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Anthocyanin
Anthocyanins are glucosides of anthocyanidins, the basic chemical structure of which is shown here. 
Anthocyanin gives these pansies their dark purple pigmentation. Not to be confused with Anthocyanidin, their sugar free counterparts. Anthocyanins (from Greek: (anthos) = flower + (kyanos) = blue) are water-soluble vacuolar pigments that may appear red, purple, or blue according to pH. They belong to a parent class of molecules called flavonoids synthesized via the phenylpropanoid pathway. Anthocyanins occur in all tissues of higher plants, including leaves, stems, roots, flowers, and fruits. Anthoxanthins are their clear, white to yellow counterparts occurring in plants.
Function
Red color in Fuji apples 
Anthocyanin is the purple color of the vertical stripes on stem of this Jalapeño cultivar. In addition to their role as light-attenuators, anthocyanins also act as powerful antioxidants. 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. Occurrence
Juvenile anthocyanin in new rose growth. The reddish hue disappears as the new leaves mature.
Anatomically, anthocyanins are found in the cell vacuole, mostly in flowers and fruits but also in leaves, stems, and roots. In these parts they are found predominantly in outer cell layers such as the epidermis and peripheral mesophyll cells. Most frequent in nature are the glycosides of cyanidin, delphinidin, malvidin, pelargonidin, peonidin and petunidin. Roughly 2% of all hydrocarbons 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 (including cactus, beets, and amaranth), they are replaced by betalains. Plants rich in anthocyanins are Vaccinium species, such as blueberry, cranberry and bilberry, Rubus berries including black raspberry, red raspberry and blackberry, blackcurrant, cherry, eggplant peel, black rice, Concord grape and muscadine grape, red wine, red cabbage and violet petals. Anthocyanins are less abundant in banana, asparagus, pea, fennel, pear and potato, and may be totally absent in certain cultivars of green gooseberries.[1] The highest recorded amount appears to be specifically in the seed coat of black soybean (Glycine max L. Merr.) containing some 2,000 mg per 100 g[6] and in skins and pulp of black chokeberry (Aronia melanocarpa L.) (table). However, the Amazonian palmberry, açaí, having about 320 mg per 100 g[7] (of which cyanidin-3-glucoside is the most prevalent individual anthocyanin (approximately 10 mg per 100 g),[8] is also a high-content source for which only a small fraction of total anthocyanins has been determined to date. Nature and food science have produced various uncommon crops containing anthocyanins, including blue- or red-fleshed potatoes and purple or red broccoli, cabbage, cauliflower, carrots and corn. Anthocyanins can also be found in naturally ripened olives, and are partly responsible for the purple color seen in Kalamata and Alfonso olives, although no studies to date have have quantified their amount. Autumn leaf color
Plants with abnormally high anthocyanin quantities are popular as ornamental plants - here, a selected purple-leaf cultivar of European Beech StructureAnthocyanidins: Flavylium cation derivativesSee Anthocyanidins article.
Anthocyanins: Glucosides of anthocyanidinsThe anthocyanins, anthocyanidins with sugar group, are mostly 3-glucosides of the anthocyanidins. The anthocyanins are subdivided into the sugar-free anthocyanidin aglycones and the anthocyanin glycosides. As of 2003 more than 400 anthocyanins had been reported[9] 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 indicator, as they change from red in acids to blue in bases. Biosynthesis
Anthocyanins are responsible for the distinctive color of blood oranges, although carotenoids also contribute pigmentation in this fruit.
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 valueAnthocyanins are considered secondary metabolites as a food additive with E number 163. Anthocyanins are powerful antioxidants in vitro. 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. However, it has not yet been scientifically demonstrated that anthocyanins are beneficial to human health. Dye-sensitized solar cellsAnthocyanins are being used in organic solar cells because of their ability to absorb light and convert it into electrons[10]. There are many benefits to using dye-sensitized solar cells instead of the traditional silicon cells, such as abundance of anthocyanins, the projected 90% efficiency, and the ability to bend or print these inks[11]. ResearchRichly 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[12]. Scientists provided laboratory evidence for potential health effects against
Cancer research on anthocyanins is the most advanced, where black raspberry (Rubus occidentalis L.) preparations were first used to inhibit chemically induced cancer of the rat esophagus by 30-60% and of the colon 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 berries[3]. Work on laboratory cancer models has shown that black raspberry anthocyanins inhibit promotion and progression of tumor cells by
On a molecular level, berry anthocyanins were shown to turn off genes involved with proliferation, apoptosis, inflammation and angiogenesis.[13][14][15] In 2007, black raspberry studies entered the next pivotal level of research ? the human clinical trial ? for which several approved studies are underway to examine anti-cancer effects of black raspberries and cranberries on tumors in the esophagus, prostate and colon[16]. References
External links
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