Anthocyanin

In Encyclopedia by Dorothée Delmas Views: 7

The anthocyanins (from Greek anthos “flower” and “dark blue” kuanos) or anthocyanosides (or on the English model anthocyanins) are of natural pigments of leaves, petals and fruit, located in the vacuoles of the cells, soluble in water, ranging from red to blue in the visible spectrum. These are related to an ose (molecule non-ose) heterosides of the anthocyanidins (or anthocyanidols) and thus belong to the class of flavonoids in the broad sense.

Anthocyanins are present in a number of such plants: Blueberry, cherry, ripe, black grape, blood orange, aubergine, potato vitelotte, Plum, Blueberry (Blueberry blue of the Canada, not to be confused with blueberry fields), purple, etc. They give their color as well to autumn leaves to red fruit.

Structure

Anthocyanins are the glycosides of anthocyanidins, i.e. of anthocyanidins with sugar. They are mainly based on five anthocyanidins: cyanidin, delphinidin, peonidin, petunidin and malvidin. Most anthocyanins are 3-glucosides of anthocyanidine.

Their structure derived from the anthocyanidins, anthocyanins are also sensitive to change of changing pH generally red in acid to the basic medium blue, and are therefore also used as colored indicator.

Occurrence

Food	Anthocyanins in mg by 100 g of food
Aronia	200-1000
Eggplant	750
Hawthorne	400
Orange	~ 200
boysen	~ 160
BlackBerry	~ 115
Bilberry	80-420
Cranberry	50-80
loganberry	~ 77
Raspberry	10-60
Cherry	350-400
currant	80-420
red grape	30-750
red wine	24-35
cocoa bean	~
Strawberry	~

Anthocyanins are pigments present only in the vacuole of plants and fungi, but are not found in animals. Indeed, anthocyanin biosynthesis is primarily, as other flavonoids, by the phenylpropanoid pathway. However, all terrestrial plants contain anthocyanin. In the Caryophyllales, cacti and the Galium, they are replaced by the bêtacyanines.

Anthocyanins are mainly fruit but in leaves and roots also. They are mainly located in the outer layers as skin cells. The quantities are large enough: a kilo of blackberries contains for example 1.15 gram, black and Red vegetables contain about 20 mg per gram. Acorns from oak or chestnut fill anthocyanin at germination in spring. About 2% of all hydrocarbons fixed by photosynthesis are converted into flavonoids and their derivatives such as anthocyanins, which is about 10 billion tonnes per year.

Anthocyanins in grapes, concentrated in film. Anthocyanins of the European vine Vitis vinifera are glycosylated only in position 3. Among them, 3 – glucoside of malvidin, purplish color pigment (for example 3 – glucoside of cyanidin is more red) is the most abundant.

Anthocyanins are present with other flavonoids and close chemical compounds such as carotenes and bêtacyanines. They are responsible for the fall color of leaves when photosynthesis is stopped and that chlorophyll has disappeared.

On young plants or new shoots, when chlorophyll production has not yet started and that the plant is therefore without the UV protection, increases the production of anthocyanin. As soon as the production of chlorophyll begins, that of anthocyanins is reduced. The rate of anthocyanins produced depends on the type of plant, the substrate, light and temperature. It was also found that the red colour allows a camouflage against herbivores who are unable to see the red wavelengths. In addition, the anthocyanin synthesis often coincides with the synthesis of unpalatable phenolic compounds to taste.

In 2003, it had more than 400 anthocyanins identified, but studies more recent (early 2006), increased that number to about 550.

Function in plants

Anthocyanins have a protective role for the plant: by absorbing the UV, they would act in shield for DNA and cellular proteins. In addition, colour gives them a role in pollination by the attraction of the species.

Properties

Anthocyanins are characterized by their antioxidant properties favourable to health and particularly against cellular aging by improving the elasticity and the density of the skin. They also avoid redness by strengthening the resistance of the small blood vessels of the skin [REF. necessary].

They allow plants to protect themselves from the UV [REF. necessary]. Because of the differences that appear in their structure in response to a change in pH, and who therefore vary the range of absorbed light, anthocyanins are often used as pH indicator, turning red in acidic, blue base.

Anthocyanin molecules exist in grapes and wine, partly in the form of complexes of different kinds; These complexes appear to play an important role in the intensity and stability of the colour of the wines.

Dieticians often advise eating red fruit so that the organization can benefit from their high content in antioxidants [REF. necessary]. However, the majority of antioxidants and other interesting elements such as vitamins for example, are located in the skin of the fruit [REF. necessary].

Biosynthesis

Anthocyanins are biosynthesized as other flavonoids by the crossing of two tracks metabolic cells plant cell:

• the first part of the shikimate to produce acid amino phenylalanine, which according to the phenylpropanoid pathway will form a derivative paracoumarique acid and coenzyme A, 4 – coumaroyl – CoA
• the second produced three molecules of malonyl-CoA, a unit formed from a C2, the acetyl-CoA unit C3.

• These two routes intersect to form under the action of an enzyme, chalcone synthase, which will form a type intermediate chalcone via a common polyketide folding mechanism in plants.

• Chalcone es then isomerized by the action of an enzyme, chalcone isomerase (CHI) which causes Cyclization internal forming a flavonoid, specifically a flavanone, such as for example the naringenin.

• The flavanone is then oxidized by the enzyme type flavanone hydroxylase (FHT or F3H), flavonoid 3′hydroxylase and flavonoid 3′ 5′-hydroxylase.

• The product of this oxidation is then reduced by the action of the enzyme dihydroflavonol 4-reductase (DFR) in leucoanthocyanidin, colourless, corresponding.

• It was long thought that the leucoanthocyanidines were the direct precursors of the anthocyanidins, by the action of an enzyme dioxygenase called anthocyanidine synthase (years) or leucoanthocyanidin dioxygenase (LDOX). It has been recently shown that in fact it is the flavan-3-ols, the products of the action on the leucoanthocyanidin of leucoanthocyanidin reductase (LAR), which are the real reactants producing the anthocyanidins under the actions of the years/LDOX.

• The product of this reaction, a generally unstable anthocyanidine, is then coupled to an ESO by type UDP-3-O-glucosyltransferase enzyme to form a Glycoside, anthocyanin, relatively stable.