Suppression

Anthocyanin

Category: Natural chemicals

Type

Voluntary

Introduction and description

 

Flavonoids are one of the major pigments in higher plants, together with chlorophylls and carotenoids. Though ca. 8,000 kinds of flavonoids have been reported in nature, anthocyanins, chalcones, aurones and some flavonols act as major flower pigments.

Anthocyanins (also anthocyans; from Greek: ἀνθός (anthos) = flower + κυανός (kyanos) = blue) are water-soluble vacuolar pigments that may appear red, purple, or blue.  They are odourless and nearly flavorless, contributing to taste as a moderately astringent sensation. Anthocyanins occur in all tissues of higher plants, including leaves, stems, roots, flowers, and fruits. 

Anthocyanins are derived from anthocyanidins by adding sugars.

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, muscadine grape, 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. Red-fleshed peaches are rich in anthocyanins.

 

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, in purple corn kernels and husks, and in skins and pulp of black chokeberry (Aronia melanocarpa L.) .
Anthocyanins can be used as pH indicators because their colour changes with pH; they are pink in acidic solutions (pH < 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.

Dr Duke’s phytochemical database indicates that anthocyanidins have metal chelating ability [in us].  He lists only one plant because this is the only plant on which this ability has been tested:

Acacia melanoxylon R. BR. -- Blackwood; found in Plant

Furthermore there is no indication of which metal.  But some very tentative evidence has appeared in some somewhat unrelated work on food colours that the chemicals can chelate aluminium:

Use of artificial food colorants has declined due to health concerns and consumer demand, making natural alternatives a high demand. The effects of Al(3+) salt on food source anthocyanins were evaluated with the objective to better understand blue color development of metalloanthocyanins. This is one of the first known studies to evaluate the effects of food source anthocyanin structures, including acylation, with chelation of aluminum. …. Anthocyanin concentration, salt ratio, and pH determined final color and intensity. …This investigation showed anthocyanin-metal chelation can produce a variety of intense violet to blue colors under acidic pH.  PMID:  24547952

Remember that if there is aluminium in the soil, plants with anthocyanins will chelate this too, but their colour is more dependent on the acidity of the growing conditions and not whether they have sucked up masses of aluminium!!

The paper above only gives very weak evidence, but it may be worth pursuing, simply because aluminium is implicated in a number of diseases and the sources of anthocyanins are delicious!!

Anthocyanins are naturally occurring compounds that impart color to fruits, vegetables, and plants. They are probably the most important group of visible plant pigments besides chlorophyll. Apart from imparting color to plants, anthocyanins also have an array of health-promoting benefits, as they can protect against a variety of oxidants through a various number of mechanisms. However, anthocyanins have received less attention than other flavonoids, despite this. This article reviews their biological functions and pre-clinical studies, as well as the most recent analytical techniques concerning anthocyanin isolation and identification.  PMID:  14561507

 

Wikipedia

Due to critical differences in sample origin, preparation and extraction methods determining anthocyanin content, the values presented in the table are not directly comparable.

Food source

Anthocyanin content
in mg per 100 g

Açaí

320

Blackcurrant

190–270

Aronia

1,480

Eggplant

750

Blood orange

~200

Marion blackberry

317

Black raspberry

589

Raspberry

365

Wild blueberry

558

Cherry

350–400

Redcurrant

80–420

Purple corn (Z. mays L.)

1,642

Purple corn leaves

10x more than in kernels

Concord grape

326

Norton grape

888

 Anthocyanins can also be found in naturally ripened olives, and are partly responsible for the red and purple colors of some olives.

References and further reading

  • Krenn, L; Steitz, M; Schlicht, C et al. (November 2007). "Anthocyanin- and proanthocyanidin-rich extracts of berries in food supplements—analysis with problems". Pharmazie 62 (11): 803–12. PMID 18065095.
  • Siriwoharn, T; Wrolstad, RE; Finn, CE; Pereira, CB (December 2004). "Influence of cultivar, maturity, and sampling on blackberry (Rubus L. Hybrids) anthocyanins, polyphenolics, and antioxidant properties". J Agric Food Chem 52 (26): 8021–30 PMID 15612791
  • Wu X, Gu L, Prior RL, McKay S (December 2004). "Characterization of anthocyanins and proanthocyanidins in some cultivars of Ribes, Aronia, and Sambucus and their antioxidant capacity". Journal of Agricultural and Food Chemistry 52 (26): 7846–56. doi:10.1021/jf0486850. PMID 15612766
  • Wada L, Ou B (June 2002). "Antioxidant activity and phenolic content of Oregon caneberries". Journal of Agricultural and Food Chemistry 50 (12): 3495–500. doi:10.1021/jf011405l. PMID 12033817.
  • Hosseinian FS, Beta T (December 2007). "Saskatoon and wild blueberries have higher anthocyanin contents than other Manitoba berries". Journal of Agricultural and Food Chemistry 55 (26): 10832–8. doi:10.1021/jf072529m. PMID 18052240
  • Muñoz-Espada, A. C.; Wood, K. V.; Bordelon, B.; Watkins, B. A. (2004). "Anthocyanin Quantification and Radical Scavenging Capacity of Concord, Norton, and Marechal Foch Grapes and Wines". Journal of Agricultural and Food Chemistry 52 (22): 6779–86. doi:10.1021/jf040087y. PMID 15506816

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