Anthocyanin

Anthocyanin

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Not to be confused with Anthocyanidin
Anthocyanidin
Anthocyanidins are common plant pigments. They are the sugar-free counterparts of anthocyanins based on the flavylium ion or 2-phenylchromenylium, which is a type of oxonium ion . They form a large group of polymethine dye. In particular anthocyanidins are salt derivatives of the...

, their sugarfree counterparts.


Anthocyanins (also anthocyans; from Greek
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...

: (anthos) = flower + (kyanos) = blue) are water-soluble
Solubility
Solubility is the property of a solid, liquid, or gaseous chemical substance called solute to dissolve in a solid, liquid, or gaseous solvent to form a homogeneous solution of the solute in the solvent. The solubility of a substance fundamentally depends on the used solvent as well as on...

 vacuolar
Vacuole
A vacuole is a membrane-bound organelle which is present in all plant and fungal cells and some protist, animal and bacterial cells. Vacuoles are essentially enclosed compartments which are filled with water containing inorganic and organic molecules including enzymes in solution, though in certain...

 pigment
Pigment
A pigment is a material that changes the color of reflected or transmitted light as the result of wavelength-selective absorption. This physical process differs from fluorescence, phosphorescence, and other forms of luminescence, in which a material emits light.Many materials selectively absorb...

s that may appear red, purple, or blue according to pH
PH
In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...

. They belong to a parent class of molecules called flavonoids synthesized via the phenylpropanoid
Phenylpropanoid
The phenylpropanoids are a diverse family of organic compounds that are synthesized by plants from the amino acid phenylalanine. Their name is derived from the six-carbon, aromatic phenyl group and the three-carbon propene tail of cinnamic acid, which is synthesized from phenylalanine in the first...

 pathway; they are odorless and nearly flavorless, contributing to taste as a moderately astringent
Astringent
An astringent substance is a chemical compound that tends to shrink or constrict body tissues, usually locally after topical medicinal application. The word "astringent" derives from Latin adstringere, meaning "to bind fast"...

 sensation. Anthocyanins occur in all tissues
Biological tissue
Tissue is a cellular organizational level intermediate between cells and a complete organism. A tissue is an ensemble of cells, not necessarily identical, but from the same origin, that together carry out a specific function. These are called tissues because of their identical functioning...

 of higher plants, including leaves
Leaf
A leaf is an organ of a vascular plant, as defined in botanical terms, and in particular in plant morphology. Foliage is a mass noun that refers to leaves as a feature of plants....

, stems
Plant stem
A stem is one of two main structural axes of a vascular plant. The stem is normally divided into nodes and internodes, the nodes hold buds which grow into one or more leaves, inflorescence , conifer cones, roots, other stems etc. The internodes distance one node from another...

, root
Root
In vascular plants, the root is the organ of a plant that typically lies below the surface of the soil. This is not always the case, however, since a root can also be aerial or aerating . Furthermore, a stem normally occurring below ground is not exceptional either...

s, flowers, and fruit
Fruit
In broad terms, a fruit is a structure of a plant that contains its seeds.The term has different meanings dependent on context. In non-technical usage, such as food preparation, fruit normally means the fleshy seed-associated structures of certain plants that are sweet and edible in the raw state,...

s. Anthoxanthin
Anthoxanthin
Anthoxanthins are a type of flavonoid pigments in plants. Anthoxanthins are water-soluble pigments which range in color from white or colorless to a creamy to yellow, often on petals of flowers. These pigments are generally whiter in an acid medium and yellowed in an alkaline medium. They are...

s are their clear, white to yellow counterparts occurring in plants. Anthocyanins are derivatives of anthocyanidins, which include pendant sugars.

Function




In flowers, bright-reds and -purples are adaptive for attracting pollinators. In fruits, the colorful skins also attract the attention of animals, which may eat the fruits and disperse the seeds. In photosynthetic tissues (such as leaves and sometimes stems), anthocyanins have been shown to act as a "sunscreen", protecting cells from high-light damage by absorbing blue-green and UV light, thereby protecting the tissues from photoinhibition
Photoinhibition
Photoinhibition is light-induced reduction in the photosynthetic capacity of a plant, alga, or cyanobacterium. Photosystem II is more sensitive to light than the rest of the photosynthetic machinery, and most researchers define the term as light-induced damage to PSII...

, or high-light stress. This has been shown to occur in red juvenile leaves, autumn leaves, and broad-leaf evergreen leaves that turn red during the winter. It has also been proposed that red coloration of leaves may camouflage leaves from herbivores blind to red wavelengths, or signal unpalatability, since anthocyanin synthesis often coincides with synthesis of unpalatable phenolic compounds.

In addition to their role as light-attenuators, anthocyanins also act as powerful antioxidant
Antioxidant
An antioxidant is a molecule capable of inhibiting the oxidation of other molecules. Oxidation is a chemical reaction that transfers electrons or hydrogen from a substance to an oxidizing agent. Oxidation reactions can produce free radicals. In turn, these radicals can start chain reactions. When...

s. However, it is not clear as to whether anthocyanins can significantly contribute to scavenging of free-radicals produced through metabolic processes in leaves, since they are located in the vacuole and, thus, spatially separated from metabolic reactive oxygen species. Some studies have shown that hydrogen peroxide produced in other organelles can be neutralized by vacuolar anthocyanin.

pH indicator


Anthocyanin is also used to monitor levels of ionic hydrogen in solutions. It is pink in acidic solutions (pH
PH
In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...

 < 7), purple in neutral solutions (pH ~ 7), greenish-yellow in alkaline solutions (pH > 7), and colourless in very alkaline solutions where the pigment is completely reduced.

Occurrence



Food source Anthocyanin content
in mg per 100 g
açaí  320
blackcurrant
Blackcurrant
Blackcurrant, Ribes nigrum, is a species of Ribes berry native to central and northern Europe and northern Asia, and is a perennial....

 
190-270
chokeberry
Chokeberry
Aronia, the chokeberries, are two to three species of deciduous shrubs in the family Rosaceae, native to eastern North America. They are most commonly found in wet woods and swamps. Chokeberries are cultivated as ornamental plants and also because they are very high in antioxidant pigment...

 
1,480
eggplant  750
orange
Orange (fruit)
An orange—specifically, the sweet orange—is the citrus Citrus × sinensis and its fruit. It is the most commonly grown tree fruit in the world....

 
~200
Marion blackberry
Blackberry
The blackberry is an edible fruit produced by any of several species in the Rubus genus of the Rosaceae family. The fruit is not a true berry; botanically it is termed an aggregate fruit, composed of small drupelets. The plants typically have biennial canes and perennial roots. Blackberries and...

 
317
black raspberry
Black raspberry
Black raspberry is a common name for three species of the genus Rubus:*Rubus leucodermis, native to western North America*Rubus occidentalis, native to eastern North America, the species that is commercially harvested, particularly in the Pacific Northwest, from developed cultivars.*Rubus coreanus,...

 
589
raspberry
Raspberry
The raspberry or hindberry is the edible fruit of a multitude of plant species in the genus Rubus, most of which are in the subgenus Idaeobatus; the name also applies to these plants themselves...

 
365
wild blueberry
Blueberry
Blueberries are flowering plants of the genus Vaccinium with dark-blue berries and are perennial...

 
558
cherry
Cherry
The cherry is the fruit of many plants of the genus Prunus, and is a fleshy stone fruit. The cherry fruits of commerce are usually obtained from a limited number of species, including especially cultivars of the wild cherry, Prunus avium....

 
350-400
redcurrant
Redcurrant
The redcurrant , Ribes rubrum, is a member of the genus Ribes in the gooseberry family Grossulariaceae, native to parts of western Europe...

 
80-420
red grape
Grape
A grape is a non-climacteric fruit, specifically a berry, that grows on the perennial and deciduous woody vines of the genus Vitis. Grapes can be eaten raw or they can be used for making jam, juice, jelly, vinegar, wine, grape seed extracts, raisins, molasses and grape seed oil. Grapes are also...

 
888
red wine
Wine
Wine is an alcoholic beverage, made of fermented fruit juice, usually from grapes. The natural chemical balance of grapes lets them ferment without the addition of sugars, acids, enzymes, or other nutrients. Grape wine is produced by fermenting crushed grapes using various types of yeast. Yeast...

 
24-35
purple corn  1,642


Anthocyanins are found in the cell vacuole, mostly in flowers and fruit
Fruit
In broad terms, a fruit is a structure of a plant that contains its seeds.The term has different meanings dependent on context. In non-technical usage, such as food preparation, fruit normally means the fleshy seed-associated structures of certain plants that are sweet and edible in the raw state,...

s but also in leaves
Leaf
A leaf is an organ of a vascular plant, as defined in botanical terms, and in particular in plant morphology. Foliage is a mass noun that refers to leaves as a feature of plants....

, stems, and root
Root
In vascular plants, the root is the organ of a plant that typically lies below the surface of the soil. This is not always the case, however, since a root can also be aerial or aerating . Furthermore, a stem normally occurring below ground is not exceptional either...

s. In these parts, they are found predominantly in outer cell layers such as the epidermis
Epidermis (botany)
The epidermis is a single-layered group of cells that covers plants' leaves, flowers, roots and stems. It forms a boundary between the plant and the external environment. The epidermis serves several functions, it protects against water loss, regulates gas exchange, secretes metabolic compounds,...

 and peripheral mesophyll cells.

Most frequent in nature are the glycosides of cyanidin
Cyanidin
Cyanidin is a natural organic compound. It is a particular type of anthocyanidin . It is a pigment found in many red berries including but not limited to grapes, bilberry, blackberry, blueberry, cherry, cranberry, elderberry, hawthorn, loganberry, acai berry and raspberry...

, delphinidin
Delphinidin
Delphinidin is an anthocyanidin, a primary plant pigment, and also an antioxidant. Delphinidin gives blue hues to flowers like violas and delphiniums...

, malvidin
Malvidin
Malvidin is an O-methylated anthocyanidin. As a primary plant pigment, its glycosides are highly abundant in nature. It is responsible primarily for the color of red wine, Vitis vinifera being one of its sources...

, pelargonidin
Pelargonidin
Pelargonidin is an anthocyanidin, a type of plant pigment. Like all anthocyanins, it is an antioxidant. It produces a characteristic orange color, and can be found in red geraniums, and ripe raspberries and strawberries, as well as blueberries, blackberries, plums and cranberries and pomegranates....

, peonidin
Peonidin
Peonidin is an O-methylated anthocyanidin, and a primary plant pigment. Peonidin gives purplish-red hues to flowers such as the peony, from which it takes its name, and roses. It is also present in some blue flowers, such as the morning glory....

, and petunidin
Petunidin
Petunidin is an O-methylated anthocyanidin. It is a natural organic compound and a particular type of anthocyanidin. It is a dark-red or purple water-soluble pigment found in many redberries including chokeberries , Saskatoon berries or different species of grape , and...

. Roughly 2% of all hydrocarbon
Hydrocarbon
In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons from which one hydrogen atom has been removed are functional groups, called hydrocarbyls....

s fixated in photosynthesis are converted into flavonoids and their derivatives such as the anthocyanins. There is no less than 109 tons of anthocyanins produced in nature per year. Not all land plants contain anthocyanin; in the Caryophyllales
Caryophyllales
Caryophyllales is an order of flowering plants that includes the cacti, carnations, amaranths, ice plants, and many carnivorous plants. Many members are succulent, having fleshy stems or leaves.-Description:...

 (including cactus
Cactus
A cactus is a member of the plant family Cactaceae. Their distinctive appearance is a result of adaptations to conserve water in dry and/or hot environments. In most species, the stem has evolved to become photosynthetic and succulent, while the leaves have evolved into spines...

, beet
Beet
The beet is a plant in the Chenopodiaceae family which is now included in Amaranthaceae family. It is best known in its numerous cultivated varieties, the most well known of which is the purple root vegetable known as the beetroot or garden beet...

s, and amaranth
Amaranth
Amaranthus, collectively known as amaranth, is a cosmopolitan genus of herbs. Approximately 60 species are recognized, with inflorescences and foliage ranging from purple and red to gold...

), they are replaced by betalain
Betalain
Betalains are a class of red and yellow indole-derived pigments found in plants of the Caryophyllales, where they replace anthocyanin pigments. Betalains also occur in some higher order fungi. They are most often noticeable in the petals of flowers, but may color the fruits, leaves, stems, and...

s. However, anthocyanins and betalains have never been found in the same plant.

Plants rich in anthocyanins are Vaccinium
Vaccinium
Vaccinium is a genus of shrubs or dwarf shrubs in the plant Family Ericaceae. The fruit of many species are eaten by humans and some are of commercial importance, including the cranberry, blueberry, bilberry or whortleberry, lingonberry or cowberry, and huckleberry...

 species, such as blueberry
Blueberry
Blueberries are flowering plants of the genus Vaccinium with dark-blue berries and are perennial...

, cranberry
Cranberry
Cranberries are a group of evergreen dwarf shrubs or trailing vines in the subgenus Oxycoccus of the genus Vaccinium. In some methods of classification, Oxycoccus is regarded as a genus in its own right...

, and bilberry
Bilberry
Bilberry is any of several species of low-growing shrubs in the genus Vaccinium , bearing edible berries. The species most often referred to is Vaccinium myrtillus L., but there are several other closely related species....

, Rubus
Rubus
Rubus is a large genus of flowering plants in the rose family, Rosaceae, subfamily Rosoideae. Raspberries, blackberries, and dewberries are common, widely distributed members of the genus. Most of these plants have woody stems with prickles like roses; spines, bristles, and gland-tipped hairs are...

 berries including black raspberry
Black raspberry
Black raspberry is a common name for three species of the genus Rubus:*Rubus leucodermis, native to western North America*Rubus occidentalis, native to eastern North America, the species that is commercially harvested, particularly in the Pacific Northwest, from developed cultivars.*Rubus coreanus,...

, red raspberry, and blackberry
Blackberry
The blackberry is an edible fruit produced by any of several species in the Rubus genus of the Rosaceae family. The fruit is not a true berry; botanically it is termed an aggregate fruit, composed of small drupelets. The plants typically have biennial canes and perennial roots. Blackberries and...

, blackcurrant
Blackcurrant
Blackcurrant, Ribes nigrum, is a species of Ribes berry native to central and northern Europe and northern Asia, and is a perennial....

, cherry
Cherry
The cherry is the fruit of many plants of the genus Prunus, and is a fleshy stone fruit. The cherry fruits of commerce are usually obtained from a limited number of species, including especially cultivars of the wild cherry, Prunus avium....

, eggplant peel
Peel (fruit)
Peel, also known as rind or skin, is the outer protective layer of a fruit or vegetable which could be peeled off. The rind is usually the botanical exocarp, but the term exocarp does also include the hard cases of nuts, which are not named peels since they are not peeled off by hand or peeler, but...

, black rice
Black rice
Black rice is a kind of sticky rice which is one of several black colored heirloom plants producing rice variants such as Indonesian black rice and Thai Jasmine Black Rice. Black rice is high in nutritional value and contains 18 amino acids, iron , zinc, copper, carotene, anthocyanin and several...

, Concord grape
Concord grape
Concord grapes are a cultivar derived from the grape species Vitis labrusca which are used as table grapes, wine grapes and juice grapes....

, muscadine grape, red cabbage
Red Cabbage
The red cabbage is a sort of cabbage, also known as Red Kraut or Blue Kraut after preparation....

, and violet
Violet (plant)
Viola is a genus of flowering plants in the violet family Violaceae, with around 400–500 species distributed around the world. Most species are found in the temperate Northern Hemisphere; however, viola species are also found in widely divergent areas such as Hawaii, Australasia, and the Andes in...

 petals. Anthocyanins are less abundant in banana
Banana
Banana is the common name for herbaceous plants of the genus Musa and for the fruit they produce. Bananas come in a variety of sizes and colors when ripe, including yellow, purple, and red....

, asparagus
Asparagus
Asparagus officinalis is a spring vegetable, a flowering perennialplant species in the genus Asparagus. It was once classified in the lily family, like its Allium cousins, onions and garlic, but the Liliaceae have been split and the onion-like plants are now in the family Amaryllidaceae and...

, pea
Pea
A pea is most commonly the small spherical seed or the seed-pod of the pod fruit Pisum sativum. Each pod contains several peas. Peapods are botanically a fruit, since they contain seeds developed from the ovary of a flower. However, peas are considered to be a vegetable in cooking...

, fennel
Fennel
Fennel is a plant species in the genus Foeniculum . It is a member of the family Apiaceae . It is a hardy, perennial, umbelliferous herb, with yellow flowers and feathery leaves...

, pear
Pear
The pear is any of several tree species of genus Pyrus and also the name of the pomaceous fruit of these trees. Several species of pear are valued by humans for their edible fruit, but the fruit of other species is small, hard, and astringent....

, and potato
Potato
The potato is a starchy, tuberous crop from the perennial Solanum tuberosum of the Solanaceae family . The word potato may refer to the plant itself as well as the edible tuber. In the region of the Andes, there are some other closely related cultivated potato species...

, and may be totally absent in certain cultivar
Cultivar
A cultivar'Cultivar has two meanings as explained under Formal definition. When used in reference to a taxon, the word does not apply to an individual plant but to all those plants sharing the unique characteristics that define the cultivar. is a plant or group of plants selected for desirable...

s of green gooseberries.

The highest recorded amount appears to be specifically in the seed coat of black soybean
Soybean
The soybean or soya bean is a species of legume native to East Asia, widely grown for its edible bean which has numerous uses...

 (Glycine max L. Merr.) containing some 2,000 mg per 100 g and in skins and pulp of black chokeberry
Chokeberry
Aronia, the chokeberries, are two to three species of deciduous shrubs in the family Rosaceae, native to eastern North America. They are most commonly found in wet woods and swamps. Chokeberries are cultivated as ornamental plants and also because they are very high in antioxidant pigment...

 (Aronia melanocarpa L.) (table). However, the Amazonian palmberry, açaí, having about 320 mg per 100 g of which cyanidin-3-glucoside is the most prevalent individual anthocyanin (approximately 10 mg per 100 g), is also a high-content source for which only a small fraction of total anthocyanins has been determined to date. Due to critical differences in sample origin, preparation and extraction methods determining anthocyanin content, the values presented in the adjoining table are not directly comparable.

Nature, primitive agriculture, 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. Tomatoes have been bred conventionally for high anthocyanin content by crossing wild relatives with the common tomato
Tomato
The word "tomato" may refer to the plant or the edible, typically red, fruit which it bears. Originating in South America, the tomato was spread around the world following the Spanish colonization of the Americas, and its many varieties are now widely grown, often in greenhouses in cooler...

 to transfer a gene
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...

 called the anthocyanin fruit tomato ("aft") gene into a larger and more palatable fruit.

Tomatoes have also been genetically modified with transcription factor
Transcription factor
In molecular biology and genetics, a transcription factor is a protein that binds to specific DNA sequences, thereby controlling the flow of genetic information from DNA to mRNA...

s from snapdragon
SnapDragon
SnapDragon is a contemporary jazz band based in San Antonio, Texas. The group released their debut CD, "Stealing a Moment" on Humbug Records in 2008, and the 10-song CD soon broke the Top 100 in U.S radio airplay...

s to produce high levels of anthocyanins in the fruits. Anthocyanins can also be found in naturally ripened olives, and are partly responsible for the red and purple colors of some olives.

Autumn leaf color



Plants with abnormally high anthocyanin quantities are popular as ornamental plant
Ornamental plant
Ornamental plants are plants that are grown for decorative purposes in gardens and landscape design projects, as house plants, for cut flowers and specimen display...

s.
Many science textbooks incompletely state that autumn coloration
Autumn leaf color
Autumn leaf color is a phenomenon that affects the normally green leaves of many deciduous trees and shrubs by which they take on, during a few weeks in the autumn season, one or many colors that range from red to yellow...

 (including red) is the result of breakdown of green chlorophyll, which unmasks the already-present orange, yellow, and red pigments (carotenoid
Carotenoid
Carotenoids are tetraterpenoid organic pigments that are naturally occurring in the chloroplasts and chromoplasts of plants and some other photosynthetic organisms like algae, some bacteria, and some types of fungus. Carotenoids can be synthesized fats and other basic organic metabolic building...

s, xanthophyll
Xanthophyll
Xanthophylls are yellow pigments that form one of two major divisions of the carotenoid group. The name is from Greek xanthos + phyllon , due to their formation of the yellow band seen in early chromatography of leaf pigments...

s, and anthocyanins, respectively). While this is indeed the case for the carotenoids and xanthophylls (orange and yellow pigments), anthocyanins are not synthesized until the plant has begun breaking down the chlorophyll, it is presumed for photoprotection during nitrogen translocation.

Anthocyanidins: Flavylium cation derivatives


See Anthocyanidin
Anthocyanidin
Anthocyanidins are common plant pigments. They are the sugar-free counterparts of anthocyanins based on the flavylium ion or 2-phenylchromenylium, which is a type of oxonium ion . They form a large group of polymethine dye. In particular anthocyanidins are salt derivatives of the...

s article
.
Selected anthocyanidins and their substitutions
Anthocyanidin Basic structure R1 R2 R3 R4 R5 R6 R7
Aurantinidin
Aurantinidin
Aurantinidin is a water soluble, red plant dye. It is a member of the class of compounds known as anthocyanidins and is a hydroxy derivative of pelargonidin. Aurantinidin has been reported to occur in Impatients aurantiaca , and also in cultivars from genus Alstroemeria....

−H −OH −H −OH −OH −OH −OH
Cyanidin
Cyanidin
Cyanidin is a natural organic compound. It is a particular type of anthocyanidin . It is a pigment found in many red berries including but not limited to grapes, bilberry, blackberry, blueberry, cherry, cranberry, elderberry, hawthorn, loganberry, acai berry and raspberry...

−OH −OH −H −OH −OH −H −OH
Delphinidin
Delphinidin
Delphinidin is an anthocyanidin, a primary plant pigment, and also an antioxidant. Delphinidin gives blue hues to flowers like violas and delphiniums...

−OH −OH −OH −OH −OH −H −OH
Europinidin
Europinidin
Europinidin is an O-methylated anthocyanidin. It is a water soluble, bluish red plant dye. It is a rare O-methylated flavonoid, a derivative of delphinidin. It can be found in species of Plumbago and Ceratostigma.-External links:* *...

−OCH3 −OH −OH −OH −OCH3 −H −OH
Luteolinidin
Luteolinidin
Luteolinidin is a chemical compound belonging to the 3-deoxyanthocyanidins and that can be found in Sorghum bicolor.-Glycosides:Luteolinidin 5-O-β-D-[3-O-β-D-glucopyranosyl-2-O-acetylglucopyranoside] Luteolinidin is a chemical compound belonging to the 3-deoxyanthocyanidins and that can be found in...

−OH −OH −H −H −OH −H −OH
Pelargonidin
Pelargonidin
Pelargonidin is an anthocyanidin, a type of plant pigment. Like all anthocyanins, it is an antioxidant. It produces a characteristic orange color, and can be found in red geraniums, and ripe raspberries and strawberries, as well as blueberries, blackberries, plums and cranberries and pomegranates....

−H −OH −H −OH −OH −H −OH
Malvidin
Malvidin
Malvidin is an O-methylated anthocyanidin. As a primary plant pigment, its glycosides are highly abundant in nature. It is responsible primarily for the color of red wine, Vitis vinifera being one of its sources...

−OCH3 −OH −OCH3 −OH −OH −H −OH
Peonidin
Peonidin
Peonidin is an O-methylated anthocyanidin, and a primary plant pigment. Peonidin gives purplish-red hues to flowers such as the peony, from which it takes its name, and roses. It is also present in some blue flowers, such as the morning glory....

−OCH3 −OH −H −OH −OH −H −OH
Petunidin
Petunidin
Petunidin is an O-methylated anthocyanidin. It is a natural organic compound and a particular type of anthocyanidin. It is a dark-red or purple water-soluble pigment found in many redberries including chokeberries , Saskatoon berries or different species of grape , and...

−OH −OH −OCH3 −OH −OH −H −OH
Rosinidin
Rosinidin
Rosinidin is an O-methylated anthocyanidin. It is a pigment found in the flowers of Catharanthus roseus and, in lower concentration, in Primula rosea....

−OCH3 −OH −H −OH −OH −H −OCH3

Anthocyanins: Glycosides of anthocyanidins


The anthocyanins, anthocyanidins with sugar group(s), are mostly 3-glucosides of the anthocyanidins.
The anthocyanins are subdivided into the sugar
Sugar
Sugar is a class of edible crystalline carbohydrates, mainly sucrose, lactose, and fructose, characterized by a sweet flavor.Sucrose in its refined form primarily comes from sugar cane and sugar beet...

-free anthocyanidin
Anthocyanidin
Anthocyanidins are common plant pigments. They are the sugar-free counterparts of anthocyanins based on the flavylium ion or 2-phenylchromenylium, which is a type of oxonium ion . They form a large group of polymethine dye. In particular anthocyanidins are salt derivatives of the...

 aglycone
Aglycone
An aglycone is the non-sugar compound remaining after replacement of the glycosyl group from a glycoside by a hydrogen atom. The spelling aglycon is sometimes encountered .Classes of phytochemicals found in the aglycone and glycosides forms :...

s and the anthocyanin glycosides. As of 2003 more than 400 anthocyanins had been reported while more recent literature (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 are often used as pH
PH
In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...

 indicator
PH indicator
A pH indicator is a halochromic chemical compound that is added in small amounts to a solution so that the pH of the solution can be determined visually. Hence a pH indicator is a chemical detector for hydronium ions or hydrogen ions in the Arrhenius model. Normally, the indicator causes the...

, as they change from red in acid
Acid
An acid is a substance which reacts with a base. Commonly, acids can be identified as tasting sour, reacting with metals such as calcium, and bases like sodium carbonate. Aqueous acids have a pH of less than 7, where an acid of lower pH is typically stronger, and turn blue litmus paper red...

s to blue in base
Base (chemistry)
For the term in genetics, see base A base in chemistry is a substance that can accept hydrogen ions or more generally, donate electron pairs. A soluble base is referred to as an alkali if it contains and releases hydroxide ions quantitatively...

s.

Anthocyanins: Stability


Anthocyanins are thought to be subject to physiochemical degradation in vivo and in vitro. It has been demonstrated that B-ring hydroxylation status and pH mediate the degradation of anthocyanins to their phenolic acid and aldehyde constituents. Indeed, significant portions of ingested anthocyanins are likely to degrade to phenolic acids and aldehyde in vivo, following oral consumption. This characteristic confounds scientific isolation of specific anthocyanin mechanisms in vivo.

Biosynthesis



  1. Anthocyanin pigments are assembled like all other flavonoids from two different streams of chemical raw materials in the cell:
    • One stream involves the shikimate pathway to produce the amino acid phenylalanine
      Phenylalanine
      Phenylalanine is an α-amino acid with the formula C6H5CH2CHCOOH. This essential amino acid is classified as nonpolar because of the hydrophobic nature of the benzyl side chain. L-Phenylalanine is an electrically neutral amino acid, one of the twenty common amino acids used to biochemically form...

      . (see phenylpropanoid
      Phenylpropanoid
      The phenylpropanoids are a diverse family of organic compounds that are synthesized by plants from the amino acid phenylalanine. Their name is derived from the six-carbon, aromatic phenyl group and the three-carbon propene tail of cinnamic acid, which is synthesized from phenylalanine in the first...

      s)
    • The other stream produces 3 molecules of malonyl-CoA
      Malonyl-CoA
      Malonyl-CoA is a coenzyme A derivative.-Functions:It plays a key role in chain elongation in fatty acid biosynthesis and polyketide biosynthesis....

      , a C3 unit from a C2 unit (acetyl-CoA
      Acetyl-CoA
      Acetyl coenzyme A or acetyl-CoA is an important molecule in metabolism, used in many biochemical reactions. Its main function is to convey the carbon atoms within the acetyl group to the citric acid cycle to be oxidized for energy production. In chemical structure, acetyl-CoA is the thioester...

      ).
  2. These streams meet and are coupled together by the enzyme chalcone synthase (CHS), which forms an intermediate chalcone
    Chalconoid
    Chalconoids, also known as chalcones, are natural phenols related to chalcone. They form the central core for a variety of important biological compounds. They show antibacterial, antifungal, antitumor and anti-inflammatory properties...

    -like compound via a polyketide
    Polyketide
    Polyketides are secondary metabolites from bacteria, fungi, plants, and animals. Polyketides are usually biosynthesized through the decarboxylative condensation of malonyl-CoA derived extender units in a similar process to fatty acid synthesis...

     folding mechanism that is commonly found in plants.
  3. The chalcone is subsequently isomerized by the enzyme chalcone isomerase (CHI) to the prototype pigment naringenin
    Naringenin
    Naringenin is a flavanone, a type of flavonoid, that is considered to have a bioactive effect on human health as antioxidant, free radical scavenger, anti-inflammatory, carbohydrate metabolism promoter, and immune system modulator. It is the predominant flavanone in grapefruit.-Biological...

    .
  4. Naringenin is subsequently oxidized by enzymes such as flavanone hydroxylase (FHT or F3H), flavonoid 3' hydroxylase and flavonoid 3' 5'-hydroxylase.
  5. These oxidation products are further reduced by the enzyme dihydroflavonol 4-reductase (DFR) to the corresponding colorless leucoanthocyanidin
    Leucoanthocyanidin
    Leucoanthocyanidin are colorless chemical compounds related to anthocyanidins and anthocyanins. Leucoanthocyanins can be found in Anadenanthera peregrina and in several species of Nepenthes including Nepenthes rajah, Nepenthes burbidgeae, Nepenthes tentaculata, Nepenthes × alisaputrana and...

    s.
  6. It was believed that leucoanthocyanidins are the immediate precursors of the next enzyme, a dioxygenase referred to as anthocyanidin synthase (ANS) or leucoanthocyanidin dioxygenase (LDOX). It was recently shown however that flavan-3-ols, the products of leucoanthocyanidin reductase (LAR), are the true substrates of ANS/LDOX.
  7. The resulting, unstable anthocyanidins are further coupled to sugar molecules by enzymes like UDP-3-O-glucosyltransferase to yield the final relatively stable anthocyanins.


More than five enzymes are thus required to synthesize these pigments, each working in concert. Any even minor disruption in any of the mechanism 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 environmental adaptation, disease tolerance, and pest tolerance provided by anthocyanins.

Genetic analysis


The phenolic metabolic pathways and enzymes can be studied by mean of transgenesis
Transgenesis
thumb|300px|right|A diagram comparing the genetic changes achieved through conventional plant breeding, transgenesis and cisgenesisTransgenesis is the process of introducing an exogenous gene – called a transgene – into a living organism so that the organism will exhibit a new property and transmit...

 of genes. The Arabidopsis
Arabidopsis thaliana
Arabidopsis thaliana is a small flowering plant native to Europe, Asia, and northwestern Africa. A spring annual with a relatively short life cycle, arabidopsis is popular as a model organism in plant biology and genetics...

regulatory gene Production of Anthocyanin Pigment 1 (AtPAP1) can be expressed in other plant species.

Potential food value


Anthocyanins are considered secondary metabolite
Secondary metabolite
Secondary metabolites are organic compounds that are not directly involved in the normal growth, development, or reproduction of an organism. Unlike primary metabolites, absence of secondary metabolities does not result in immediate death, but rather in long-term impairment of the organism's...

s as a food additive
Food additive
Food additives are substances added to food to preserve flavor or enhance its taste and appearance.Some additives have been used for centuries; for example, preserving food by pickling , salting, as with bacon, preserving sweets or using sulfur dioxide as in some wines...

 with E number
E number
E numbers are number codes for food additives that have been assessed for use within the European Union . They are commonly found on food labels throughout the European Union. Safety assessment and approval are the responsibility of the European Food Safety Authority...

 E163 (INS number 163); they are approved for use as a food additive in the EU and Australia and New Zealand.

Although anthocyanins are powerful antioxidants in vitro
In vitro
In vitro refers to studies in experimental biology that are conducted using components of an organism that have been isolated from their usual biological context in order to permit a more detailed or more convenient analysis than can be done with whole organisms. Colloquially, these experiments...

, it is unlikely this antioxidant property is conserved after the plant that produced the anthocyanins is consumed. As interpreted by the Linus Pauling Institute
Linus Pauling Institute
The Linus Pauling Institute is a research institute located at Oregon State University with a focus on health maintenance. The mission statement of the institute is three-fold. First, to determine the functional roles of micronutrients and phytochemicals in promoting optimal health and to treat or...

 and European Food Safety Authority
European Food Safety Authority
The European Food Safety Authority is an agency of the European Union that provides independent scientific advice and communication on existing and emerging risks associated with the food chain, created by European Regulation 178/2002....

, dietary anthocyanins and other flavonoids have little or no direct antioxidant food value following digestion. Unlike controlled test tube conditions, the fate of anthocyanins in vivo
In vivo
In vivo is experimentation using a whole, living organism as opposed to a partial or dead organism, or an in vitro controlled environment. Animal testing and clinical trials are two forms of in vivo research...

 shows they are poorly conserved (less than 5%), with most of what is absorbed existing as chemically-modified metabolites that become rapidly excreted.

The increase in antioxidant capacity of blood seen after the consumption of anthocyanin-rich foods may not be caused directly by the anthocyanins, but instead may result from increased uric acid
Uric acid
Uric acid is a heterocyclic compound of carbon, nitrogen, oxygen, and hydrogen with the formula C5H4N4O3. It forms ions and salts known as urates and acid urates such as ammonium acid urate. Uric acid is created when the body breaks down purine nucleotides. High blood concentrations of uric acid...

 levels derived from metabolism of flavonoids.

Dye-sensitized solar cells


Anthocyanins have been used in organic solar cell
Solar cell
A solar cell is a solid state electrical device that converts the energy of light directly into electricity by the photovoltaic effect....

s because of their strong light harvesting, and their ability to convert of this light energy into electrical energy. There are many benefits to using dye-sensitized solar cells
Dye-sensitized solar cells
A dye-sensitized solar cell is a low-cost solar cell belonging to the group of thin film solar cells. It is based on a semiconductor formed between a photo-sensitized anode and an electrolyte, a photoelectrochemical system...

 instead of traditional pn junction silicon cells, such as lower purity requirements, abundance of component materials such as titania (and potentially anthocyanins) as well as the fact they can be produced on flexible substrates, making them amenable to roll-to-roll printing processes.

Research on health benefit


Richly concentrated as pigments in berries, anthocyanins were the topics of research presented at a 2007 symposium on health benefits that may result from berry consumption. Laboratory-based evidence was provided for potential health effects against:
  • cancer
  • aging and neurological diseases
  • inflammation
  • diabetes
  • bacterial infections
  • fibrocystic disease


Cancer research on anthocyanins is the most advanced, where black raspberry
Raspberry
The raspberry or hindberry is the edible fruit of a multitude of plant species in the genus Rubus, most of which are in the subgenus Idaeobatus; the name also applies to these plants themselves...

 (Rubus occidentalis
Rubus occidentalis
Rubus occidentalis is a species of Rubus native to eastern North America. Its common name black raspberry is shared with the closely related western American species Rubus leucodermis...

L.) preparations were first used to inhibit chemically induced cancer of the rat esophagus
Esophagus
The esophagus is an organ in vertebrates which consists of a muscular tube through which food passes from the pharynx to the stomach. During swallowing, food passes from the mouth through the pharynx into the esophagus and travels via peristalsis to the stomach...

 by 30-60% and of the colon
Colon (anatomy)
The colon is the last part of the digestive system in most vertebrates; it extracts water and salt from solid wastes before they are eliminated from the body, and is the site in which flora-aided fermentation of unabsorbed material occurs. Unlike the small intestine, the colon does not play a...

 by up to 80%. Effective at both the initiation and promotion/progression stages of tumor development, black raspberries are a practical research tool and a promising therapeutic source, as they contain the richest contents of anthocyanins among native North American Rubus
Rubus
Rubus is a large genus of flowering plants in the rose family, Rosaceae, subfamily Rosoideae. Raspberries, blackberries, and dewberries are common, widely distributed members of the genus. Most of these plants have woody stems with prickles like roses; spines, bristles, and gland-tipped hairs are...

 berries.

Work on laboratory cancer models has shown that black raspberry anthocyanins inhibit promotion and progression of tumor cells by
  1. stalling growth of pre-malignant
    Malignant
    Malignancy is the tendency of a medical condition, especially tumors, to become progressively worse and to potentially result in death. Malignancy in cancers is characterized by anaplasia, invasiveness, and metastasis...

     cells
  2. accelerating the rate of cell turnover, called apoptosis
    Apoptosis
    Apoptosis is the process of programmed cell death that may occur in multicellular organisms. Biochemical events lead to characteristic cell changes and death. These changes include blebbing, cell shrinkage, nuclear fragmentation, chromatin condensation, and chromosomal DNA fragmentation...

    , effectively making the cancer cells die faster
  3. reducing inflammatory mediators that initiate tumor onset
  4. inhibiting growth of new blood vessels that nourish tumors, a process called angiogenesis
    Angiogenesis
    Angiogenesis is the physiological process involving the growth of new blood vessels from pre-existing vessels. Though there has been some debate over terminology, vasculogenesis is the term used for spontaneous blood-vessel formation, and intussusception is the term for the formation of new blood...

  5. minimizing cancer-induced DNA
    DNA
    Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...

     damage.


On a molecular level, berry anthocyanins were shown to turn off genes
Gênes
Gênes is the name of a département of the First French Empire in present Italy, named after the city of Genoa. It was formed in 1805, when Napoleon Bonaparte occupied the Republic of Genoa. Its capital was Genoa, and it was divided in the arrondissements of Genoa, Bobbio, Novi Ligure, Tortona and...

 involved with proliferation, inflammation and angiogenesis., while switching on apoptosis.

In 2007, black raspberry studies entered the next pivotal level of research – the human clinical trial
Clinical trial
Clinical trials are a set of procedures in medical research and drug development that are conducted to allow safety and efficacy data to be collected for health interventions...

 – for which several approved studies are underway to examine anti-cancer effects of black raspberries and cranberries
Cranberry
Cranberries are a group of evergreen dwarf shrubs or trailing vines in the subgenus Oxycoccus of the genus Vaccinium. In some methods of classification, Oxycoccus is regarded as a genus in its own right...

 on tumors in the esophagus, prostate
Prostate
The prostate is a compound tubuloalveolar exocrine gland of the male reproductive system in most mammals....

 and colon.
A growing body of evidence suggests that anthocyanins and anthocyanidins may possess analgesic properties in addition to neuroprotective and anti-inflammatory activities.

Anthocyanins also fluoresce; combined with their antioxidant properties, this can be a powerful tool for plant cell research, allowing live cell imaging for extended periods of time without a requirement for other fluorophores.

Use as Visual Markers to Mark Genetically Modified Materials


Anthocyanin production can be engineered into genetically modified materials to enable their visual identification

Further reading


Books
  • Andersen, O.M. Flavonoids: Chemistry, Biochemistry and Applications. CRC Press, Boca Raton FL 2006. ISBN 9780849320217.
  • Gould, K. / Davies, K. / Winefield, C. (eds.) Anthocyanins: Biosynthesis, Functions, and Applications. Springer, 2008. ISBN 9780387773346

Journal articles

External links