Carotenoids

thumb|upright=1.4|A 3-dimensional stick diagram of β-carotene thumb|Carotene is responsible for the orange colour of carrots and the colours of many other fruits and vegetables and even some animals. thumb|Lesser flamingo|Lesser flamingos in the [[Ngorongoro Crater, Tanzania. The pink colour of wild flamingos is due to astaxanthin (a carotenoid) they absorb from their diet of brine shrimp. If fed a carotene-free diet they become white.]]

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 vegetables.

thumb|class=skin-invert-image|Chemical structure of β-carotene, a common natural pigment|420px

β-Carotene (beta-carotene) is an organic, strongly colored red-orange pigment abundant in fungi, plants, and fruits. It is a member of the carotenes, which are terpenoids (isoprenoids), synthesized biochemically from eight isoprene units and thus having 40 carbons.

Lutein (; from Latin luteus meaning "yellow") 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, kale and yellow carrots. In green plants, xanthophylls act to modulate light energy and serve as non-photochemical quenching agents to deal with triplet chlorophyll, an excited form of chlorophyll which is overproduced at high light levels during photosynthesis.

thumb|The characteristic color of egg yolk results from the presence of a xanthophyll pigment typical in color of lutein or zeaxanthin of the xanthophylls, a division of the carotenoids group. 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", and (), meaning "leaf"), due to their formation of the yellow band seen in early chromatography of leaf pigments.

Astaxanthin is a keto-carotenoid within a group of chemical compounds known as carotenoids, a subclass of the broad group of phytochemicals known as terpenes. Astaxanthin is a metabolite of zeaxanthin and canthaxanthin, containing both hydroxyl and ketone functional groups.

Zeaxanthin is one of the most common carotenoids in nature, and is used in the xanthophyll cycle. Synthesized in plants and some micro-organisms, it is the pigment that gives paprika (made from red sweet peppers), corn, saffron, goji (wolfberries), and many other plants and microbes their characteristic color.

Tretinoin, also known as 'all-trans retinoic acid (ATRA'), is a medication used for the treatment of acne and acute promyelocytic leukemia. For acne, it is applied to the skin as a cream, gel or ointment. For acute promyelocytic leukemia, it is effective only when the RARA-PML fusion mutation is present and is taken by mouth for up to three months. Topical tretinoin is also the most extensively investigated retinoid therapy for photoaging.

thumb|Red, blue, and purple colors of berries derive mainly from polyphenol phytochemicals called [[anthocyanins.]] thumb|Cucurbita fruits, including squash and [[pumpkin, typically have high content of the phytochemical pigments called carotenoids.]]

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. Fucoxanthin absorbs light primarily in the blue-green to yellow-green part of the visible spectrum, peaking at around 510–525 nm and absorbing significantly in the range of 450 to 540 nm.

species of bird

Canthaxanthin is a keto-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 was first isolated in edible mushrooms. It has also been found in green algae, bacteria, crustaceans, and bioaccumulates in fish such as carp, golden grey mullet, seabream and trush wrasse.

β-Cryptoxanthin is a natural carotenoid pigment. It has been isolated from a variety of sources including the fruit of plants in the genus Physalis, orange rind, winter squashes such as butternut, papaya, egg yolk, butter, apples, and bovine blood serum.

α-Carotene (alpha-carotene) is a form of carotene with a β-ionone ring at one end and an α-ionone ring at the opposite end. It is the second most common form of carotene.

Violaxanthin is a xanthophyll pigment with an orange color found in a variety of plants. Violaxanthin is the product of the epoxidation of zeaxanthin where the oxygen atoms are from reactive oxygen species (ROS). Such ROS's arise when a plant is subject to solar radiation so intense that the light cannot all be absorbed by the chlorophyll.

Rhodoxanthin is a xanthophyll pigment with a purple color that is found in small quantities in a variety of plants including Taxus baccata and Lonicera morrowii. It is also found in the feathers of some birds. As a food additive it is used under the E number E161f as a food coloring. It is not approved for use in the EU or US; however, it is approved in Australia and New Zealand (where it is listed under its INS number 161f).

Flavoxanthin is a natural xanthophyll pigment with a golden-yellow color found in small quantities in a variety of plants. As a food additive it used under the E number E161a as a food coloring although it is not approved for use in the EU or USA. It is listed as food additive 161a in Australia and New Zealand where it is approved for usage as an ingredient in food products.

Rubixanthin, or natural yellow 27, is a natural xanthophyll pigment with a red-orange color found in rose hips. As a food additive it used under the E number E161d as a food coloring; it is not approved for use in the USA or EU but is approved in Australia and New Zealand where it is listed as 161d.

Phytoene () is a 40-carbon intermediate in the biosynthesis of carotenoids. The synthesis of phytoene is the first committed step in the synthesis of carotenoids in plants. Phytoene is produced from two molecules of geranylgeranyl pyrophosphate (GGPP) by the action of the enzyme phytoene synthase. The two GGPP molecules are condensed together followed by removal of diphosphate and proton shift leading to the formation of phytoene.

γ-Carotene (gamma-carotene) is a carotenoid, and is a biosynthetic intermediate for cyclized carotenoid synthesis in plants. It is formed from cyclization of lycopene by lycopene cyclase epsilon. Along with several other carotenoids, γ-carotene is a vitamer of vitamin A in herbivores and omnivores. Carotenoids with a cyclized, beta-ionone ring can be converted to vitamin A, also known as retinol, by the enzyme beta-carotene 15,15'-dioxygenase; however, the bioconversion of γ-carotene to retinol has not been well-characterized. γ-Carotene has tentatively been identified as a biomarker for green

thumbnail|left|all-trans Neoxanthin Neoxanthin is a carotenoid and xanthophyll. In plants, it is an intermediate in the biosynthesis of the plant hormone abscisic acid. It is often present in two forms: all-trans and 9-cis isomers. It is produced from violaxanthin, but a suspected neoxanthin synthase is still to be confirmed. Two different genes were confirmed to be implied in violaxanthin conversion to neoxanthin in Arabidopsis and tomato. It has a specific role in protection against photooxidative stress. It is a major xanthophyll found in green leafy vegetables such as spinach.

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.

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. beta-Damascenone is a major contributor to the aroma of roses, despite its very low concentration, and is an important fragrance chemical used in perfumery. Its aroma is described as "apple, rose, honey, tobacco, sweet".

δ-Carotene (delta-carotene) or ε,ψ-carotene is a form of carotene with an ε-ring at one end, and the other uncyclized, labelled ψ (psi). It is an intermediate synthesis product in some photosynthetic plants between lycopene and α-carotene (β,ε-carotene) or ε-carotene (ε,ε-carotene). δ-Carotene is fat soluble. Delta-carotene contains an alpha-ionone instead of a beta-ionone ring; this conversion is carried out by the gene Del which shifts the position of the double bond in the ring structure. The formation delta-carotene under the presence of the Del gene is sensitive to high temperatures.

Torulene (3',4'-didehydro-β,γ-carotene) is a carotene (a hydrocarbon carotenoid) which is notable for being synthesized by red pea aphids (Acyrthosiphon pisum), imparting the natural red color to the aphids, which aids in their camouflage and escape from predation. The aphids have gained the ability to synthesize torulene by horizontal gene transfer of a number of genes for carotenoid synthesis, apparently from fungi. Plants, fungi, and microorganisms can synthesize carotenoids, but torulene made by pea aphids is the only carotenoid known to be synthesized by an organism in the animal kingdom

Neurosporene is a carotenoid pigment. It is an intermediate in the biosynthesis of lycopene and a variety of bacterial carotenoids.

Phytofluene is a colorless carotenoid 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. In the following step, addition of carbon-carbon conjugated double bonds leads to the formation of z-carotene and appearance of visible color.

ζ-Carotene (zeta-carotene) is a carotenoid. It is different from α-carotene and β-carotene because it is acyclic. ζ-Carotene is similar in structure to lycopene, but has an additional 4 hydrogen atoms. ζ-carotene can be used as an intermediate in forming β-carotene. A dehydrogenation reaction converts ζ-carotene into lycopene, which then can be transformed into β-carotene through the action of lycopene beta-cyclase. ζ-Carotene is a natural product found in Lonicera japonica and Rhodospirillum rubrum.

Antheraxanthin (from ánthos, Greek for "flower" and xanthos, Greek for "yellow") is a bright yellow accessory pigment found in many organisms that perform photosynthesis. It is a xanthophyll cycle pigment, an oil-soluble alcohol within the xanthophyll subgroup of carotenoids. Antheraxanthin is both a component in and product of the cellular photoprotection mechanisms in photosynthetic green algae, red algae, euglenoids, and plants.

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. beta-Damascone is a contributor to the aroma of roses, despite its relatively low concentration, and is an important fragrance chemical used in perfumery.

Capsanthin is a natural red dye of the xanthophyll class of carotenoids. As a food coloring, it has the E number E160c(i). Capsanthin is the main carotenoid in the Capsicum annuum species of plants including red bell pepper, New Mexico chile, and cayenne peppers (Capsicum annuum) and a component of paprika oleoresin. Capsanthin is also found in some species of lily. Of all carotenoids, capsanthin is considered to have the greatest antioxidant capacity due to the presence of eleven conjugated double bonds, a conjugated keto group, and a cyclopentane ring.

ε-Carotene (epsilon-carotene) is a carotene. It can be synthesized from 2,7-dimethyl-2,4,6-octatrienedial and 2-methyl-4-(2,6,6-trimethyl-2-cyclohexen-1-yl)-3-butenal.

thumb|Diatoms, such as the diatom pictured here [[Phaeodactylum tricornutum, often contain diadinoxanthin pigments.]] Diadinoxanthin is a pigment found in phytoplankton. It has the formula C40H54O3. It gives rise to the xanthophylls diatoxanthin and dinoxanthin.

Staphyloxanthin is a carotenoid pigment that is produced by some strains of Staphylococcus aureus, and is responsible for the characteristic golden color that gives S. aureus its species name. Staphyloxanthin also 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. left|thumb|250x250px|The pigment staphyloxanthin gave the bacteria [[Staphylococcus aureus a yellow color.]] When comparing a normal strain of S. aureus with a strain modified to lack staphyloxanthin, the wildtype pigmented strain

Xanthoxin is an intermediate in the biosynthesis of the plant hormone abscisic acid.

Isorenieratene /ˌaɪsoʊrəˈnɪərətiːn/ is a carotenoid light-harvesting pigment produced exclusively by the genus Chlorobium, which are the brown-colored strains of the family of green sulfur bacteria (Chlorobiaceae). Green sulfur bacteria are anaerobic photoautotrophic organisms, meaning they perform photosynthesis in the absence of oxygen using hydrogen sulfide in the following reaction:

Diatoxanthin is a type of xanthophyll found in phytoplankton and diatoms. It is a naturally occurring -yne (alkyne).

Capsorubin is a natural red dye of the xanthophyll class. As a food coloring, it has the E number E160c(ii). Capsorubin is a carotenoid found in red bell pepper (Capsicum annuum) and a component of paprika oleoresin. Capsorubin is also found in some species of lily.

Dinoxanthin is a type of xanthophyll found in dinoflagellates. This compound is a potential antioxidant and may help to protect dinoflagellates against reactive oxygen species.

chemical compound