Carotenoid

The orange ring surrounding Grand Prismatic Spring is due to carotenoid molecules, produced by huge mats of algae and bacteria.

Carotenoid is any of a large class of over 600 organic pigments, including the carotenes and xanthophylls, that are widely distributed in nature and typically impart yellow, orange, red, or purple colors. Generally they are fat-soluble, dissolving in fats and oils but not water, except when complexed with proteins. In plants, they naturally occur in chromoplasts , imparting color to fruits and vegetables, such as carrots, pumpkins, sweet potatoes, and tomatoes. They also are found in some other photosynthetic organisms like algae, some types of fungus, and some bacteria.

In animals such as crustaceans, nudibranches, and echinoderms, carotenoprotein complexes give red, purple, green, blue, and other colors. Animals obtain it through the diet. For example, the pink colour of flamingos and salmon, and the red colouring of lobsters are due to carotenoids.

Carotenoids serve two key roles in plants and algae: they absorb light energy for use in photosynthesis, and they protect chlorophyll from photodamage (Armstrong and Hearst 1996). In humans, carotenoids such as beta-carotene are a precursor to vitamin A, a pigment essential for good vision, and carotenoids can also act as antioxidants (Sims and Odle 2005).

protect cells from damage from energy of the sun... protect stems and leaves. limit free radical damage In humans, act as antioxidants to protect scells form damage of free radicals produced by metabolism, cigarettee smoke, sunlihght, radiation, pollutants,or stress.

example: deciduous trees

Overview and properties

Carotenoids are a type of terpenoid (sometimes referred to as isoprenoids), which are hydrocarbons resulting from the combination of several five-carbon isoprene units. Specifically, they are tetraterpenoids, which means they are derived from 8 isoprene units—meaning they typically contain 40 carbon atoms. Structurally they are in the form of a polyene chain that is sometimes terminated by rings. 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.

• General strucutre is aliphatic and aliphatic-alicyclic polyenes, with a few aromatic-type polyenes

They absorb blue light. 

they are split into two smaller classes of pigments, xanthophylls and carotenes.

• Carotenoids with molecules containing oxygen, such as lutein and zeaxanthin, are known as xanthophylls.

• The unoxygenated (oxygen free) carotenoids such as alpha-carotene, beta-carotene and lycopene are known as carotenes. Carotenes typically contain only carbon and hydrogen.

Important carotenes include beta-caotene, lycopene, and alpha-carotene. Important xanthophylls include lutein, zeaxanthin, cryptoxanthin, and astaxanthin.

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, 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.^{[citation needed]}

Probably the most well-known carotenoid is the one that gives this second group its name, carotene, found in carrots (also apricots) and responsible for their bright orange colour. Crude palm oil, however, is the richest source of carotenoids in nature.

Briefly describe beta-carotene, etc.

The most common carotenoids include lycopene and the vitamin A precursor β-carotene. In plants, the xanthophyll lutein 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 leaves are not obvious because of the presence of other pigments such as chlorophyll.

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.

Biochemical functions and importance

overall statement: photosynthesis, protection

In photosynthetic organisms, 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, carotenoids have been linked to oxidation-preventing mechanisms.

File:Carotenoids disposition in proteins.png

Carotenoids disposition in proteins. Left: in cyanobacterium photosystem I carotenoids are outside (orange) PDB 1jb0. Right: in rhodopsin retinal is deep inside (pink) PDB 1f88.

Carotenoids have many physiological functions. Given their structure (above), carotenoids are efficient free-radical scavengers, and they enhance the vertebrate immune system.

Animals are incapable of synthesizing carotenoids, and must obtain them through their diet, yet they are common and often in ornamental features. It has been proposed that carotenoids are used in ornamental traits 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.

File:Carotenoid.PNG

Simplified carotenoid synthesis pathway.

Despite being important in nutrition, some carotenoids are produced by bacteria to protect themselves from immune attack, such as MRSA. The golden pigment of S. aureus allows it to survive competitive attack by Lactobaccillus as well as the human immune system.

Human health and carotenoids

free radicals Consequently, epidemiological studies have shown that people with high beta-carotene intake and high plasma levels of beta-carotene have a significantly reduced risk of lung cancer. However, studies of supplementation with large doses of beta-carotene in smokers have shown an increase in cancer risk (possibly because excessive beta-carotene results in breakdown products that reduce plasma vitamin A and worsen the lung cell proliferation induced by smoke). Similar results have been found in other animals. Not all carotenoids are helpful, e.g. etretinate is a teratogen.

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.^{[citation needed]} However, a recent meta-analysis of 68 reliable antioxidant supplementation experiments involving a total of 232,606 individuals concluded that consuming additional beta-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. Since most carotenoid-rich fruits and vegetables are low in lipids and 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 (alpha-carotene, beta-carotene, lycopene, and lutein).

Aroma chemicals

Products of carotenoid degradation such as ionones, damascones, and damascenones are also important fragrance chemicals that are used extensively in the perfumes and fragrance industry. Both beta-damascenone and beta-ionone although low in concentration in rose distillates are the key odour-contributing compounds in flowers. In fact, the sweet floral smells present in black tea, aged tobacco, grape, and many fruits are due to the aromatic compounds resulting from carotenoid breakdown.

List of Naturally occurring carotenoids

• Hydrocarbons

• • Lycopersene 7,8,11,12,15,7',8',11',12',15'-Decahydro-y,y-carotene
  • Phytofluene
  • Hexahydrolycopene 15-cis-7,8,11,12,7',8'-Hexahydro-y,y-carotene
  • Torulene 3',4'-Didehydro-b,y-carotene
  • a-Zeacarotene 7',8'-Dihydro-e,y-carotene

• Alcohols

• • Alloxanthin
  • Cynthiaxanthin
  • Pectenoxanthin
  • Cryptomonaxanthin (3R,3'R)-7,8,7',8'-Tetradehydro-b,b-carotene-3,3'-diol
  • Crustaxanthin b,b-Carotene-3,4,3',4'-tetrol
  • Gazaniaxanthin (3R)-5'-cis-b,y-Caroten-3-ol
  • OH-Chlorobactene 1',2'-Dihydro-f,y-caroten-1'-ol
  • Loroxanthin b,e-Carotene-3,19,3'-triol
  • Lycoxanthin y,y-Caroten-16-ol
  • Rhodopin 1,2-Dihydro-y,y-caroten-l-ol
  • Rhodopinol aka Warmingol 13-cis-1,2-Dihydro-y,y-carotene-1,20-diol
  • Saproxanthin 3',4'-Didehydro-1',2'-dihydro-b,y-carotene-3,1'-diol

• Glycosides

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

• Ethers

• • Rhodovibrin 1'-Methoxy-3',4'-didehydro-1,2,1',2'-tetrahydro-y,y-caroten-1-ol
  • Spheroidene 1-Methoxy-3,4-didehydro-1,2,7',8'-tetrahydro-y,y-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-b,b-carotene-3,3'-diol
  • Mutatoxanthin
  • Citroxanthin
  • Zeaxanthin furanoxide 5,8-Epoxy-5,8-dihydro-b,b-carotene-3,3'-diol
  • Neochrome 5',8'-Epoxy-6,7-didehydro-5,6,5',8'-tetrahydro-b,b-carotene-3,5,3'-triol
  • Foliachrome
  • Trollichrome
  • Vaucheriaxanthin 5',6'-Epoxy-6,7-didehydro-5,6,5',6'-tetrahydro-b,b-carotene-3,5,19,3'-tetrol

• Aldehydes

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

• Acids and Acid Esters

• • Torularhodin 3',4'-Didehydro-b,y-caroten-16'-oic acid
  • Torularhodin methyl ester Methyl 3',4'-didehydro-b,y-caroten-16'-oate

• Ketones

• • Canthaxanthin aka Aphanicin, Chlorellaxanthin b,b-Carotene-4,4'-dione
  • Capsanthin (3R,3'S,5'R)-3,3'-Dihydroxy-b,k-caroten-6'-one
  • Capsorubin (3S,5R,3'S,5'R)-3,3'-Dihydroxy-k,k-carotene-6,6'-dione
  • Cryptocapsin (3'R,5'R)-3'-Hydroxy-b,k-caroten-6'-one

2,2'-Diketospirilloxanthin 1,1'-Dimethoxy-3,4,3',4'-tetradehydro-1,2,1',2'-tetrahydro-y,y-carotene-2,2'-dione

• • Flexixanthin 3,1'-Dihydroxy-3',4'-didehydro-1',2'-dihydro-b,y-caroten-4-one
  • 3-OH-Canthaxanthin aka Adonirubin aka Phoenicoxanthin 3-Hydroxy-b,b-carotene-4,4'-dione
  • Hydroxyspheriodenone 1'-Hydroxy-1-methoxy-3,4-didehydro-1,2,1',2',7',8'-hexahydro-y,y-caroten-2-one
  • Okenone 1'-Methoxy-1',2'-dihydro-c,y-caroten-4'-one
  • Pectenolone 3,3'-Dihydroxy-7',8'-didehydro-b,b-caroten-4-one
  • Phoeniconone aka Dehydroadonirubin 3-Hydroxy-2,3-didehydro-b,b-carotene-4,4'-dione
  • Phoenicopterone b,e-caroten-4-one
  • Rubixanthone 3-Hydroxy-b,y-caroten-4'-one
  • Siphonaxanthin 3,19,3'-Trihydroxy-7,8-dihydro-b,e-caroten-8-one

• Esters of Alcohols

• • Astacein 3,3'-Bispalmitoyloxy-2,3,2',3'-tetradehydro-b,b-carotene-4,4'-dione or
• 3,3'-dihydroxy-2,3,2',3'-tetradehydro-b,b-carotene-4,4'-dione dipalmitate
  • Fucoxanthin 3'-Acetoxy-5,6-epoxy-3,5'-dihydroxy-6',7'-didehydro-5,6,7,8,5',6'-hexahydro-b,b-caroten-8-one
  • Isofucoxanthin 3'-Acetoxy-3,5,5'-trihydroxy-6',7'-didehydro-5,8,5',6'-tetrahydro-b,b-caroten-8-one
  • Physalien
  • Zeaxanthin dipalmitate (3R,3'R)-3,3'-Bispalmitoyloxy-b,b-carotene or

(3R,3'R)-b,b-carotene-3,3'-diol dipalmitate

• • Siphonein 3,3'-Dihydroxy-19-lauroyloxy-7,8-dihydro-b,e-caroten-8-one or

3,19,3'-trihydroxy-7,8-dihydro-b,e-caroten-8-one 19-laurate

• Apo Carotenoids

• • b-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-b-caroten-10'-al
  • Bixin 6'-Methyl hydrogen 9'-cis-6,6'-diapocarotene-6,6'-dioate
  • Citranaxanthin 5',6'-Dihydro-5'-apo-b-caroten-6'-one or

5',6'-dihydro-5'-apo-18'-nor-b-caroten-6'-one or 6'-methyl-6'-apo-b-caroten-6'-one

• • Crocetin 8,8'-Diapo-8,8'-carotenedioic acid
  • Crocetinsemialdehyde 8'-Oxo-8,8'-diapo-8-carotenoic acid
  • Crocin 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
  • b-Carotenone 5,6:5',6'-Diseco-b,b-carotene-5,6,5',6'-tetrone
  • Peridinin 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-a-carotenone 5,6-Seco-b,e-carotene-5,6-dione
  • Semi-b-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 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

References

ISBN links support NWE through referral fees

.

• McGraw-Hill Concise Encyclopedia of Science & Technology, 5th edition. 2005. New York: McGraw-Hill. ISBN 0071429573.

• Sims, J., and T. G. Odle. 2005. Carotenoids. In J. L. Longe, The Gale Encyclopedia of Alternative Medicine, Farmington Hills, Mich: Thomson/Gale, ISBN 0787693960

External links

• http://www.carotenoidsociety.org/
• Carotenoid Terpenoids
• Carotenoids as Flavor and Fragrance Precursors
• MeSH Carotenoids

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