View source for Chemistry:Betalain

{{Short description|Class of chemical compounds}}
[[Image:Beets produce-1.jpg|thumb|The red color of beets comes from betalain pigments.]]
'''Betalains''' are a class of red and yellow [[Chemistry:Tyrosine|tyrosine]]-derived pigments found in plants of the order [[Biology:Caryophyllales|Caryophyllales]], where they replace [[Chemistry:Anthocyanin|anthocyanin]] pigments. Betalains also occur in some higher order fungi.<ref>{{cite journal |vauthors= Strack D, Vogt T, Schliemann W |title= Recent advances in betalain research |journal= Phytochemistry |volume= 62 |issue= 3 |pages= 247–69 |date= February 2003 |pmid= 12620337 |doi= 10.1016/S0031-9422(02)00564-2 }}</ref> They are most often noticeable in the petals of flowers, but may color the fruits, leaves, stems, and roots of plants that contain them. They include pigments such as those found in beets.

==Description==
The name "betalain" comes from the [[Social:Latin language|Latin]] name of the common beet (''Beta vulgaris''), from which betalains were first extracted. The deep red color of beets, [[Biology:Bougainvillea|bougainvillea]], [[Biology:Amaranth|amaranth]], and many [[Biology:Cactus|cacti]] results from the presence of betalain pigments.<ref name="Robinson 1963">{{cite book |last= Robinson |first= Trevor | name-list-style = vanc |year=1963 |title=The Organic Constituents of Higher Plants |page=292 |location= Minneapolis |publisher= Burgess Publishing }}</ref> The particular shades of red to purple are distinctive and unlike that of anthocyanin pigments found in most plants.

There are two categories of betalains:<ref name="Salisbury 1991">{{cite book |last1= Salisbury |first1= Frank B. | first2 = Cleon W. | last2 = Ross | name-list-style = vanc |year=1991 |title=Plant Physiology |edition=4th |pages=325–326 |location= Belmont, California |publisher= Wadsworth Publishing |isbn=978-0-534-15162-1 }}</ref>
* '''Betacyanins''' include the reddish to violet betalain pigments. Among the betacyanins present in plants include [[Chemistry:Betanin|betanin]], isobetanin, probetanin, and neobetanin.
* '''Betaxanthins''' are those betalain pigments which appear yellow to orange. Among the betaxanthins present in plants include [[Chemistry:Vulgaxanthin|vulgaxanthin]], miraxanthin, portulaxanthin, and [[Chemistry:Indicaxanthin|indicaxanthin]].

The physiological function of betalains in plants is uncertain, but there is some evidence that they may have fungicidal properties.<ref>{{cite journal |last= Kimler |first= L. M. | name-list-style = vanc |year=1975 |title=Betanin, the red beet pigment, as an antifungal agent |journal= Botanical Society of America, Abstracts of Papers |volume= 36 }}</ref> Additionally, betalains have been found in fluorescent flowers, though their role in these plants is also uncertain.<ref name="pmid16163341">{{cite journal | vauthors = Gandía-Herrero F, García-Carmona F, Escribano J | title = Botany: floral fluorescence effect | journal = Nature | volume = 437 | issue = 7057 | pages = 334 | year = 2005 | pmid = 16163341 | doi = 10.1038/437334a | bibcode = 2005Natur.437..334G | s2cid = 4408230 | doi-access = free }}</ref>

<gallery>
Gelber und roter Mangold.JPG|Swiss chard, showing one plant expressing yellow betaxanthins and another expressing red betacyanins
Cactus in Bloom 01.jpg|Flowers of the [[Biology:Cactus|cactus]] ''[[Biology:Mammillaria|Mammillaria]] sp.'' contain betalains.
Amaranthus caudatus0.jpg|Inflorescences of ''[[Biology:Amaranthus caudatus|Amaranthus caudatus]]'' (love-lies-bleeding) contain large quantities of betacyanins.
</gallery>

==Chemistry==
[[Image:Betanin.svg|thumb|Chemical structure of betanin]]
Betalains (betacyanins) were first isolated and its chemical structure discovered in 1960 at the University of Zurich by Dr. Tom Mabry.<ref>{{Cite web|title=Tom J. MABRY Obituary (1932 - 2015) Austin American-Statesman|url=https://www.legacy.com/us/obituaries/statesman/name/tom-mabry-obituary?id=18253732|access-date=2021-12-03|website=Legacy.com}}</ref> It was once thought that betalains were related to anthocyanins, the reddish pigments found in most plants. Both betalains and anthocyanins are water-soluble pigments found in the [[Biology:Vacuole|vacuole]]s of plant cells. However, betalains are structurally and chemically unlike anthocyanins and the two have never been found in the same plant together.<ref>{{cite book |title=Colorants |last=Francis |first=F.J. |name-list-style=vanc |year=1999 |publisher=Egan Press |isbn=978-1-891127-00-7 |url-access=registration |url=https://archive.org/details/colorants0000fran }}</ref><ref>{{cite journal |last= Stafford |first= Helen A. | name-list-style = vanc |title= Anthocyanins and betalains: evolution of the mutually exclusive pathways |journal= Plant Science |volume= 101 |issue= 2 |pages= 91–98 |year= 1994 |issn= 0168-9452 |doi= 10.1016/0168-9452(94)90244-5 }}</ref> For example, betalains contain [[Chemistry:Nitrogen|nitrogen]] whereas anthocyanins do not.<ref name="Robinson 1963" />

It is now known that betalains are aromatic [[Chemistry:Indole|indole]] derivatives synthesized from [[Chemistry:Tyrosine|tyrosine]]. They are not related chemically to the anthocyanins and are not even [[Chemistry:Flavonoid|flavonoid]]s.<ref>{{cite book |last1= Raven |first1= Peter H. | first2 = Ray F. | last2 = Evert | first3 = Susan E. | last3 = Eichhorn | name-list-style = vanc |year=2004 |title=Biology of Plants |edition=7th |page=465 |location= New York |publisher= W. H. Freeman and Company |isbn=978-0-7167-1007-3 }}</ref> Each betalain is a [[Chemistry:Glycoside|glycoside]], and consists of a sugar and a colored portion. Their synthesis is promoted by light.<ref name="Salisbury 1991" />

The most heavily studied betalain is [[Chemistry:Betanin|betanin]], also called beetroot red after the fact that it may be extracted from red beet roots. Betanin is a [[Chemistry:Glucoside|glucoside]], and hydrolyzes into the sugar [[Chemistry:Glucose|glucose]] and betanidin.<ref name="Robinson 1963" /> It is used as a food coloring agent, and the color is sensitive to pH. Other betalains known to occur in beets are isobetanin, probetanin, and neobetanin. The color and antioxidant capacity of betanin and indicaxanthin (betaxanthin derived of {{sm|l}}-proline) are affected by dielectric microwave heating.<ref>{{cite journal | vauthors = Gonçalves LC, Di Genova BM, Dörr FA, Pinto E, Bastos EL |display-authors=3 | title = Effect of dielectric microwave heating on the color and antiradical capacity of betanin | journal = Journal of Food Engineering | volume = 118 | issue = 1 | pages = 49–55 | year = 2013 | doi = 10.1016/j.jfoodeng.2013.03.022| doi-access = free }}</ref> Addition of TFE (2,2,2-trifluoroethanol) is reported to improve the hydrolytic stability of some betalains in aqueous solution.<ref>{{cite journal | vauthors = Bartoloni FH, Gonçalves LC, Rodrigues AC, Dörr FA, Pinto E, Bastos EL |display-authors=3 | year = 2013 | title = Photophysics and hydrolytic stability of betalains in aqueous trifluoroethanol | journal = Monatshefte für Chemie - Chemical Monthly | volume = 144 | pages = 567–571 | doi = 10.1007/s00706-012-0883-5 | issue = 4|s2cid=93924750 }}</ref> Furthermore, a betanin-[[Chemistry:Europium|europium(III)]] complex has been used to detect calcium dipicolinate in bacterial spores, including ''[[Biology:Bacillus anthracis|Bacillus anthracis]]'' and ''B. cereus''.<ref>{{cite journal | vauthors = Gonçalves LC, Da Silva SM, DeRose PC, Ando RA, Bastos EL |display-authors=3 | title = Beetroot-pigment-derived colorimetric sensor for detection of calcium dipicolinate in bacterial spores | journal = PLOS ONE | volume = 8 | issue = 9 | pages = e73701 | year = 2013 | pmid = 24019934 | pmc = 3760816 | doi = 10.1371/journal.pone.0073701 | bibcode = 2013PLoSO...873701G |doi-access=free }}</ref>

Other important betacyanins are amaranthine and isoamaranthine, isolated from species of ''[[Biology:Amaranthus|Amaranthus]]''.

=== Biosynthesis ===
[[File:Betalain pathway.svg|right|thumb|Betalain biosynthesis: 1. betalamic acid. 2. ''cyclo''-dopa. 3. amine or amino acid. 4. betanidin. 5. betaxanthin.]]
In the first step of the biosynthetic pathway, L-tyrosine is converted to L-3,4-dihydroxyphenylalanine ({{sm|l}}-DOPA) by 3-hydroxylation by a cytochrome P450 enzyme. For dopa, the biosynthesis branches: a) on the one hand, its oxidation occurs by a CYP enzyme to cyclo-dopa;<ref>{{cite journal |vauthors= Polturak G, Breitel D, Grossman N, Sarrion-Perdigones A, Weithorn E, Pliner M, Orzaez D, Granell A, Rogachev I, Aharoni A |display-authors=3 |title=Elucidation of the first committed step in betalain biosynthesis enables the heterologous engineering of betalain pigments in plants |journal= New Phytol |volume=210 |issue=1 |pages= 269–283 |year=2016 |doi=10.1111/nph.13796 |url=https://nph.onlinelibrary.wiley.com/doi/10.1111/nph.13796|doi-access=free }}</ref> (b) on the other hand, the aromatic ring of dopa is activated by a dopa-4,5-dioxygenase<ref>{{cite journal |vauthors= Christinet L, Burdet FX, Zaiko M, Hinz U, Zrÿd JP |display-authors=3|title= Characterization and Functional Identification of a Novel Plant 4,5-Extradiol Dioxygenase Involved in Betalain Pigment Biosynthesis in ''Portulaca grandiflora'' |journal=Plant Physiology |volume=134 |issue=1 |year=2004 |pages=265–274 |doi=10.1104/pp.103.031914 |url=https://academic.oup.com/plphys/article/134/1/265/6112200|doi-access=free |pmc=316306 }}</ref> opened to seco-dopa, from which betalamic acid is formed by spantane recyclization. This then reacts spontaneously with cyclo-dopa to form betanidine on the one hand, or on the other hand after its prior glucosylation by a cyclo-dopa glucosyltransferase<ref>{{cite journal |vauthors=Sasaki N, Adachi T, Koda T, Ozeki Y |title=Detection of UDP-glucose:cyclo-DOPA 5-O-glucosyltransferase activity in four o'clocks (''Mirabilis jalapa'' L.) |journal=FEBS Letters |volume=568 |issue=1-3|year=2004 |pages=159–162 |doi=10.1016/j.febslet.2004.04.097 |url=https://febs.onlinelibrary.wiley.com/doi/10.1016/j.febslet.2004.04.097}}</ref> to red-purple betanin, the simplest betacyan. In addition, betalamic acid reacts spontaneously with various amino acids or amines to form yellow-orange colored betaxanthins (see figure). The diversity of betacyans results from different [[Biology:Glycosylation|glucosylation]] of betanidine and its subsequent [[Biology:Acyl group|acylation]] with aliphatic and aromatic carboxylic acids.

===Semisynthetic derivatives===
[[File:Betalamic acid.svg|thumb|(S)-Betalamic acid]]
Betanin extracted from the red beet<ref>{{cite journal | vauthors = Gonçalves LC, Trassi MA, Lopes NB, Dörr FA, Santos MT, Baader WJ, Oliveira Bastos EL |display-authors=3 | year = 2012 | title = A comparative study of the purification of betanin | journal = Food Chem. | volume = 131 | pages = 231–238 | doi = 10.1016/j.foodchem.2011.08.067| doi-access = free }}</ref> was used as starting material for the [[Chemistry:Semisynthesis|semisynthesis]] of an artificial [[Chemistry:Coumarin|coumarin]]ic betalaine. The betanin was hydrolyzed to betalamic acid, and this was coupled to 7-amino-4-methylcoumarin. The resulting betalain was applied as a fluorescent probe for the live-cell imaging of ''Plasmodium''-infected erythrocytes.<ref>{{cite journal | vauthors = Gonçalves LC, Tonelli RR, Bagnaresi P, Mortara RA, Ferreira AG, Bastos EL |display-authors=3 | title = A nature-inspired betalainic probe for live-cell imaging of Plasmodium-infected erythrocytes | journal = PLOS ONE | volume = 8 | issue = 1 | pages = e53874 | year = 2013 | pmid = 23342028 | pmc = 3547039 | doi = 10.1371/journal.pone.0053874 | editor1-last = Sauer | bibcode = 2013PLoSO...853874G | editor1-first = Markus |doi-access=free }}</ref>

==Taxonomic significance==
Betalain pigments occur only in the Caryophyllales and some [[Biology:Basidiomycota|Basidiomycota]] (mushrooms),<ref name="Cronquist 1981">{{cite book |last= Cronquist |first= Arthur |name-list-style= vanc |year= 1981 |title= An Integrated System of Classification of Flowering Plants |pages= [https://archive.org/details/integratedsystem0000cron/page/235 235–9] |location= New York |publisher= Columbia University Press |isbn= 978-0-231-03880-5 |url= https://archive.org/details/integratedsystem0000cron/page/235 }}</ref> for instance Hygrophoraceae (waxcaps).<ref>{{Cite journal|last1=Lodge|first1=D. Jean|last2=Padamsee|first2=Mahajabeen|last3=Matheny|first3=P. Brandon|last4=Aime|first4=M. Catherine|last5=Cantrell|first5=Sharon A.|last6=Boertmann|first6=David|last7=Kovalenko|first7=Alexander|last8=Vizzini|first8=Alfredo|last9=Dentinger|first9=Bryn T. M.|display-authors=3|date=2013-10-06|title=Molecular phylogeny, morphology, pigment chemistry and ecology in Hygrophoraceae (Agaricales)|journal=Fungal Diversity|language=en|volume=64|issue=1|pages=1–99|doi=10.1007/s13225-013-0259-0|s2cid=220615978|issn=1560-2745|url=https://iris.unito.it/bitstream/2318/136089/1/1205754_Molecular%20phylogeny.pdf|doi-access=free}}</ref> Where they occur in plants, they sometimes coexist with [[Biology:Anthoxanthin|anthoxanthin]]s (yellow to orange [[Chemistry:Flavonoid|flavonoid]]s), but never occur in plant species with anthocyanins.<ref name="Stafford">{{cite journal | last=Stafford | first=Helen A. | title=Anthocyanins and betalains: evolution of the mutually exclusive pathways (Review)| journal=Plant Science| volume=101 | issue=2 | year=1994 | issn=0168-9452 | doi=10.1016/0168-9452(94)90244-5 | pages=91–98|url=https://kundoc.com/pdf-anthocyanins-and-betalains-evolution-of-the-mutually-exclusive-pathways-.html}}</ref>

Among the flowering plant [[Biology:Order|order]] Caryophyllales, most members produce betalains and lack anthocyanins. Of all the families in the Caryophyllales, only the [[Biology:Caryophyllaceae|Caryophyllaceae]] (carnation family) and [[Biology:Molluginaceae|Molluginaceae]] produce anthocyanins instead of betalains.<ref name="Cronquist 1981" /> The limited distribution of betalains among plants is a synapomorphy for the Caryophyllales, though their production has been lost in two families.

==Economic uses==
Betanin is commercially used as a natural food dye. It can cause beeturia (red urine) and red feces in some people who are unable to break it down. The interest of the food industry in betalains has grown since they were identified by ''[[In vitro|in vitro]]'' methods as [[Biology:Antioxidant|antioxidant]]s,<ref>{{cite journal | vauthors = Escribano J, Pedreño MA, García-Carmona F, Muñoz R | year = 1998 | title = Characterization of the antiradical activity of betalains from ''Beta vulgaris'' L. roots | journal = Phytochem. Anal. | volume = 9 | pages = 124–7 | doi = 10.1002/(SICI)1099-1565(199805/06)9:3<124::AID-PCA401>3.0.CO;2-0 | issue = 3 }}</ref> which may protect against oxidation of [[Medicine:Low-density lipoprotein|low-density lipoprotein]]s.<ref name="Tesoriere 2004">{{cite journal | vauthors = Tesoriere L, Allegra M, Butera D, Livrea MA | title = Absorption, excretion, and distribution of dietary antioxidant betalains in LDLs: potential health effects of betalains in humans | journal = The American Journal of Clinical Nutrition | volume = 80 | issue = 4 | pages = 941–5 | date = October 2004 | pmid = 15447903 | url = http://www.ajcn.org/cgi/content/abstract/80/4/941 | doi = 10.1093/ajcn/80.4.941 | doi-access = free | hdl = 10447/33347 | hdl-access = free }}</ref>

== See also ==
* Biological pigment

== References ==
{{reflist|32em}}

==External links==
*[https://web.archive.org/web/20071222051800/http://www.botgard.ucla.edu/html/botanytextbooks/generalbotany/shootfeatures/generalstructure/leafcolor/a0896tx.html Betalain synthesis diagram]

{{Plant Pigments}}
{{Glycosides}}

[[Category:Natural dyes]]
[[Category:Food antioxidants]]

{{Sourceattribution|Betalain}}