for its large, dark-colored, edible leaves and as a garden ornamental, mainly in Brazil, Portugal, the southern United States, many parts of Africa, Montenegro,...
- watercress
Watercresses are fast-growing, aquatic or semi-aquatic, perennial plants native from Europe to central Asia, and one of the oldest known leaf vegetables consumed by human beings...
- cilantro
- fresh thyme
Thyme is a culinary and medicinal herb of the genus Thymus.-History:Ancient Egyptians used thyme for embalming. The ancient Greeks used it in their baths and burnt it as incense in their temples, believing it was a source of courage...
- broccoli
Broccoli is a plant in the cabbage family, whose large flower head is used as a vegetable.-General:The word broccoli, from the Italian plural of , refers to "the flowering top of a cabbage"....
- parsley
Parsley is a species of Petroselinum in the family Apiaceae, native to the central Mediterranean region , naturalized elsewhere in Europe, and widely cultivated as an herb, a spice and a vegetable.- Description :Garden parsley is a bright green hairless biennial herbaceous plant in temperate...
- romaine lettuce
Romaine or cos lettuce is a variety of lettuce which grows in a tall head of sturdy leaves with a firm rib down the center. Unlike most lettuces, it is tolerant of heat...
- ivy gourd
- rose hips
- winter squash
Winter squash is a summer-growing annual vegetable, representing several species within the genus Cucurbita. It differs from summer squash in that it is harvested and eaten in the mature fruit stage, when the seeds within have matured fully and the skin has hardened into a tough rind. At this...
- pumpkin
A pumpkin is a gourd-like squash of the genus Cucurbita and the family Cucurbitaceae . It commonly refers to cultivars of any one of the species Cucurbita pepo, Cucurbita mixta, Cucurbita maxima, and Cucurbita moschata, and is native to North America...
- cassava
Cassava , also called yuca or manioc, a woody shrub of the Euphorbiaceae native to South America, is extensively cultivated as an annual crop in tropical and subtropical regions for its edible starchy tuberous root, a major source of carbohydrates...
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 wallThe cell wall is the tough, usually flexible but sometimes fairly rigid layer that surrounds some types of cells. It is located outside the cell membrane and provides these cells with structural support and protection, and also acts as a filtering mechanism. A major function of the cell wall is to...
splits and the colour is released into any liquid. 6 μg of dietary β-carotene supplies the equivalent of 1 μg of retinol, or 1 RE (Retinol Equivalent). This is equivalent to 3⅓
IUIn pharmacology, the International Unit is a unit of measurement for the amount of a substance, based on biological activity or effect. It is abbreviated as IU, as UI , or as IE...
of vitamin A.
The multiple forms
The two primary
isomerIn chemistry, isomers are compounds with the same molecular formula but different structural formulas. Isomers do not necessarily share similar properties, unless they also have the same functional groups. There are many different classes of isomers, like stereoisomers, enantiomers, geometrical...
s of carotene, α-carotene and β-carotene, differ in the position of a
double bondA double bond in chemistry is a chemical bond between two chemical elements involving four bonding electrons instead of the usual two. The most common double bond, that between two carbon atoms, can be found in alkenes. Many types of double bonds between two different elements exist, for example in...
(and thus a hydrogen) in the cyclic group at one end (left in the diagram here).
β-Caroteneβ-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...
is the more common form and can be found in
yellowYellow is the color evoked by light that stimulates both the L and M cone cells of the retina about equally, with no significant stimulation of the S cone cells. Light with a wavelength of 570–590 nm is yellow, as is light with a suitable mixture of red and green...
,
orangeThe colour orange occurs between red and yellow in the visible spectrum at a wavelength of about 585–620 nm, and has a hue of 30° in HSV colour space. It is numerically halfway between red and yellow in a gamma-compressed RGB colour space, the expression of which is the RGB colour wheel. The...
, and
greenGreen is a color, the perception of which is evoked by light having a spectrum dominated by energy with a wavelength of roughly 520–570 nanometres. In the subtractive color system, it is not a primary color, but is created out of a mixture of yellow and blue, or yellow and cyan; it is considered...
leafy
fruitIn broad terms, a fruit is a structure of a plant that contains its seeds.The term has different meanings dependent on context. In non-technical usage, such as food preparation, fruit normally means the fleshy seed-associated structures of certain plants that are sweet and edible in the raw state,...
s and
vegetableThe noun vegetable usually means an edible plant or part of a plant other than a sweet fruit or seed. This typically means the leaf, stem, or root of a plant....
s. As a
rule of thumbA rule of thumb is a principle with broad application that is not intended to be strictly accurate or reliable for every situation. It is an easily learned and easily applied procedure for approximately calculating or recalling some value, or for making some determination...
, 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. β-Carotene is an anti-oxidant.
β-Carotene and cancer
It has been shown in trials that the ingestion of β-carotene at about 30 mg/day (10 times the
Reference Daily IntakeThe Reference Daily Intake or Recommended Daily Intake is the daily intake level of a nutrient that is considered to be sufficient to meet the requirements of 97–98% of healthy individuals in every demographic in the United States .The RDI is used to determine the Daily Value of foods,...
) increases the rate of lung cancer and prostate cancer in
smokerSmoker is a noun derived from "smoke"/"smoking" and may have the following specialized meanings:* Someone who smokes tobacco or cannabis, cigarette substitutes, or various other drugs* Smoking , smoker, an apparatus for smoking...
s and people with a history of
asbestosAsbestos is a set of six naturally occurring silicate minerals used commercially for their desirable physical properties. They all have in common their eponymous, asbestiform habit: long, thin fibrous crystals...
exposure.
An article on the
American Cancer SocietyThe American Cancer Society is the "nationwide community-based voluntary health organization" dedicated, in their own words, "to eliminating cancer as a major health problem by preventing cancer, saving lives, and diminishing suffering from cancer, through research, education, advocacy, and...
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 published an article in 1994 about a trial which examined the relationship between daily supplementation of β-carotene and
vitamin EVitamin E is used to refer to a group of fat-soluble compounds that include both tocopherols and tocotrienols. There are many different forms of vitamin E, of which γ-tocopherol is the most common in the North American diet. γ-Tocopherol can be found in corn oil, soybean oil, margarine and dressings...
(alpha-tocopherol) 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 InstituteThe National Cancer Institute is part of the National Institutes of Health , which is one of 11 agencies that are part of the U.S. Department of Health and Human Services. The NCI coordinates the U.S...
and The New England Journal of Medicine published articles in 1996 about a trial that was conducted to determine if vitamin A (in the form of retinyl palmitate) and β-carotene had any beneficial effects to prevent cancer. The results indicated an increased risk of lung cancer for the participants who consumed the β-carotene supplement and who had lung irritation from
smokingTobacco smoking is the practice where tobacco is burned and the resulting smoke is inhaled. The practice may have begun as early as 5000–3000 BCE. Tobacco was introduced to Eurasia in the late 16th century where it followed common trade routes...
or
asbestosAsbestos is a set of six naturally occurring silicate minerals used commercially for their desirable physical properties. They all have in common their eponymous, asbestiform habit: long, thin fibrous crystals...
exposure, causing the trial to be stopped early.
A review of all randomized controlled trials in the scientific literature by the
Cochrane CollaborationThe Cochrane Collaboration is a group of over 28,000 volunteers in more than 100 countries who review the effects of health care interventions tested in biomedical randomized controlled trials. A few more recent reviews have also studied the results of non-randomized, observational studies...
published in
JAMAThe Journal of the American Medical Association is a weekly, peer-reviewed, medical journal, published by the American Medical Association. Beginning in July 2011, the editor in chief will be Howard C. Bauchner, vice chairman of pediatrics at Boston University’s School of Medicine, replacing ...
in 2007 found that β-carotene
increased mortality by something between 1 and 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.
β-Carotene and cognition
A recent report demonstrated that 50 mg of β-carotene every other day prevented cognitive decline in a study of over 4000 physicians at a mean treatment duration of 18 years.
β-Carotene and photosensitivity
Oral β-carotene is prescribed to people suffering from
erythropoietic protoporphyriaErythropoietic protoporphyria is a relatively mild form of porphyria, although very painful, which arises from a deficiency in the enzyme ferrochelatase, leading to abnormally high levels of protoporphyrin in the tissue...
. It provides them some relief from photosensitivity.
β-Carotene and nanotechnology
β-Carotene and
lycopeneLycopene 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...
molecules can be encapsulated into carbon nanotubes enhancing the
optical properties of carbon nanotubesWithin materials science, the optical properties of carbon nanotubes refer specifically to the absorption, photoluminescence, and Raman spectroscopy of carbon nanotubes. Spectroscopic methods offer the possibility of quick and non-destructive characterization of relatively large amounts of carbon...
. Efficient energy transfer occurs between the encapsulated dye and nanotube — light is absorbed by the dye and without significant loss is transferred to the SWCNT. Encapsulation increases chemical and thermal stability of carotene molecules; it also allows their isolation and individual characterization.
α-carotene and risk of death
Higher dietary intake and blood serum levels of
alpha-caroteneα-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:...
are associated with significantly lower risk of death. (See
alpha-caroteneα-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:...
for details and refs.)
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
conjunctivaThe conjunctiva covers the sclera and lines the inside of the eyelids. It is composed of rare stratified columnar epithelium.-Function:...
of eyes (thus easily distinguishing it visually from
jaundiceJaundice is a yellowish pigmentation of the skin, the conjunctival membranes over the sclerae , and other mucous membranes caused by hyperbilirubinemia . This hyperbilirubinemia subsequently causes increased levels of bilirubin in the extracellular fluid...
). It is most commonly associated with consumption of an abundance of
carrotThe carrot is a root vegetable, usually orange in colour, though purple, red, white, and yellow varieties exist. It has a crisp texture when fresh...
s, but it also can be a
medical signA medical sign is an objective indication of some medical fact or characteristic that may be detected by a physician during a physical examination of a patient....
of more dangerous conditions.
Production
Most of the world's synthetic supply of carotene comes from a manufacturing complex located in
Freeport, TexasFreeport is a city in Brazoria County, Texas within the Houston–Sugar Land–Baytown metropolitan area and is situated in Southeast Texas. As of the 2000 U.S...
and owned by
DSMDSM is a multinational life sciences and materials sciences-based company. DSM's global end markets include food and dietary supplements, personal care, feed, pharmaceuticals, medical devices, automotive, paints, electrical and electronics, life protection, alternative energy and bio-based materials...
. The other major supplier
BASFBASF SE is the largest chemical company in the world and is headquartered in Germany. BASF originally stood for Badische Anilin- und Soda-Fabrik . Today, the four letters are a registered trademark and the company is listed on the Frankfurt Stock Exchange, London Stock Exchange, and Zurich Stock...
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 trisporaBlakeslea trispora is a fungal plant pathogen of the genus Blakeslea.It is also a source of commercial beta carotene for dietary supplements and food additives.- External links :**...
, 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 salinaDunaliella salina is a type of halophile green micro-algae especially found in sea salt fields. Known for its anti-oxidant activity because of its ability to create large amount of carotenoids, it is used in cosmetics and dietary supplements. Few organisms can survive in such highly saline...
grown in harvesting ponds situated in
Karratha, Western Australia-Facilities:A range of hotel, motel, B&B and caravan/RV accommodation is available for visitors. However, as the town is booming, accommodation is often hard to come by.The town has restaurants, a tavern, two hotels and two night clubs...
. Cognis Australia Pty. Ltd., a subsidiary of the Germany-based company
CognisCognis is a worldwide supplier of specialty chemicals and nutritional ingredients, headquartered in Monheim am Rhein, Germany. The company employs about 5,600 people and operates production or service centers in almost 30 countries....
, is also producing β-carotene from microalgae grown in two sites in Australia that are the world’s largest algae farms. In
PortugalPortugal , officially the Portuguese Republic is a country situated in southwestern Europe on the Iberian Peninsula. Portugal is the westernmost country of Europe, and is bordered by the Atlantic Ocean to the West and South and by Spain to the North and East. The Atlantic archipelagos of the...
, the
industrial biotechnologyIndustrial biotechnology is the application of biotechnology for industrial purposes, including manufacturing, alternative energy , and biomaterials. It includes the practice of using cells or components of cells like enzymes to generate industrially useful products...
company Biotrend is producing natural all-
trans-β-carotene from a non genetically modified bacteria of the
SphingomonasSphingomonas was defined in 1990 as a group of Gram-negative, rod-shaped, chemoheterotrophic, strictly aerobic bacteria. They possess ubiquinone 10 as their major respiratory quinone, contain glycosphingolipids instead of lipopolysaccharide in their cell envelopes, and typically produce...
genus isolated from soil.
Carotenes are also found in palm oil, 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
GuernseyGuernsey, officially the Bailiwick of Guernsey is a British Crown dependency in the English Channel off the coast of Normandy.The Bailiwick, as a governing entity, embraces not only all 10 parishes on the Island of Guernsey, but also the islands of Herm, Jethou, Burhou, and Lihou and their islet...
cows, tend to be more yellow 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.
Total synthesis
There are currently two commonly used methods of
total synthesisIn organic chemistry, a total synthesis is, in principle, the complete chemical synthesis of complex organic molecules from simpler pieces, usually without the aid of biological processes. In practice, these simpler pieces are commercially available in bulk and semi-bulk quantities, and are often...
of β-carotene. The first was developed by the Badische Anilin- & Soda-Fabrik (
BASFBASF SE is the largest chemical company in the world and is headquartered in Germany. BASF originally stood for Badische Anilin- und Soda-Fabrik . Today, the four letters are a registered trademark and the company is listed on the Frankfurt Stock Exchange, London Stock Exchange, and Zurich Stock...
) and is based on the
Wittig reactionThe Wittig reaction is a chemical reaction of an aldehyde or ketone with a triphenyl phosphonium ylide to give an alkene and triphenylphosphine oxide....
with Wittig himself as patent holder:
The second is a
Grignard reactionThe Grignard reaction is an organometallic chemical reaction in which alkyl- or aryl-magnesium halides add to a carbonyl group in an aldehyde or ketone. This reaction is an important tool for the formation of carbon–carbon bonds...
, elaborated by Hoffman-La Roche 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 carotenoids containing no oxygen. Carotenoids containing some oxygen are known as
xanthophyllXanthophylls 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 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 is the 23rd letter of the Greek alphabet and has a numeric value of 700. In both Classical and Modern Greek, the letter indicates the combination /ps/ . The letter was adopted into the Old Italic alphabet, and its shape is continued into the Algiz rune of the Elder Futhark...
) is β,ψ-carotene;
- δ-carotene (with one ε ring and one uncyclized end) is ε,ψ-carotene;
- ε-carotene is ε,ε-carotene
- 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...
is ψ,ψ-carotene
ζ-carotene is the
biosyntheticBiosynthesis is an enzyme-catalyzed process in cells of living organisms by which substrates are converted to more complex products. The biosynthesis process often consists of several enzymatic steps in which the product of one step is used as substrate in the following step...
precursorIn chemistry, a precursor is a compound that participates in the chemical reaction that produces another compound. In biochemistry, the term "precursor" is used more specifically to refer to a chemical compound preceding another in a metabolic pathway....
of neurosporene, which is the precursor of lycopene, which, in turn, is the precursor of the carotenes α through ε.
Food additive
Carotene is also used as a substance 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 USA.
External links