anthocyanin

File:orange violet pansies.jpg their dark purple pigmentation]]

In flowers, the coloration that is provided by anthocyanin accumulation may attract a wide variety of animal pollinators, while in fruits, the same coloration may aid in seed dispersal by attracting herbivorous animals to the potentially-edible fruits bearing these red, blue, or purple colors.

Anthocyanins may have a protective role in plants against extreme temperatures.{{Cite journal|last1=Qiu|first1=Zhengkun|last2=Wang|first2=Xiaoxuan|last3=Gao|first3=Jianchang|last4=Guo|first4=Yanmei|last5=Huang|first5=Zejun|last6=Du|first6=Yongchen|date=2016-03-04|title=The Tomato Hoffman's Anthocyaninless Gene Encodes a bHLH Transcription Factor Involved in Anthocyanin Biosynthesis That Is Developmentally Regulated and Induced by Low Temperatures|journal=PLOS ONE|volume=11|issue=3|pages=e0151067|doi=10.1371/journal.pone.0151067|issn=1932-6203|pmc=4778906|pmid=26943362|bibcode=2016PLoSO..1151067Q|doi-access=free}}{{Cite journal|last1=Breusegem|first1=Frank Van|last2=Dat|first2=James F.|date=2006-06-01|title=Reactive Oxygen Species in Plant Cell Death|journal=Plant Physiology|language=en|volume=141|issue=2|pages=384–390|doi=10.1104/pp.106.078295|issn=1532-2548|pmc=1475453|pmid=16760492}} Tomato plants protect against cold stress with anthocyanins countering reactive oxygen species, leading to a lower rate of cell death in leaves.

File:Spectra Chlorophyll ab oenin (1).PNG (malvidin 3O glucoside), a typical anthocyanin, showing that, while chlorophylls absorb in the blue and yellow/red parts of the visible spectrum, oenin absorbs mainly in the green part of the spectrum, where chlorophylls don't absorb at all.]]

The absorbance pattern responsible for the red color of anthocyanins may be complementary to that of green chlorophyll in photosynthetically active tissues such as young Quercus coccifera leaves. It may protect the leaves from attacks by herbivores that may be attracted by green color.{{cite journal |author=Karageorgou P |author2=Manetas Y |title=The importance of being red when young: anthocyanins and the protection of young leaves of Quercus coccifera from insect herbivory and excess light |journal=Tree Physiol |volume=26 |issue=5 |pages=613–621 |date=2006 |doi=10.1093/treephys/26.5.613 |pmid=16452075|doi-access=free }}

Anthocyanins are found in the cell vacuole, mostly in flowers and fruits, but also in leaves, stems, and roots. In these parts, they are found predominantly in outer cell layers such as the epidermis and peripheral mesophyll cells.

Most frequently occurring in nature are the glycosides of cyanidin, delphinidin, malvidin, pelargonidin, peonidin, and petunidin. Roughly 2% of all hydrocarbons fixed in photosynthesis are converted into flavonoids and their derivatives, such as the anthocyanins. Not all land plants contain anthocyanin; in the Caryophyllales (including cactus, beets, and amaranth), they are replaced by betalains. Anthocyanins and betalains have never been found in the same plant.{{cite book |title= Colorants |last= Francis |first= F.J. |date= 1999 |publisher= Egan Press |isbn= 978-1-891127-00-7 |url-access= registration |url= https://archive.org/details/colorants0000fran }}{{Cite journal |last= Stafford |first= Helen A. |title= Anthocyanins and betalains: evolution of the mutually exclusive pathways |journal= Plant Science |volume= 101 |issue= 2 |pages= 91–98 |date= 1994 |doi= 10.1016/0168-9452(94)90244-5 |bibcode= 1994PlnSc.101...91S }}

Sometimes bred purposely for high anthocyanin content, ornamental plants such as sweet peppers may have unusual culinary and aesthetic appeal.{{cite web|url=http://agresearchmag.ars.usda.gov/2006/sep/veg|title=Twice as Nice Breeding Versatile Vegetables|publisher=Agricultural Research Magazine, US Department of Agriculture|vauthors=Stommel J, Griesbach RJ|date=September 2006|access-date=2 February 2016}}

Anthocyanins occur in the flowers of many plants, such as the blue poppies of some Meconopsis species and cultivars.{{cite web | url = http://www.meconopsis.org/spages/colourrange.html | publisher = Meconopsis Group | title = Colour range within genus | access-date = 30 June 2018 | archive-date = 4 May 2020 | archive-url = https://web.archive.org/web/20200504023449/http://www.meconopsis.org/spages/colourrange.html | url-status = dead }} Anthocyanins have also been found in various tulip flowers, such as Tulipa gesneriana, Tulipa fosteriana and Tulipa eichleri.N. Marissen, W. G. van Doorn and U. van Meeteren, International Society for Horticultural Science {{google books|LnQfAQAAMAAJ|Proceedings of the Eighth International Symposium on Postharvest Physiology of Ornamental Plants, 2005|page=248}}

File:Red cabbage cross section 02.jpg

File:Aroniabär - (Aronia melanocarpa) - Ystad-2021.jpg), a rich source of anthocyanins.]]

Plants rich in anthocyanins are Vaccinium species, such as blueberry, cranberry, and bilberry; Rubus berries, including black raspberry, red raspberry, and blackberry; blackcurrant, cherry, eggplant (aubergine) peel, black rice, ube, Okinawan sweet potato, Concord grape, muscadine grape, red cabbage, and violet petals. Red-fleshed peaches and apples contain anthocyanins.{{cite journal |display-authors=3 |last1=Cevallos-Casals |first1=BA |last2=Byrne |first2=D |last3=Okie |first3=WR |last4=Cisneros-Zevallos |first4=L |title=Selecting new peach and plum genotypes rich in phenolic compounds and enhanced functional properties |journal=Food Chemistry |volume=96 |issue=2 |pages=273–328 |date=2006 |doi=10.1016/j.foodchem.2005.02.032}}{{cite journal|last1=Sekido|first1=Keiko|title=Efficient breeding system for red-fleshed apple based on linkage with S3-RNase allele in 'Pink Pearl'.|journal=HortScience|date=2010|volume=45|issue=4|pages=534–537|display-authors=etal|doi=10.21273/HORTSCI.45.4.534|doi-access=free}}{{cite journal |last1=Oki |first1=Tomoyuki |last2=Kano |first2=Mitsuyoshi |last3=Watanabe |first3=Osamu |last4=Goto |first4=Kazuhisa |last5=Boelsma |first5=Esther |last6=Ishikawa |first6=Fumiyasu |last7=Suda |first7=Ikuo |title=Effect of consuming a purple-fleshed sweet potato beverage on health-related biomarkers and safety parameters in Caucasian subjects with elevated levels of blood pressure and liver function biomarkers: a 4-week, open-label, non-comparative trial |journal=Bioscience of Microbiota, Food and Health |date=2016 |volume=35 |issue=3 |pages=129–136 |doi=10.12938/bmfh.2015-026|pmid=27508114 |pmc=4965517 }}{{cite journal |last1=Moriya |first1=Chiemi |last2=Hosoya |first2=Takahiro |last3=Agawa |first3=Sayuri |last4=Sugiyama |first4=Yasumasa |last5=Kozone |first5=Ikuko |last6=Shin-ya |first6=Kazuo |last7=Terahara |first7=Norihiko |last8=Kumazawa |first8=Shigenori |title=New acylated anthocyanins from purple yam and their antioxidant activity |journal=Bioscience, Biotechnology, and Biochemistry |date=7 April 2015 |volume=79 |issue=9 |pages=1484–1492 |doi=10.1080/09168451.2015.1027652|pmid=25848974 |s2cid=11221328 |doi-access=free }} Anthocyanins are less abundant in banana, asparagus, pea, fennel, pear, and potato, and may be totally absent in certain cultivars of green gooseberries.

The highest recorded amount appears to be specifically in the seed coat of black soybean (Glycine max L. Merr.) containing approximately 2 g per 100 g,{{Cite journal |last1= Choung |first1= Myoung-Gun |title= Isolation and determination of anthocyanins in seed coats of black soybean (Glycine max (L.) Merr.) |journal= J. Agric. Food Chem. |volume= 49 |issue= 12 |pages= 5848–51 |date=December 2001 |pmid= 11743773 |doi= 10.1021/jf010550w |first2= In-Youl |last2= Baek |first3= Sung-Taeg |last3= Kang |first4= Won-Young |last4= Han |first5= Doo-Chull |last5= Shin |first6= Huhn-Pal |last6= Moon |first7= Kwang-Hee |last7= Kang |display-authors=3}} in purple corn kernels and husks, and in the skins and pulp of black chokeberry (Aronia melanocarpa L.) (see table). Due to critical differences in sample origin, preparation, and extraction methods determining anthocyanin content,{{Cite journal |last1= Krenn |first1=L |title= Anthocyanin- and proanthocyanidin-rich extracts of berries in food supplements—analysis with problems |journal= Pharmazie |volume= 62 |issue= 11 |pages= 803–12 |date=November 2007 |pmid= 18065095 |first2= M |last2= Steitz |first3= C |last3= Schlicht |first4= H |last4= Kurth |first5= F |last5= Gaedcke |display-authors=3}}{{Cite journal |display-authors= 3 |last1= Siriwoharn |first1=T |last2= Wrolstad |first2=RE |last3=Finn |first3=CE |last4=Pereira |first4=CB |title= Influence of cultivar, maturity, and sampling on blackberry (Rubus L. Hybrids) anthocyanins, polyphenolics, and antioxidant properties |journal= J Agric Food Chem |volume= 52 |issue= 26 |pages= 8021–30 |date=December 2004 |pmid= 15612791 |doi= 10.1021/jf048619y}} the values presented in the adjoining table are not directly comparable.

Nature, traditional agriculture methods, and plant breeding have produced various uncommon crops containing anthocyanins, including blue- or red-flesh potatoes and purple or red broccoli, cabbage, cauliflower, carrots, and corn. Garden tomatoes have been subjected to a breeding program using introgression lines of genetically modified organisms (but not incorporating them in the final purple tomato) to define the genetic basis of purple coloration in wild species that originally were from Chile and the Galapagos Islands.{{cite web|url=http://extension.oregonstate.edu/gardening/purple-tomato-debuts-indigo-rose|author=Scott J|publisher=Oregon State University Extension Service, Corvallis|title=Purple tomato debuts as 'Indigo Rose'|date=27 January 2012|access-date=9 September 2014}} The variety known as "Indigo Rose" became available commercially to the agricultural industry and home gardeners in 2012. Investing tomatoes with high anthocyanin content doubles their shelf-life and inhibits growth of a post-harvest mold pathogen, Botrytis cinerea.{{Cite journal |doi= 10.1016/j.cub.2013.04.072 |pmid= 23707429 |title= Anthocyanins Double the Shelf Life of Tomatoes by Delaying Overripening and Reducing Susceptibility to Gray Mold |journal= Current Biology |volume= 23 |issue= 12 |pages= 1094–100 |date= 2013 |last1= Zhang |first1= Y. |last2= Butelli |first2= E. |last3= De Stefano |first3= R. |last4= Schoonbeek |first4= H. J. |last5= Magusin |first5= A. |last6= Pagliarani |first6= C. |last7= Wellner |first7= N. |last8= Hill |first8= L. |last9= Orzaez |first9= D. |last10= Granell |first10= A. |last11= Jones |first11= J. D. G. |last12= Martin |first12= C. |display-authors=3 |pmc=3688073|bibcode= 2013CBio...23.1094Z }}

Some tomatoes also have been modified genetically with transcription factors from snapdragons to produce high levels of anthocyanins in the fruits.{{Cite journal |last1=Butelli |first1=Eugenio |title= Enrichment of tomato fruit with health-promoting anthocyanins by expression of select transcription factors |journal= Nature Biotechnology |volume= 26 |issue= 11 |pages= 1301–8 |date=November 2008 |pmid= 18953354 |doi= 10.1038/nbt.1506 |first2=Lucilla |last2= Titta |first3=Marco |last3= Giorgio |first4=Hans-Peter |last4= Mock |first5=Andrea |last5= Matros |first6=Silke |last6= Peterek |first7=Elio G W M |last7= Schijlen |first8=Robert D |last8= Hall |first9=Arnaud G |last9= Bovy |first10=Jie |last10= Luo |first11=Cathie |last11= Martin |s2cid=14895646 |display-authors=3}} Anthocyanins also may be found in naturally ripened olives,{{Cite journal |last1=Agati |first1=Giovanni |title= Nondestructive evaluation of anthocyanins in olive (Olea europaea) fruits by in situ chlorophyll fluorescence spectroscopy |journal= Journal of Agricultural and Food Chemistry |volume= 53 |issue= 5 |pages= 1354–63 |date=March 2005 |pmid= 15740006 |doi= 10.1021/jf048381d |first2=Patrizia |last2= Pinelli |first3=Solange |last3= Cortés Ebner |first4=Annalisa |last4=Romani |first5=Aurélie |last5= Cartelat |first6=Zoran G. |last6= Cerovic |display-authors=3}}{{cite book |title= Producing Table Olives |publisher= Landlinks Press |chapter= The olive tree Olea europaea |pages= 17–66 |isbn= 978-0-643-09203-7 |chapter-url= https://books.google.com/books?id=bRu8MKt3iR0C&pg=PA48 |author= Stan Kailis |author2= David Harris |name-list-style= amp |date= 28 February 2007}} and are partly responsible for the red and purple colors of some olives.

Content of anthocyanins in the leaves of colorful plant foods such as purple corn, blueberries, or lingonberries, is about ten times higher than in the edible kernels or fruit.{{Cite journal |pmid= 19007127 |date= 2008 |last1= Li |first1= C. Y. |title= Corn husk as a potential source of anthocyanins |journal= Journal of Agricultural and Food Chemistry |volume= 56 |issue= 23 |pages= 11413–6 |last2= Kim |first2= H. W. |last3= Won |first3= S. R. |last4= Min |first4= H. K. |last5= Park |first5= K. J. |last6= Park |first6= J. Y. |last7= Ahn |first7= M. S. |last8= Rhee |first8= H. I. |doi= 10.1021/jf802201c |display-authors= 3 }}{{Cite journal |pmid= 23875756 |date= 2013 |last1 = Vyas |first1= P |title= Chemical analysis and effect of blueberry and lingonberry fruits and leaves against glutamate-mediated excitotoxicity |journal= Journal of Agricultural and Food Chemistry |volume= 61 |issue= 32 |pages= 7769–76 |last2= Kalidindi |first2= S |last3= Chibrikova |first3= L |last4= Igamberdiev |first4= A. U. |last5= Weber |first5= J. T. |doi= 10.1021/jf401158a |display-authors= 3 }}

The color spectrum of grape berry leaves may be analysed to evaluate the amount of anthocyanins. Fruit maturity, quality, and harvest time may be evaluated on the basis of the spectrum analysis.{{Cite journal |volume= 17 |issue= 3 |pages= 316–326 |date= February 2011 |title= On-the-go sensing of grape berry anthocyanins during commercial harvest: development and prospects |first1= R.G.V. |last1= Bramley |first2= M. |last2= Le Moigne |first3= S. |last3= Evain |first4= J. |last4= Ouzman |first5= L. |last5= Florin |first6= E.M. |last6= Fadaili |first7= C.J. |last7= Hinze |first8= Z.G. |last8= Cerovic |journal= Australian Journal of Grape and Wine Research |url= http://max2.ese.u-psud.fr/publications/BramleyRGV2011AJGWR.pdf |display-authors= 3 |doi= 10.1111/j.1755-0238.2011.00158.x |access-date= 7 March 2015 |archive-date= 19 October 2017 |archive-url= https://web.archive.org/web/20171019140639/http://max2.ese.u-psud.fr/publications/BramleyRGV2011AJGWR.pdf |url-status= dead }}

{{main|Autumn leaf color}}

File:Vaccinium uliginosum Autumn leaf color and Fruits.jpg result from production of anthocyanins.]]

The reds, purples, and their blended combinations responsible for autumn foliage are derived from anthocyanins. Unlike carotenoids, anthocyanins are not present in the leaf throughout the growing season, but are produced actively, toward the end of summer. They develop in late summer in the sap of leaf cells, resulting from complex interactions of factors inside and outside the plant. Their formation depends on the breakdown of sugars in the presence of light as the level of phosphate in the leaf is reduced.{{Cite book |last=Davies|first=Kevin M. |title=Plant pigments and their manipulation |publisher=Wiley-Blackwell |date=2004 |page=6 |isbn=978-1-4051-1737-1}} Orange leaves in autumn result from a combination of anthocyanins and carotenoids.

Anthocyanins are present in approximately 10% of tree species in temperate regions, although in certain areas such as New England, up to 70% of tree species may produce anthocyanins.{{cite journal |first1=Marco |last1=Archetti |first2=Thomas F. |last2=Döring |first3=Snorre B. |last3=Hagen |first4=Nicole M. |last4=Hughes |first5=Simon R. |last5=Leather |first6=David W. |last6=Lee |first7=Simcha |last7=Lev-Yadun |first8=Yiannis |last8=Manetas |first9=Helen J. |last9=Ougham |first10=Paul G. |last10=Schaberg |first11=Howard |last11=Thomas |title=Unravelling the evolution of autumn colours: an interdisciplinary approach |journal=Trends in Ecology & Evolution |volume=24 |pages=166–73 |date=2011 |doi=10.1016/j.tree.2008.10.006 |pmid=19178979 |issue=3 |display-authors=3}}

Anthocyanins are approved for use as food colorants in the European Union, Australia, and New Zealand, having colorant code E163.{{cite web |title=Current EU approved additives and their E Numbers |publisher=Food Standards Agency |location=United Kingdom |year=2010 |url=http://www.food.gov.uk/safereating/chemsafe/additivesbranch/enumberlist |access-date=12 August 2017}}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=27 October 2011}} In 2013, a panel of scientific experts for the European Food Safety Authority concluded that anthocyanins from various fruits and vegetables have been insufficiently characterized by safety and toxicology studies to approve their use as food additives. Extending from a safe history of using red grape skin extract and blackcurrant extracts to color foods produced in Europe, the panel concluded that these extract sources were exceptions to the ruling and were sufficiently shown to be safe.

Anthocyanin extracts are not specifically listed among approved color additives for foods in the United States; however, grape juice, red grape skin and many fruit and vegetable juices, which are approved for use as colorants, are rich in naturally occurring anthocyanins.{{cite web|url=https://www.fda.gov/ForIndustry/ColorAdditives/ColorAdditiveInventories/ucm115641.htm|archive-url=https://web.archive.org/web/20090611073852/http://www.fda.gov/ForIndustry/ColorAdditives/ColorAdditiveInventories/ucm115641.htm|url-status=dead|archive-date=11 June 2009|title=Summary of Color Additives for Use in the United States in Foods, Drugs, Cosmetics, and Medical Devices|publisher=US Food and Drug Administration|date=May 2015|access-date=29 June 2017}} No anthocyanin sources are included among approved colorants for drugs or cosmetics.{{cite web|title=Summary of Color Additives for Use in the United States in Foods, Drugs, Cosmetics, and Medical Devices|url=https://www.fda.gov/ForIndustry/ColorAdditives/ColorAdditiveInventories/ucm115641.htm|archive-url=https://web.archive.org/web/20090611073852/http://www.fda.gov/ForIndustry/ColorAdditives/ColorAdditiveInventories/ucm115641.htm|url-status=dead|archive-date=11 June 2009|publisher=US Food and Drug Administration|access-date=13 August 2017|date=May 2015}} When esterified with fatty acids, anthocyanins can be used as a lipophilic colorant for foods.{{Cite journal|last1=Marathe|first1=Sandesh J.|last2=Shah|first2=Nirali N.|last3=Bajaj|first3=Seema R.|last4=Singhal|first4=Rekha S.|date=2021-04-01|title=Esterification of anthocyanins isolated from floral waste: Characterization of the esters and their application in various food systems|url=https://www.sciencedirect.com/science/article/pii/S2212429220311901|journal=Food Bioscience|language=en|volume=40|pages=100852|doi=10.1016/j.fbio.2020.100852|s2cid=233070680|issn=2212-4292|url-access=subscription}}

Although anthocyanins have been shown to have antioxidant properties in vitro,{{Cite journal|last2=Morán Vieyra|first2=FE|last3=Mercadante|first3=AZ|last4=Borsarelli|first4=CD|date=October 2008|title=Singlet oxygen quenching by anthocyanin's flavylium cations|journal=Free Radical Research|volume=42|issue=10|pages=885–91|doi=10.1080/10715760802506349|pmid=18985487|first1=VV|display-authors=3|last1=De Rosso|s2cid=21174667|hdl=11336/54522|hdl-access=free}} there is no evidence for antioxidant effects in humans after consuming foods rich in anthocyanins.{{cite journal|title=Scientific Opinion on the substantiation of health claims related to various food(s)/food constituent(s) and protection of cells from premature aging, antioxidant activity, antioxidant content and antioxidant properties, and protection of DNA, proteins and lipids from oxidative damage pursuant to Article 13(1) of Regulation (EC) No 1924/20061|author=EFSA Panel on Dietetic Products, Nutrition and Allergies|journal=EFSA Journal|year=2010|volume=8|issue=2|page=1489|doi=10.2903/j.efsa.2010.1752|doi-access=free}}{{Cite journal|date=2006|title=Consumption of flavonoid-rich foods and increased plasma antioxidant capacity in humans: cause, consequence, or epiphenomenon?|journal=Free Radic. Biol. Med.|volume=41|issue=12|pages=1727–46|doi=10.1016/j.freeradbiomed.2006.04.033|pmid=17157175|author=Lotito SB|author2=Frei B}}{{Cite journal|date=April 2004|title=Flavonoids: antioxidants or signalling molecules?|journal=Free Radical Biology & Medicine|volume=36|issue=7|pages=838–49|doi=10.1016/j.freeradbiomed.2004.01.001|pmid=15019969|author=Williams RJ|author2=Spencer JP|author3=Rice-Evans C}} Unlike controlled test-tube conditions, the fate of anthocyanins in vivo shows they are poorly conserved (less than 5%), with most of what is absorbed existing as chemically modified metabolites that are excreted rapidly."[http://www.eurekalert.org/pub_releases/2007-03/osu-sfn030507.php Studies force new view on biology of flavonoids]", by David Stauth, EurekAlert!. Adapted from a news release issued by Oregon State University The increase in antioxidant capacity of blood seen after the consumption of anthocyanin-rich foods may not be caused directly by the anthocyanins in the food, but instead by increased uric acid levels derived from metabolizing flavonoids (anthocyanin parent compounds) in the food. It is possible that metabolites of ingested anthocyanins are reabsorbed in the gastrointestinal tract from where they may enter the blood for systemic distribution and have effects as smaller molecules.

In a 2010 review of scientific evidence concerning the possible health benefits of eating foods claimed to have "antioxidant properties" due to anthocyanins, the European Food Safety Authority concluded that 1) there was no basis for a beneficial antioxidant effect from dietary anthocyanins in humans, 2) there was no evidence of a cause-and-effect relationship between the consumption of anthocyanin-rich foods and protection of DNA, proteins, and lipids from oxidative damage, and 3) there was no evidence generally for consumption of anthocyanin-rich foods having any "antioxidant", "anti-cancer", "anti-aging", or "healthy aging" effects.

{{main|Anthocyanidin}}

File:Anthocyanidine.svgs of anthocyanidins, the basic chemical structure of which is shown here.]]

The anthocyanins, anthocyanidins with sugar group(s), are mostly 3-glucosides of the anthocyanidins. The anthocyanins are subdivided into the sugar-free anthocyanidin aglycones and the anthocyanin glycosides.{{Citation needed|date=January 2023}} As of 2003, more than 400 anthocyanins had been reported,{{Cite journal |last1= Kong |first1= JM |title= Analysis and biological activities of anthocyanins |journal= Phytochemistry |volume= 64 |issue= 5 |pages= 923–33 |date=November 2003 |pmid= 14561507 |doi= 10.1016/S0031-9422(03)00438-2 |first2=LS |last2= Chia |first3=NK |last3= Goh |first4=TF |last4= Chia |first5=R |last5= Brouillard |bibcode= 2003PChem..64..923K |display-authors=3}} while later literature in early 2006, puts the number at more than 550 different anthocyanins. The difference in chemical structure that occurs in response to changes in pH, is the reason why anthocyanins often are used as pH indicators, as they change from red in acids to blue in bases through a process called halochromism.

Anthocyanins are thought to be subject to physiochemical degradation in vivo and in vitro. Structure, pH, temperature, light, oxygen, metal ions, intramolecular association, and intermolecular association with other compounds (copigments, sugars, proteins, degradation products, etc.) generally are known to affect the color and stability of anthocyanins.{{Cite book |last1= Andersen |first1= Øyvind M. |last2= Jordheim |first2= Monica |contribution= Anthocyanins- food applications |date = 2008 |title= 5th Pigments in Food congress- for quality and health |publisher= University of Helsinki |isbn = 978-952-10-4846-3}} B-ring hydroxylation status and pH have been shown to mediate the degradation of anthocyanins to their phenolic acid and aldehyde constituents.{{cite journal |display-authors=3 |last1=Woodward |first1=G |first2=P |last2=Kroon |first3= A |last3=Cassidy |first4= C |last4=Kay |title=Anthocyanin stability and recovery: implications for the analysis of clinical and experimental samples |journal=J. Agric. Food Chem. |volume=57 |issue=12 |pages=5271–8 |date=June 2009 |pmid=19435353 |doi=10.1021/jf900602b }} Indeed, significant portions of ingested anthocyanins are likely to degrade to phenolic acids and aldehyde in vivo, following consumption. This characteristic confounds scientific isolation of specific anthocyanin mechanisms in vivo.

File:Indicateur chou rouge.jpg extract at low pH (left) to high pH (right)]]

Anthocyanins generally are degraded at higher pH. However, some anthocyanins, such as petanin (petunidin 3-[6-O-(4-O-(E)-p-coumaroyl-O-α-{{sm|l}}-rhamnopyranosyl)-β-{{sm|d}}-glucopyranoside]-5-O-β-{{sm|d}}-glucopyranoside), are resistant to degradation at pH 8 and may be used effectively as a food colorant.{{cite journal|date=December 1998|title=Colour and stability of pure anthocyanins influenced by pH including the alkaline region|journal=Food Chemistry|volume=63|issue=4|pages=435–440|doi=10.1016/S0308-8146(98)00065-X|author=Fossen T|author2=Cabrita L|author3=Andersen OM|hdl=10198/3206|hdl-access=free}}

File:BlueTomato.jpg was used to produce P20 blue tomatoes]]

Anthocyanins may be used as pH indicators because their color changes with pH; they are red or pink in acidic solutions (pH < 7), purple in neutral solutions (pH ≈ 7), greenish-yellow in alkaline solutions (pH > 7), and colorless in very alkaline solutions, where the pigment is completely reduced.{{cite journal|date=1 December 1936|title=Potentiometric Study of the Flavins|url=http://www.jbc.org/content/116/2/587.full.pdf+html|journal=J. Biol. Chem.|volume=116|issue=2|pages=587–607|last1=Michaelis|first1=Leonor|last2=Schubert|first2=M.P.|last3=Smythe|first3=C.V.|doi=10.1016/S0021-9258(18)74634-6|doi-access=free}}

File:Blood orange sliced.jpgs contribute distinctive pigmentation to blood oranges]]

1. Anthocyanin pigments are assembled like all other flavonoids from two different streams of chemical raw materials in the cell:
2. * One stream involves the shikimate pathway to produce the amino acid phenylalanine, (see phenylpropanoids)
3. * The other stream produces three molecules of malonyl-CoA, a C₃ unit from a C₂ unit (acetyl-CoA),{{Cite journal|date=1998|title=Anthocyanin|url=http://www.carnivorousplants.org/cpn/samples/Science273anthocyanin.htm|journal=Carnivorous Plant Newsletter|author=Jack Sullivan|access-date=6 October 2009|archive-url=https://web.archive.org/web/20091101035706/http://www.carnivorousplants.org/cpn/samples/Science273anthocyanin.htm|archive-date=1 November 2009 |url-status=live}}
4. These streams meet and are coupled together by the enzyme chalcone synthase, which forms an intermediate chalcone-like compound via a polyketide folding mechanism that is commonly found in plants,
5. The chalcone is subsequently isomerized by the enzyme chalcone isomerase to the prototype pigment naringenin,
6. Naringenin is subsequently oxidized by enzymes such as flavanone hydroxylase, flavonoid 3'-hydroxylase, and flavonoid 3',5'-hydroxylase,
7. These oxidation products are further reduced by the enzyme dihydroflavonol 4-reductase to the corresponding colorless leucoanthocyanidins,{{Cite journal |display-authors= 3 |last1= Nakajima |first1=J |first2= Y |last2= Tanaka |first3= M |last3= Yamazaki |first4= K|last4= Saito|title= Reaction mechanism from leucoanthocyanidin to anthocyanidin 3-glucoside, a key reaction for coloring in anthocyanin biosynthesis |journal= The Journal of Biological Chemistry |volume= 276 |issue= 28 |pages= 25797–803 |date=July 2001 |pmid= 11316805 |doi= 10.1074/jbc.M100744200 |doi-access= free }}
8. Leucoanthocyanidins once were believed to be the immediate precursors of the next enzyme, a dioxygenase referred to as anthocyanidin synthase, or, leucoanthocyanidin dioxygenase. Flavan-3-ols, the products of leucoanthocyanidin reductase (LAR), recently have been shown to be their true substrates,
9. The resulting unstable anthocyanidins are further coupled to sugar molecules by enzymes such as UDP-3-O-glucosyltransferase,{{cite journal |first1=N |display-authors=3 |last1=Kovinich |first2= A |last2= Saleem |first3= JT |last3= Arnason |first4= B |last4= Miki |title=Functional characterization of a UDP-glucose:flavonoid 3-O-glucosyltransferase from the seed coat of black soybean (Glycine max (L.) Merr.) |journal=Phytochemistry |volume=71 |issue=11–12 |pages=1253–63 |date=August 2010 |pmid=20621794 |doi=10.1016/j.phytochem.2010.05.009 |bibcode=2010PChem..71.1253K }} to yield the final relatively-stable anthocyanins.

Thus, more than five enzymes are required to synthesize these pigments, each working in concert. Even a minor disruption in any of the mechanisms of these enzymes by either genetic or environmental factors, would halt anthocyanin production. While the biological burden of producing anthocyanins is relatively high, plants benefit significantly from the environmental adaptation, disease tolerance, and pest tolerance provided by anthocyanins.

In anthocyanin biosynthetic pathway, L-phenylalanine is converted to naringenin by phenylalanine ammonialyase, cinnamate 4-hydroxylase, 4-coumarate CoA ligase, chalcone synthase, and chalcone isomerase. Then, the next pathway is catalyzed, resulting in the formation of complex aglycone and anthocyanin through composition by flavanone 3-hydroxylase, flavonoid 3'-hydroxylase, dihydroflavonol 4-reductase, anthocyanidin synthase, UDP-glucoside: flavonoid glucosyltransferase, and methyl transferase.{{cite journal |display-authors=3 |author=Da Qiu Zhao |author2=Chen Xia Han |author3=Jin Tao Ge |author4= Jun Tao |title=Isolation of a UDP-glucose: Flavonoid 5-O-glucosyltransferase gene and expression analysis of anthocyanin biosynthetic genes in herbaceous peony (Paeonia lactiflora Pall.) |journal=Electronic Journal of Biotechnology |volume=15 |issue=6 |date=15 November 2012 |doi=10.2225/vol15-issue6-fulltext-7 |doi-access=free }}

The phenolic metabolic pathways and enzymes may be studied by mean of transgenesis of genes. The Arabidopsis regulatory gene in the production of anthocyanin pigment 1 (AtPAP1) may be expressed in other plant species.{{cite journal |title= Purple canola: Arabidopsis PAP1 increases antioxidants and phenolics in Brassica napus leaves |first1=Xiang |last1=Li |journal= J. Agric. Food Chem. |date= 2010 |volume= 58 |issue= 3 |pages= 1639–1645 |doi= 10.1021/jf903527y |pmid= 20073469 |first2= Ming-Jun |last2= Gao |first3= Hong-Yu |last3= Pan |first4= De-Jun |last4= Cui |first5= Margaret Y. |last5= Gruber |display-authors=3 }}

Anthocyanins have been used in organic solar cells because of their ability to convert light energy into electrical energy.{{Cite journal |doi= 10.1021/jp972197w |title= Ultrafast Electron Injection: Implications for a Photoelectrochemical Cell Utilizing an Anthocyanin Dye-Sensitized {{chem|TiO|2}} Nanocrystalline Electrode |date= 1997 |first1= Nerine J. |last1= Cherepy |first2= Greg P. |last2= Smestad |first3= Michael |last3= Grätzel |first4= Jin Z. |last4= Zhang |journal= The Journal of Physical Chemistry B |volume= 101 |issue= 45 |pages= 9342–51 |url= http://solideas.com/papers/JPhysChemB.pdf}} The many benefits to using dye-sensitized solar cells instead of traditional p-n junction silicon cells, include lower purity requirements and abundance of component materials, as well as the fact that they may be produced on flexible substrates, making them amenable to roll-to-roll printing processes.{{Cite journal |last1= Grätzel |first1= Michael |title= Dye-sensitized solar cells |doi= 10.1016/S1389-5567(03)00026-1 |volume= 4 |issue= 2 |date=October 2003 |pages= 145–53 |journal= Journal of Photochemistry and Photobiology}}

Anthocyanins fluoresce, enabling a tool for plant cell research to allow live cell imaging without a requirement for other fluorophores.{{Cite journal |author= Wiltshire EJ |author2= Collings DA |title= New dynamics in an old friend: dynamic tubular vacuoles radiate through the cortical cytoplasm of red onion epidermal cells |journal= Plant & Cell Physiology |volume= 50 |issue= 10 |pages= 1826–39 |date=October 2009 |pmid= 19762337 |doi= 10.1093/pcp/pcp124|doi-access= free }} Anthocyanin production may be engineered into genetically modified materials to enable their identification visually.{{cite journal |last1= Kovinich |first1= N |last2=Saleem |first2= A |last3=Rintoul |first3= TL |last4=Brown |first4= DC |last5=Arnason |first5= JT |last6=Miki |first6= B |title=Coloring genetically modified soybean grains with anthocyanins by suppression of the proanthocyanidin genes ANR1 and ANR2 |journal=Transgenic Res. |volume=21 |issue=4 |pages=757–71 |date=August 2012 |pmid=22083247 |doi=10.1007/s11248-011-9566-y |s2cid= 15957685 |display-authors= 3}}

• Phenolic compounds in wine
• p-Coumaroylated anthocyanin

{{Reflist}}

• {{cite book |author=Andersen, O.M. |title=Flavonoids: Chemistry, Biochemistry and Applications |publisher=CRC Press |location=Boca Raton FL |date=2006 |isbn=978-0-8493-2021-7 }}
• {{cite book |editor1-last=Gould |editor1-first=K. |editor2-last=Davies |editor2-first=K. |editor3-last=Winefield |editor3-first=C. |title=Anthocyanins: Biosynthesis, Functions, and Applications |publisher=Springer |date=2008 |isbn=978-0-387-77334-6 }}

• [https://www.madsci.org/FAQs/anthocyanins.html Anthocyanins FAQ MadSci Network]

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