- Not to be confused with Anthocyanidin
Anthocyanidins are common plant pigments. They are the sugar-free counterparts of anthocyanins based on the flavylium ion or 2-phenylchromenylium . They form a large group of polymethine dye. In particular anthocyanidins are salt derivatives of the 2-phenylchromenylium cation, also known as...
, their sugar free counterparts.
Anthocyanins (from
GreekGreek , an independent branch of the Indo-European family of languages, is the language of the Greeks. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. In its ancient form, it is the language of classical...
:
(anthos) = flower +
(kyanos) = blue) are
water-solubleSolubility is the property of a solid, liquid, or gaseous chemical substance called solute to dissolve in a liquid solvent to form a homogeneous solution. The solubility of a substance strongly depends on the used solvent as well as on temperature and pressure...
vacuolarthumb|400px|Plant cell structurethumb|400px|Animal cell structureA vacuole is a membrane organelle which is present in all plant and fungal cells and some protist, animal and bacterial cells...
pigments that may appear red, purple, or blue according to
pHpH is a measure of the acidity or basicity of a solution. It is defined as the cologarithm of the activity of dissolved hydrogen ions . Hydrogen ion activity coefficients cannot be measured experimentally, so they are based on theoretical calculations...
. They belong to a parent class of molecules called flavonoids synthesized via the
phenylpropanoidPhenylpropanoids are a class of plant-derived organic compounds that are biosynthesized from the amino acid phenylalanine. They have a wide variety of functions, including defense against herbivores, microbial attack, or other sources of injury; as structural components of cell walls; as...
pathway; they are odorless and nearly flavorless, contributing to taste as a moderately stringent sensation. Anthocyanins occur in all
tissuesTissue is a cellular organizational level intermediate between cells and a complete organism. Hence, a tissue is an ensemble of cells, not necessarily identical, but from the same origin, that together carry out a specific function...
of higher plants, including
leavesIn botany, a leaf is an above-ground plant organ specialized for photosynthesis. For this purpose, a leaf is typically flat and thin. There is continued debate about whether the flatness of leaves evolved to expose the chloroplasts to more light or to increase the absorption of carbon dioxide. In...
,
stemsA 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 , cones or other stems etc. The internodes act as spaces that distance one node from another...
,
rootIn 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
fruitThe term fruit has different meanings dependent on context, and the term is not synonymous in food preparation and biology. Fruits are the means by which flowering plants disseminate seeds, and the presence of seeds indicates that a structure is most likely a fruit, though not all seeds come from...
s.
AnthoxanthinAnthoxanthins 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
photoinhibitionPhotoinhibition is light-induced reduction in the photosynthetic capacity of a plant, alga or a 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 Photosystem II...
, or high-light stress. This has been shown to occur in red juvenile leaves, autumn leaves, and broad-leaved 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
antioxidantAn antioxidant is a molecule capable of slowing or preventing the oxidation of other molecules. Oxidation is a chemical reaction that transfers electrons from a substance to an oxidizing agent. Oxidation reactions can produce free radicals, which start chain reactions that damage cells...
s. However, it is not clear 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.
Occurrence
| Food source |
Anthocyanin content
in mg per 100 g |
| açaí |
320 |
blackcurrantThe Blackcurrant is a species of Ribes berry native to central and northern Europe and northern Asia. It is also known as French "cassis"....
|
190-270 |
chokeberryThe chokeberries are two 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 compounds, like...
|
1,480 |
| eggplant |
750 |
orangeAn orange—specifically, the sweet orange—is the citrus Citrus ×sinensis and its fruit. The orange is a hybrid of ancient cultivated origin, possibly between pomelo and tangerine...
|
~200 |
Marion blackberryThe blackberry is an edible berry in the Rubus genus and the Rosaceae family. The fruit are botanically termed an aggregate fruit and they are produced on plants that typically have biennial canes and perennial roots. Blackberries and raspberries are also called caneberries or brambles...
|
317 |
| black raspberry Black raspberry is a common name for two closely related species of the genus Rubus:*Rubus leucodermis, native to western North America*Rubus occidentalis, native to eastern North America...
|
589 |
raspberryThe raspberry is the edible fruit of a multitude of plant species in the subgenus Idaeobatus of the genus Rubus; the name also applies to these plants themselves...
|
365 |
wild blueberryBlueberries are flowering plants of the genus Vaccinium with dark-blue berries. Species in the section Cyanococcus are the most common fruits sold as "blueberries" and are mainly native to North America. They are usually erect but sometimes prostrate shrubs varying in size from to tall...
|
558 |
cherryThe cherry is the fruit of many plants of the genus Prunus. It is a fleshy fruit that contains a single stony seed. The cherry fruits of commerce are usually obtained from a limited number of species, including especially cultivars of the wild cherry, Prunus avium.The name 'cherry', often as the...
|
350-400 |
redcurrantThe Red currant is a member of the genus Ribes in the gooseberry family Grossulariaceae, native to parts of western Europe . It is a deciduous shrub normally growing to 1-1.5 m tall, occasionally 2 m, with five-lobed leaves arranged spirally on the stems...
|
80-420 |
| red grape A grape is the non-climacteric fruit, botanically a true berry, that grows on the perennial and deciduous woody vines of the genus Vitis. Grapes can be eaten raw or used for making jam, juice, jelly, vinegar, wine, grape seed extracts, raisins, and grape seed oil...
|
888 |
red wineWine is an alcoholic beverage typically made of fermented grape juice. The natural chemical balance of grapes is such that they can ferment without the addition of sugars, acids, enzymes or other nutrients. Wine is produced by fermenting crushed grapes using various types of yeast. Yeast consumes...
|
24-35 |
| purple corn |
1,642 |
Anatomically, anthocyanins are found in the cell vacuole, mostly in flowers and
fruitThe term fruit has different meanings dependent on context, and the term is not synonymous in food preparation and biology. Fruits are the means by which flowering plants disseminate seeds, and the presence of seeds indicates that a structure is most likely a fruit, though not all seeds come from...
s but also in
leavesIn botany, a leaf is an above-ground plant organ specialized for photosynthesis. For this purpose, a leaf is typically flat and thin. There is continued debate about whether the flatness of leaves evolved to expose the chloroplasts to more light or to increase the absorption of carbon dioxide. In...
, stems, and
rootIn 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
epidermisThe 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 world. The epidermis serves several functions, it protects against water loss, regulates gas exchange, secretes metabolic compounds, and ...
and peripheral mesophyll cells.
Most frequent in nature are the glycosides of
cyanidinCyanidin is a natural organic compound. It is a particular type of anthocyanidin . It is a pigment found in many redberries including but not limited to grapes, bilberry, blackberry, blueberry, cherry, cranberry, elderberry, hawthorn, loganberry, acai berry and raspberry...
,
delphinidinDelphinidin is an anthocyanidin, a primary plant pigment, and also an antioxidant. Delphinidin gives blue hues to flowers like violas and delphiniums...
,
malvidinMalvidin is an anthocyanidin. As a primary plant pigment, its glycosides are highly abundant in nature. It is primarily responsible for the color of red wine, Vitis vinifera being one of its sources...
,
pelargonidinPelargonidin is an anthocyanidin, or 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...
,
peonidinPeonidin is an 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
petunidinPetunidin is a natural organic compound. It is a particular type of anthocyanidin...
. Roughly 2% of all
hydrocarbonIn organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. With relation to chemical terminology, aromatic hydrocarbons or arenes, alkanes, alkenes and alkyne-based compounds composed entirely of carbon and hydrogen are referred to as "pure"...
s fixated in photosynthesis are converted into flavonoids and their derivatives such as the anthocyanins. There is no less than 10
9 tons of anthocyanins produced in nature per year. Not all land plants contain anthocyanin; in the
CaryophyllalesCaryophyllales is an order of flowering plants that includes the cacti, carnations, amaranths, beets/chard/buckwheat/rhubarb, ice plants, tamarisks and most carnivorous plants. Many members are succulent, having fleshy stems or leaves.-Description:...
(including
cactusA cactus is any member of the plant family Cactaceae, native to the Americas. They are often used as ornamental plants, but some are also crop plants. Cacti are grown for protection of property from wild animals, as well as many other uses...
,
beetThe beet is a plant in the amaranth family. It is best known in its numerous cultivated varieties, the most well known of which is probably the red root vegetable known as the beetroot or garden beet...
s, and
amaranthAmaranthus, collectively known as amaranth or pigweed, 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
betalainBetalains are a class of red and yellow indole-derived pigments found in plants of the Caryophyllales, where they replace anthocyanin pigments, as well as some higher order fungi. They are most often noticeable in the petals of flowers, but may color the fruits, leaves, stems, and roots of plants...
s.
Plants rich in anthocyanins are
VacciniumVaccinium 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
blueberryBlueberries are flowering plants of the genus Vaccinium with dark-blue berries. Species in the section Cyanococcus are the most common fruits sold as "blueberries" and are mainly native to North America. They are usually erect but sometimes prostrate shrubs varying in size from to tall...
,
cranberryCranberries are a group of evergreen dwarf shrubs or trailing vines in the genus Vaccinium subgenus Oxycoccos, or in some treatments, in the distinct genus Oxycoccos...
and
bilberryBilberry is any of several species of low-growing shrubs in the genus Vaccinium , bearing edible fruits. The species most often referred to is Vaccinium myrtillus L., but there are several other closely related species....
,
RubusRubus 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 raspberryBlack raspberry is a common name for two closely related species of the genus Rubus:*Rubus leucodermis, native to western North America*Rubus occidentalis, native to eastern North America...
, red raspberry and
blackberryThe blackberry is an edible berry in the Rubus genus and the Rosaceae family. The fruit are botanically termed an aggregate fruit and they are produced on plants that typically have biennial canes and perennial roots. Blackberries and raspberries are also called caneberries or brambles...
,
blackcurrantThe Blackcurrant is a species of Ribes berry native to central and northern Europe and northern Asia. It is also known as French "cassis"....
,
cherryThe cherry is the fruit of many plants of the genus Prunus. It is a fleshy fruit that contains a single stony seed. The cherry fruits of commerce are usually obtained from a limited number of species, including especially cultivars of the wild cherry, Prunus avium.The name 'cherry', often as the...
, eggplant
peelPeel, 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 riceBlack rice is one of several black-colored heirloom plants producing rice variants such as Indonesian Black Rice, forbidden rice, or wild rice. High in nutritional value, forbidden rice is rich in iron. Unlike other black rice from Asia, it is not glutinous or rough. This grain is high in fiber...
,
Concord grapeConcord grapes are a cultivar derived from the grape species Vitis labrusca which are used as table grapes, wine grapes and juice grapes....
and muscadine grape,
red cabbageThe red cabbage is a sort of cabbage, also known as Red Kraut or Blue Kraut after preparation....
and
violetViola 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
bananaBanana is the common name for a herbaceous plants of the genus Musa, and the commonly eaten fruit it produces. They are native to the tropical region of Southeast Asia, and are likely to have been first domesticated in Papua New Guinea. Today, they are cultivated throughout the tropics.Banana...
,
asparagusAsparagus officinalis is a flowering plant species in the genus Asparagus from which the vegetable known as asparagus is obtained. It is native to most of Europe, northern Africa and western Asia...
,
peaA pea is most commonly the small spherical seed or the seed-pod of the legume Pisum sativum. Each pod contains several peas. Although it is botanically a fruit, it is treated as a vegetable in cooking...
,
fennelFennel , 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...
,
pearThe pear is a tree of genus Pyrus and also the name of the tree's edible pomaceous fruit. The pear is classified within Maloideae, a subfamily within Rosaceae...
and
potatoThe 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. In the region of the Andes, there are some other closely related cultivated potato species. Potatoes are the world's fourth largest food...
, and may be totally absent in certain
cultivarA cultivar is a cultivated plant that has been selected and given a unique name because of desired characteristics; it is usually distinct from similar plants and when propagated it retains those characteristics....
s of green gooseberries.
The highest recorded amount appears to be specifically in the seed coat of black
soybeanThe soybean or soya bean is a species of legume native to East Asia. The plant is classed as an oilseed rather than a pulse. It is an annual plant that has been used in China for 5,000 years to primarily add nitrogen into the soil as part of crop rotation...
(
Glycine max L. Merr.) containing some 2,000 mg per 100 g and in skins and pulp of black
chokeberryThe chokeberries are two 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 compounds, like...
(
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.
Nature, primitive agriculture, and plant breeding have produced various uncommon crops containing anthocyanins, including blue- or red-fleshed 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
tomatoThe tomato is a herbaceous, usually sprawling plant in the Solanaceae or nightshade family that is typically cultivated for the purpose of harvesting its fruit for human consumption...
to transfer a
geneA gene is the basic unit of heredity in a living organism. All living things depend on genes. Genes hold the information to build and maintain their cells and pass genetic traits to offspring...
called the anthocyanin fruit tomato ("aft") gene into a larger and more palatable fruit.
Tomatoes have also been genetically modified with genes from
snapdragonSnapDragon 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. 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 plantOrnamental plants are typically grown in the flower garden or as house plants. Most commonly they are grown for the display of their flowers. Other common ornamental features include leaves, scent, fruit, stem and bark. In some cases, unusual features may be considered ornamental, such as the...
s.
Many science textbooks incompletely state that
autumn colorationAutumn 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 (
carotenoidCarotenoids are organic pigments that are naturally occurring in the chloroplasts and chromoplasts of plants and some other photosynthetic organisms like algae, some types of fungus and some bacteria....
s,
xanthophyllXanthophylls are yellow pigments from the carotenoid group. Their molecular structure is based on carotenes; contrary to the carotenes, some hydrogen atoms are substituted by hydroxyl groups and/or some pairs of hydrogen atoms are substituted by oxygen atoms...
s, and anthocyanins, respectively). While this is indeed the case for the carotenoids and xanthophylls (orange and yellow pigments), anthocyanins are not present until the leaf begins breaking down the chlorophyll, during which time the plant begins to synthesize the anthocyanin, presumably for photoprotection during nitrogen translocation.
Anthocyanidins: Flavylium cation derivatives
See AnthocyanidinAnthocyanidins are common plant pigments. They are the sugar-free counterparts of anthocyanins based on the flavylium ion or 2-phenylchromenylium . They form a large group of polymethine dye. In particular anthocyanidins are salt derivatives of the 2-phenylchromenylium cation, also known as...
s article.
Selected anthocyanidins and their substitutions
| Anthocyanidin |
Basic structure |
R1 |
R2 |
R3 |
R4 |
R5 |
R6 |
R7 |
AurantinidinAurantinidin 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. Aurantiindin has been reported to occur in Impatients aurantiaca , and also in cultivars from genus Alstroemeria....
|
|
−H |
−OH |
−H |
−OH |
−OH |
−OH |
−OH |
| Cyanidin Cyanidin is a natural organic compound. It is a particular type of anthocyanidin . It is a pigment found in many redberries 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 |
DelphinidinDelphinidin 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 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....
|
−OCH3 |
−OH |
−OH |
−OH |
−OCH3 |
−H |
−OH |
| Luteolinidin Luteolinidin is a chemical compound belonging to the 3-deoxyanthocyanidins and that can be found in Sorghum bicolor.-Glycosides:luteolinidin 5-O-�-d-[3-O-�-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 is an anthocyanidin, or 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...
|
−H |
−OH |
−H |
−OH |
−OH |
−H |
−OH |
MalvidinMalvidin is an anthocyanidin. As a primary plant pigment, its glycosides are highly abundant in nature. It is primarily responsible for the color of red wine, Vitis vinifera being one of its sources...
|
−OCH3 |
−OH |
−OCH3 |
−OH |
−OH |
−H |
−OH |
PeonidinPeonidin is an 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 is a natural organic compound. It is a particular type of anthocyanidin...
|
−OH |
−OH |
−OCH3 |
−OH |
−OH |
−H |
−OH |
RosinidinRosinidin is anthocyanidin pigment found in the flowers of Catharanthus roseus and, in lower concentration, in Primula rosea....
|
−OCH3 |
−OH |
−H |
−OH |
−OH |
−H |
−OCH3 |
Anthocyanins: Glucosides of anthocyanidins
The anthocyanins, anthocyanidins with sugar group, are mostly 3-glucosides of the anthocyanidins.
The anthocyanins are subdivided into the
sugarSugar is a class of edible crystalline substances, mainly sucrose, lactose, and fructose. Human taste buds interpret its flavor as sweet. Sugar as a basic food carbohydrate primarily comes from sugar cane and from sugar beet, but also appears in fruit, honey, sorghum, sugar maple , and in many...
-free
anthocyanidinAnthocyanidins are common plant pigments. They are the sugar-free counterparts of anthocyanins based on the flavylium ion or 2-phenylchromenylium . They form a large group of polymethine dye. In particular anthocyanidins are salt derivatives of the 2-phenylchromenylium cation, also known as...
aglyconeAn 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, but is incorrect.- References :...
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
pHpH is a measure of the acidity or basicity of a solution. It is defined as the cologarithm of the activity of dissolved hydrogen ions . Hydrogen ion activity coefficients cannot be measured experimentally, so they are based on theoretical calculations...
indicatorA 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...
, as they change from red in
acidAn acid is traditionally considered any chemical compound that, when dissolved in water, gives a solution with a hydrogen ion activity greater than in pure water, i.e. a pH less than 7.0...
s to blue in
baseIn chemistry, a base is most commonly thought of as an aqueous substance that can accept hydrogen ions. Bases are also the oxides or hydroxides of metals. A soluble base is also often referred to as an alkali if hydroxide ions are involved. This refers to the Brønsted-Lowry theory of acids and bases...
s.
Biosynthesis
- 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 is an α-amino acid with the formula HO
2CCHCH
2C
6H
5. This essential amino acid is classified as nonpolar because of the hydrophobic nature of the benzyl side chain. The codons for
L-phenylalanine are UUU and UUC...
. (see phenylpropanoidPhenylpropanoids are a class of plant-derived organic compounds that are biosynthesized from the amino acid phenylalanine. They have a wide variety of functions, including defense against herbivores, microbial attack, or other sources of injury; as structural components of cell walls; as...
s)
- The other stream produces 3 molecules of 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-CoAAcetyl-CoA is an important molecule in metabolism, used in many biochemical reactions. Its main use 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 between coenzyme A and acetic...
)..
- These streams meet and are coupled together by the enzyme chalcone synthase (CHS), which forms an intermediate chalcone
Chalcone is an aromatic ketone that forms the central core for a variety of important biological compounds, which are known collectively as chalcones. They show antibacterial, antifungal, antitumor and anti-inflammatory properties. Some chalcones demonstrated the ability to block voltage-dependent...
via a polyketidePolyketides are secondary metabolites from bacteria, fungi, plants, and animals. Polyketides are biosynthesized by the polymerization of acetyl and propionyl subunits in a similar process to fatty acid synthesis...
folding mechanism that is commonly found in plants.
- The chalcone is subsequently isomerized by the enzyme chalcone isomerase (CHI) to the prototype pigment naringenin
Naringenin is a 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....
.
- Naringenin is subsequently oxidized by enzymes such as flavanone hydroxylase (FHT or F3H), flavonoid 3' hydroxylase and flavonoid 3' 5'-hydroxylase.
- These oxidation products are further reduced by the enzyme dihydroflavonol 4-reductase (DFR) to the corresponding colorless 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.
- 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.
- The resulting, unstable anthocyanidins are further coupled to sugar molecules by enzymes like UDP-3-O-glucosyl transferase 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.
Potential food value
Anthocyanins are considered
secondary metaboliteSecondary metabolites are organic compounds that are not directly involved in the normal growth, development, or reproduction of organisms. 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 additiveFood additives are substances added to food to preserve flavour or improve 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 numberE numbers are number codes for food additives and are usually found on food labels throughout the European Union. The numbering scheme follows that of the International Numbering System as determined by the Codex Alimentarius committee. Only a subset of the INS additives are approved for use in...
163.
Anthocyanins are powerful antioxidants
in vitroA procedure performed in vitro is performed not in a living organism but in a controlled environment, such as in a test tube or Petri dish...
. This antioxidant property may be conserved even after the plant which produced the anthocyanin is consumed by another organism, possibly explaining why fruits and vegetables with colorful skins and pulp are considered nutritious. Research into the potential range of health benefits from anthocyanins continues.
Dye-sensitized solar cells
Anthocyanins are being used in organic
solar cellA solar cell is a device that converts the energy of sunlight directly into electricity by the photovoltaic effect. Sometimes the term solar cell is reserved for devices intended specifically to capture energy from sunlight, while the term photovoltaic cell is used when the light source is...
s because of their ability to absorb light and convert it into electrons. There are many benefits to using
dye-sensitized solar cellsA dye-sensitized solar cell is a relatively new class of low-cost solar cell, that belong 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 the traditional silicon cells, such as abundance of anthocyanins, the projected 90% efficiency, and the ability to bend or print these inks.
Research
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
Cancer research on anthocyanins is the most advanced, where black
raspberryThe raspberry is the edible fruit of a multitude of plant species in the subgenus Idaeobatus of the genus Rubus; the name also applies to these plants themselves...
(
Rubus occidentalisRubus 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
esophagusThe esophagus or oesophagus , sometimes known as the gullet, is an organ in vertebrates which consists of a muscular tube through which food passes from the pharynx to the stomach. The word esophagus is derived from the Latin œsophagus, which derives from the Greek word oisophagos , lit...
by 30-60% and of the
colonThe colon is the last portion of the digestive system in most vertebrates; it extracts water and salt from solid wastes before they are eliminated from the body....
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
RubusRubus 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
- stalling growth of pre-malignant
Malignancy is the tendency of a medical condition, especially tumors to become progressively worse and to potentially result in death. It is characterized by the properties of anaplasia, invasiveness, and metastasis...
cells
- accelerating the rate of cell turnover, called apoptosis
Apoptosis is the process of programmed cell death that may occur in multicellular organisms. Programmed cell death involves a series of biochemical events leading to a characteristic cell morphology and death; in more specific terms, a series of biochemical events that lead to a variety of...
, effectively making the cancer cells die faster
- reducing inflammatory mediators that initiate tumor onset
- inhibiting growth of new blood vessels that nourish tumors, a process called angiogenesis
Angiogenesis is a physiological process involving the growth of new blood vessels from pre-existing vessels. Though there has been some debate over this, vasculogenesis is the term used for spontaneous blood-vessel formation, and intussusception is the term for new blood vessel formation by...
- minimizing cancer-induced DNA
Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms and some viruses. The main role of DNA molecules is the long-term storage of information...
damage.
On a molecular level, berry anthocyanins were shown to turn off
genesGênes is the name of a département of the First French Empire in present Italy. It was named after the city Genoa. It was formed in 1805, when Napoleon Bonaparte occupied the Republic of Genoa. Its capital was Genoa. It was divided into the arrondissements of Genoa, Bobbio, Novi Ligure, Tortona and...
involved with proliferation,
apoptosisApoptosis is the process of programmed cell death that may occur in multicellular organisms. Programmed cell death involves a series of biochemical events leading to a characteristic cell morphology and death; in more specific terms, a series of biochemical events that lead to a variety of...
, inflammation and angiogenesis.
In 2007, black raspberry studies entered the next pivotal level of research – the human
clinical trialClinical trials are conducted to allow safety and efficacy data to be collected for new drugs or devices. These trials can only take place once satisfactory information has been gathered on the quality of the product and its non-clinical safety, and Health Authority/Ethics Committee approval is...
– for which several approved studies are underway to examine anti-cancer effects of black raspberries and
cranberriesCranberries are a group of evergreen dwarf shrubs or trailing vines in the genus Vaccinium subgenus Oxycoccos, or in some treatments, in the distinct genus Oxycoccos...
on tumors in the esophagus,
prostateThe prostate is a compound tubuloalveolar exocrine gland of the male mammalian reproductive system. Females do not have prostate glands...
and colon.
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
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