Editing Carotene

{{Short description|Class of compounds}}
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{{Distinguish|Keratin}}
{{For|the Canadian racehorse|Carotene (horse)}}
[[File:BetaCarotene-3d.png|thumb|upright=1.4|A 3-dimensional stick diagram of [[β-carotene]]]]
[[File:CarrotDiversityLg.jpg|thumb|Carotene is responsible for the orange colour of [[carrot]]s and the colours of many other fruits and vegetables and even some animals.]]
[[File:Lesser-flamingos.jpg|thumb|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.]]

The term '''carotene''' (also '''carotin''', from the Latin ''carota'', "carrot"<ref>Mosby's Medical, Nursing and Allied Health Dictionary, Fourth Edition, Mosby-Year Book 1994, p. 273</ref><ref name=OnlineEtDict>{{cite dictionary|title=carotene|url=http://www.etymonline.com/index.php?term=carotene&allowed_in_frame=0|dictionary=[[Online Etymology Dictionary]]}}</ref>) is used for many related [[unsaturated hydrocarbon]] substances having the formula C<sub>40</sub>H<sub>x</sub>, which are synthesized by plants but in general cannot be made by animals (with the exception of some [[aphid]]s and [[spider mite]]s which acquired the synthesizing genes from fungi).<ref name=KO>{{cite book |doi=10.1002/0471238961.0315121513011813.a01.pub3|chapter=Colorants for Foods, Drugs, and Cosmetics |title=Kirk-Othmer Encyclopedia of Chemical Technology |year=2012 |last1=Marmion |first1=Daniel |last2=Updated By Staff |isbn=978-0471238966 }}</ref> Carotenes are [[photosynthetic pigment]]s important for [[photosynthesis]].

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]], after which this class of chemicals is named, and for the colours of many other fruits, vegetables and fungi (for example, [[sweet potato]]es, [[chanterelle]] and orange [[cantaloupe]] 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]] to colourless retinoids, such as humans and [[chicken]]s, have yellow-coloured [[adipose tissue|body fat]], 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]]. They also protect plant tissues by helping to absorb the energy from [[singlet oxygen]], an excited form of the oxygen molecule O<sub>2</sub> which is formed during photosynthesis.

[[Beta-Carotene|β-Carotene]] is composed of two [[retinol|retinyl]] groups, and is broken down in the [[mucosa]] of the human [[small intestine]] by [[β-carotene 15,15'-monooxygenase]] to [[retinal]], a form of [[vitamin A]]. β-Carotene can be stored in the [[liver]] 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 [[alpha-Carotene|α-carotene]] and [[gamma-Carotene|γ-carotene]], due to their single retinyl group (β-[[ionone]] ring), also have some vitamin A activity (though less than β-carotene), as does the [[xanthophyll]] carotenoid β-[[cryptoxanthin]]. All other carotenoids, including [[lycopene]], 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-[[ionone]]) containing carotenoids to retinals. Carnivores in general are poor converters of dietary ionone-containing carotenoids. Pure carnivores such as [[ferret]]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.<ref>{{cite journal |vauthors=Green AS, Tang G, Lango J, Klasing KC, Fascetti AJ |title=Domestic cats convert ((2) H(8))-β-carotene to ((2) H(4))-retinol following a single oral dose |journal=Journal of Animal Physiology and Animal Nutrition |year=2011 |pmid=21797934 |doi=10.1111/j.1439-0396.2011.01196.x |pages=681–92 |volume=96 |issue=4}}</ref>

==Molecular structure==
Carotenes are polyunsaturated [[hydrocarbon]]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]]s. Carotenes are [[tetraterpene]]s, meaning that they are derived from eight 5-carbon [[isoprene]] units (or four 10-carbon terpene units).

Carotenes are found in plants in two primary forms designated by characters from the [[Greek alphabet]]: [[alpha-Carotene|alpha-carotene]] (α-carotene) and [[beta-Carotene|beta-carotene]] (β-carotene). [[gamma-Carotene|Gamma-]], [[delta-Carotene|delta-]], [[epsilon-Carotene|epsilon-]], and [[zeta-Carotene|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]]s, the [[xanthophyll]]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]] recognised its hydrocarbon nature in 1847, but his analyses gave him a composition of C<sub>5</sub>H<sub>8</sub>. It was [[Léon-Albert Arnaud]] in 1886 who confirmed its hydrocarbon nature and gave the formula C<sub>26</sub>H<sub>38</sub>, which is close to the theoretical composition of C<sub>40</sub>H<sub>56</sub>. [[Adolf Lieben]] in studies, also published in 1886, of the colouring matter in [[corpora lutea]], first came across carotenoids in animal tissue, but did not recognise the nature of the pigment. [[Johann Ludwig Wilhelm Thudichum]], in 1868–1869, after stereoscopic spectral examination, applied the term 'luteine' ([[lutein]]) to this class of yellow crystallizable substances found in animals and plants. [[Richard Martin Willstätter]], who gained the [[Nobel Prize]] in [[Chemistry]] in 1915, mainly for his work on [[chlorophyll]], assigned the composition of C<sub>40</sub>H<sub>56</sub>, distinguishing it from the similar but oxygenated [[xanthophyll]], C<sub>40</sub>H<sub>56</sub>O<sub>2</sub>. With Heinrich Escher, in 1910, [[lycopene]] was isolated from tomatoes and shown to be an [[isomer]] of carotene. Later work by Escher also differentiated the '[[luteal]]' pigments in egg yolk from that of the carotenes in cow corpus luteum.<ref>Theodore L. Sourkes, "The Discovery and Early History of Carotene," http://acshist.scs.illinois.edu/bulletin_open_access/v34-1/v34-1%20p32-38.pdf</ref>

==Dietary sources==
The following foods contain carotenes in notable amounts:<ref name=lpi>{{cite web | publisher = Micronutrient Information Center, Linus Pauling Institute, Oregon State University | title = Carotenoids| url = http://lpi.oregonstate.edu/infocenter/phytochemicals/carotenoids/
|date= 1 August 2016 | access-date = 19 August 2019}}</ref>
{{Div col|colwidth=18vw|gap=2vw}}
*[[carrot]]s<ref name=lpi/>
*[[Wolfberry|wolfberries]] (goji)<ref>{{cite journal |vauthors=Ajila CM, Prasada Rao UJ |title=Determination of carotenoids and their esters in fruits of ''Lycium barbarum'' Linnaeus by HPLC-DAD-APCI-MS |journal=J Pharm Biomed Anal |volume=47 |issue=4–5 |pages=812–8 |year=2008 |pmid=18486400 |doi=10.1016/j.jpba.2008.04.001}}</ref>
*[[cantaloupe]]<ref name="ods">{{cite web
  | title =Vitamin A: Fact Sheet for Health Professionals 
  | publisher = Office of Dietary Supplements, US National Institutes of Health
  | date =9 July 2019
  | url =https://ods.od.nih.gov/factsheets/Vitamina-HealthProfessional/
  | access-date = 19 August 2019}}</ref>
*[[mango]]es<ref name=lpi/>
*[[bell pepper|red bell pepper]]<ref name=lpi/> 
*[[papaya]]<ref name=lpi/><ref name="Schweig">{{cite journal | last1=Schweiggert | first1=Ralf M. | last2=Kopec | first2=Rachel E. | last3=Villalobos-Gutierrez | first3=Maria G. | last4=Högel | first4=Josef | last5=Quesada | first5=Silvia | last6=Esquivel | first6=Patricia | last7=Schwartz | first7=Steven J. | last8=Carle | first8=Reinhold | title=Carotenoids are more bioavailable from papaya than from tomato and carrot in humans: a randomised cross-over study | journal=British Journal of Nutrition | volume=111 | issue=3 | date=2013-08-12 | issn=0007-1145 | doi=10.1017/s0007114513002596 | pages=490–498|pmid=23931131|pmc=4091614 }}</ref>
*[[spinach]]<ref name=lpi/>
*[[kale]]<ref name=lpi/>
*[[sweet potato]]<ref name=lpi/>
*[[tomato]]<ref name=lpi/>
*[[dandelion greens]]<ref name=lpi/>
*[[broccoli]]<ref name=ods/>
*[[collard greens]]<ref name=lpi/>
*[[winter squash]]<ref name=lpi/><ref name=ods/>
*[[pumpkin]]<ref name=lpi/>
*[[cassava]]<ref>{{cite journal|doi=10.1002/jsfa.2740620411|title=Carotenoids in cassava: Comparison of open-column and HPLC methods of analysis|year=1993|last1=Adewusi|first1=Steve R A|last2=Bradbury|first2=J Howard|journal=Journal of the Science of Food and Agriculture|volume=62|issue=4|pages=375|bibcode=1993JSFA...62..375A }}</ref>
{{Div col end}}
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]] splits and the color is released into any liquid.<ref name=lpi/> 12 μg of dietary β-carotene supplies the equivalent of 1 μg of retinol, and 24&nbsp;μg of α-carotene or β-cryptoxanthin provides the equivalent of 1&nbsp;μg of retinol.<ref name=lpi/><ref name=ods/>

==Forms of carotene==
{{More citations needed section|date=October 2009}}
[[File:Alpha-carotene.svg|thumb|class=skin-invert-image|α-carotene]]
[[File:Beta-Carotin.svg|thumb|class=skin-invert-image|β-carotene]]
[[File:Gamma-carotene.svg|thumb|class=skin-invert-image|γ-carotene]]
[[File:Delta-carotene.svg|thumb|class=skin-invert-image|δ-carotene]]
The two primary [[isomer]]s of carotene, α-carotene and β-carotene, differ in the position of a [[double bond]] (and thus a hydrogen) in the cyclic group at one end (the right end in the diagram at right).

[[beta-Carotene|β-Carotene]] is the more common form and can be found in [[yellow]], [[Orange (colour)|orange]], and [[green]] leafy [[fruit]]s and [[vegetable]]s. As a [[rule of thumb]], 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]].

==β-Carotene and physiology==

===β-Carotene and cancer===
An article on the [[American Cancer Society]] 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.<ref>{{cite web|url=http://www.cancer.org/docroot/NWS/content/NWS_1_1x_Warning_Labels_on_Beta_Carotene_Called_For.asp |title=British Cancer Organization Calls for Warning Labels on Beta-Carotene |date=2000-07-31 |access-date=2007-03-15 |archive-url=https://web.archive.org/web/20061204074724/http://www.cancer.org/docroot/NWS/content/NWS_1_1x_Warning_Labels_on_Beta_Carotene_Called_For.asp |archive-date=2006-12-04 |url-status=dead }}</ref>

[[The New England Journal of Medicine]] published an article<ref>{{cite journal |author=The Alpha-Tocopherol, Beta Carotene Cancer Prevention Study Group |title=The effect of vitamin E and beta carotene on the incidence of lung cancer and other cancers in male smokers |journal=N Engl J Med |volume=330 |issue=15 |pages=1029–35 |year=1994 |pmid=8127329 |doi=10.1056/NEJM199404143301501 |doi-access=free }}</ref> in 1994 about a trial which examined the relationship between daily supplementation of β-carotene and [[vitamin E]] (α-[[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 Institute]] and The New England Journal of Medicine published articles in 1996<ref>{{cite journal |vauthors=Omenn GS, Goodman GE, Thornquist MD |title=Risk factors for lung cancer and for intervention effects in CARET, the Beta-Carotene and Retinol Efficacy Trial |journal=J Natl Cancer Inst |volume=88 |issue=21 |pages=1550–9 |year=1996 |pmid=8901853 |doi=10.1093/jnci/88.21.1550 |display-authors=etal|url=https://escholarship.org/content/qt8qk8w9zw/qt8qk8w9zw.pdf?t=ol280z |doi-access=free }}</ref><ref name=fn1>{{cite journal |vauthors=Omenn GS, Goodman GE, Thornquist MD |title=Effects of a combination of beta carotene and vitamin A on lung cancer and cardiovascular disease|journal=N Engl J Med |volume=334 |issue=18 |pages=1150–5 |year=1996 |pmid=8602180 |doi=10.1056/NEJM199605023341802 |display-authors=etal|url=https://escholarship.org/content/qt0mr2057n/qt0mr2057n.pdf?t=ngzuwv }}</ref> about a trial with a goal to determine if vitamin A (in the form of [[retinyl palmitate]]) and β-carotene (at about 30&nbsp;mg/day, which is 10 times the [[Reference Daily Intake]]) 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 [[tobacco smoking|smoking]] or [[asbestos]] exposure, causing the trial to be stopped early.<ref name=fn1 />

A review of all randomized controlled trials in the scientific literature by the [[Cochrane Collaboration]] published in ''[[Journal of the American Medical Association|JAMA]]'' in 2007 found that synthetic β-carotene ''increased'' mortality by 1–8% (Relative Risk 1.05, 95% confidence interval 1.01–1.08).<ref>{{cite journal |vauthors=Bjelakovic G, Nikolova D, Gluud LL, Simonetti RG, Gluud C |title=Mortality in randomized trials of antioxidant supplements for primary and secondary prevention: systematic review and meta-analysis|journal=JAMA |volume=297 |issue=8 |pages=842–57 |year=2007 |pmid=17327526 |doi=10.1001/jama.297.8.842}}
</ref> However, this meta-analysis included two large studies of smokers, so it is not clear that the results apply to the general population.<ref>
See the [http://jama.ama-assn.org/cgi/content/extract/298/4/401-a letter] to [[Journal of the American Medical Association|JAMA]] by Philip Taylor and [[Sanford Dawsey]] and the [http://jama.ama-assn.org/cgi/content/extract/298/4/402 reply] by the authors of the original paper.
</ref> 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]]. It provides them some relief from photosensitivity.<ref>{{cite journal|last1=Mathews-Ross|first1=Michelene|title=Beta Carotene Therapy for Erythropoietic Protoporphyria and Other Photosensitivity Diseases|journal=Archives of Dermatology|date=1977|volume=113|issue=9|pages=1229–1232|doi=10.1001/archderm.1977.01640090077011|pmid=900968}}</ref>

===Carotenemia===
{{Main|Carotenodermia}}
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]] of eyes (thus easily distinguishing it visually from [[jaundice]]). It is most commonly associated with consumption of an abundance of [[carrot]]s, but it also can be a [[medical sign]] of more dangerous conditions.

==Production==
[[File:Algaefarm.jpg|thumb|Algae farm ponds in [[Whyalla]], South Australia, used to produce β-carotene]]
Carotenes are produced in a general manner for other terpenoids and terpenes, i.e. by coupling, cyclization, and oxygenation reactions of [[isoprene]] derivatives. [[Lycopene]] is the key precursor to carotenoids. It is formed by coupling of [[geranylgeranyl pyrophosphate]] and [[geranyllinally pyrophosphate]].<ref>{{cite book |doi=10.1002/0471238961.2005181602120504.a01.pub2|chapter=Terpenoids |title=Kirk-Othmer Encyclopedia of Chemical Technology |year=2006 |last1=Sell |first1=Charles S. |isbn=0471238961 }}</ref>

Most of the world's synthetic supply of carotene comes from a manufacturing complex located in [[Freeport, Texas]] and owned by [[DSM (company)|DSM]]. The other major supplier [[BASF]] also uses a chemical process to produce β-carotene. Together these suppliers account for about 85% of the β-carotene on the market.<ref>{{cite book|first=Charis M. |last=Galanakis|title=Carotenoids: Properties, Processing and Applications|publisher=Academic Press|location=London|year=2020|isbn=9780128173145|url=https://books.google.com/books?id=H7SrDwAAQBAJ}}</ref> In Spain [[Vitatene]] produces natural β-carotene from fungus ''[[Blakeslea trispora]]'', 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]]'' grown in harvesting ponds situated in [[Karratha, Western Australia]]. 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]], the [[industrial biotechnology]] company [[Biotrend]] is producing natural all-''trans''-β-carotene from a non-genetically modified bacteria of the genus ''[[Sphingomonas]]'' isolated from soil.

Carotenes are also found in [[palm oil]], corn, and in the milk of dairy cows,<ref>{{cite journal|last1=Ullah|first1=Rahat|last2=Khan|first2=Saranjam|last3=Ali|first3=Hina|last4=Bilal|first4=Muhammad|last5=Saleem|first5=Muhammad|date=2017-05-18|title=Identification of cow and buffalo milk based on Beta carotene and vitamin-A concentration using fluorescence spectroscopy|journal=PLOS ONE|volume=12|issue=5|pages=e0178055|doi=10.1371/journal.pone.0178055|issn=1932-6203|pmc=5436857|pmid=28542353|bibcode=2017PLoSO..1278055U|doi-access=free}}</ref> 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 cattle|Guernsey]] 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.<ref>{{cite book|url=https://books.google.com/books?id=zSHMz5OwevwC&pg=PA414|title=Biology of Termites|last=Krishna|first=Kumar|publisher=Elsevier|year=2012|isbn=9780323144582|pages=414}}</ref>

===Synthesis===
There are currently two commonly used methods of [[total synthesis]] of β-carotene. The first was developed by [[BASF]] and is based on the [[Wittig reaction]] with Wittig himself as patent holder:<ref name="β-Carotin-1">Wittig G.; Pommer H.: ''DBP 954247, '''1956'''</ref><ref name="β-Carotin-2">Wittig G.; Pommer H. (1959). ''Chem. Abstr''. 53: 2279</ref>

[[File:Wittig-9.svg|center|class=skin-invert-image|Carotene synthesis by Wittig|500px]]

The second is a [[Grignard reaction]],<ref>{{cite patent
| country = US <!-- two letter country code -->
| number = 2609396 <!-- patent or patent application publication number -->
| status = patent <!-- application/patent -->
| title = Compounds with the carbon skeleton of beta-carotene and process for the manufacture thereof <!-- title -->
| pubdate = 1952-09-02 <!-- YYYY-MM-DD -->
| gdate = <!-- YYYY-MM-DD -->
| fdate = <!-- YYYY-MM-DD -->
| pridate = <!-- YYYY-MM-DD -->
| invent1 = Inhoffen Hans Herloff <!-- first inventor name -->
| invent2 = Pommer Horst <!-- second inventor name -->
| assign1 = <!-- first assignee name -->
| assign2 = <!-- second assignee name -->
| class = <!-- ECLA classification -->
}}</ref> 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 [[carotenoid]]s containing no oxygen. Carotenoids containing some oxygen are known as [[xanthophyll]]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 (letter)|psi]]'') 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]] is '''ψ,ψ-carotene'''

ζ-Carotene is the [[biosynthesis|biosynthetic]] [[precursor (chemistry)|precursor]] of [[neurosporene]], 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.<ref name=KO/> It is approved for use as a food additive in the EU (listed as additive E160a)<ref>UK Food Standards Agency: {{cite web |url=http://www.food.gov.uk/safereating/chemsafe/additivesbranch/enumberlist |title=Current EU approved additives and their E Numbers |access-date=2011-10-27}}</ref> Australia and New Zealand (listed as 160a)<ref>Australia New Zealand Food Standards Code{{cite web |url=http://www.comlaw.gov.au/Details/F2011C00827 |title=Standard 1.2.4 – Labelling of ingredients |date=8 September 2011 |access-date=2014-12-22}}</ref> and the US.<ref>US FDA: {{cite web |url=https://www.fda.gov/food/ingredientspackaginglabeling/foodadditivesingredients/ucm091048.htm |title=Food Additive Status List |website=[[Food and Drug Administration]] |access-date=2014-12-22}}</ref>

==See also==
* [[Antioxidant]]

==References==
{{Reflist}}

== External links ==
*{{MeshName|Carotene}}

{{Plant Pigments}}
{{Carrots}}
{{Carotenoids}}

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[[Category:Vitamin A]]
[[Category:Food colorings]]
[[Category:Carotenoids]]
[[Category:Hydrocarbons]]
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