Anthocyanidins are common plant pigments, the

aglycone An aglycone (aglycon or genin) is the chemical compound remaining after the glycosyl group on a glycoside is replaced by a hydrogen atom. For example, the aglycone of a cardiac glycoside would be a steroid A steroid is an organic compoun ...

s of

anthocyanin Anthocyanins (), also called anthocyans, are solubility, water-soluble vacuole, vacuolar pigments that, depending on their pH, may appear red, purple, blue, or black. In 1835, the German pharmacist Ludwig Clamor Marquart named a chemical compou ...

s. They are based on the flavylium

cation An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...

, an

oxonium ion In chemistry, an oxonium ion is any cation containing an oxygen atom that has three chemical bond, bonds and 1+ formal charge. The simplest oxonium ion is the hydronium ion (). Alkyloxonium Hydronium is one of a series of oxonium ions with the fo ...

, with various groups substituted for its

hydrogen Hydrogen is a chemical element; it has chemical symbol, symbol H and atomic number 1. It is the lightest and abundance of the chemical elements, most abundant chemical element in the universe, constituting about 75% of all baryon, normal matter ...

atoms. They generally change color from red through purple, blue, and bluish green as a function of pH. Anthocyanidins are an important subclass of the polymethine dyes and

flavonoid Flavonoids (or bioflavonoids; from the Latin word ''flavus'', meaning yellow, their color in nature) are a class of polyphenolic secondary metabolites found in plants, and thus commonly consumed in the diets of humans. Chemically, flavonoids ...

s. The flavylium cation is a chromenylium cation with a

phenyl In organic chemistry, the phenyl group, or phenyl ring, is a cyclic group of atoms with the formula , and is often represented by the symbol Ph (archaically φ) or Ø. The phenyl group is closely related to benzene and can be viewed as a benzene ...

group substituted in position 2; and chromenylium (also called benzopyrylium) is a bicyclic version of pyrylium. The positive charge can move around the molecule. At least 31 monomeric anthocyanidins have been properly identified in living organisms, mostly as the core components of anthocyanins. The latter are responsible for the red, purple, blue, or black color of many fruits (like

grape A grape is a fruit, botanically a berry, of the deciduous woody vines of the flowering plant genus ''Vitis''. Grapes are a non- climacteric type of fruit, generally occurring in clusters. The cultivation of grapes began approximately 8,0 ...

s and

blueberries Blueberries are a widely distributed and widespread group of perennial flowering plants with blue or purple berries. They are classified in the section ''Cyanococcus'' with the genus ''Vaccinium''. Commercial blueberries—both wild (lowbush) ...

), flowers (like

rose A rose is either a woody perennial plant, perennial flowering plant of the genus ''Rosa'' (), in the family Rosaceae (), or the flower it bears. There are over three hundred Rose species, species and Garden roses, tens of thousands of cultivar ...

s), leaves (like purple cabbage), and even tubers (like

radish The radish (''Raphanus sativus'') is a flowering plant in the mustard family, Brassicaceae. Its large taproot is commonly used as a root vegetable, although the entire plant is edible and its leaves are sometimes used as a leaf vegetable. Origina ...

es and purple yams). They are also found in some animals.

Classification

3-Deoxyanthocyanidin The 3-Deoxyanthocyanidins and their glycosides (3-deoxyanthocyanins or 3-DA) are molecules with an anthocyanidins backbone lacking an hydroxyl group at position 3 on the C-ring. This nomenclature is the inverse of that which is commonly used in ...

s such as

luteolinidin Luteolinidin is a member of the 3-deoxyanthocyanidins. It is an orange pigment, found e.g. in ''Sorghum bicolor ''Sorghum bicolor'', commonly called sorghum () and also known as great millet, broomcorn, guinea corn, durra, imphee, jowar, o ...

are a class of anthocyanidins lacking an hydroxyl group on carbon 3. :

Natural occurrence

Most plant anthocyanins are based on cyanidin (30%), delphinidin (22%), and pelargonidin (18%), respectively. Altogether 20% of the anthocyanins are based on the three common anthocyanidins (peonidin, malvidin, and petunidin) that are methylated. Around 3%, 3%, and 2% of the anthocyanins or anthocyanidins are respectively labeled as 3-desoxyanthocyanidins, rare methylated anthocyanidins, and 6-hydroxyanthocyanidins, respectively. In bryophytes, anthocyanins are usually based on 3-desoxyanthocyanidins located in the cell wall. A new anthocyanidin, riccionidin A, has been isolated from the liverwort '' Ricciocarpos natans''. It could be derived from 6,7,2′,4′,6′-pentahydroxyflavylium, having undergone ring closure of the 6’ -hydroxyl at the 3-position. Its visible spectrum in

methanol Methanol (also called methyl alcohol and wood spirit, amongst other names) is an organic chemical compound and the simplest aliphatic Alcohol (chemistry), alcohol, with the chemical formula (a methyl group linked to a hydroxyl group, often ab ...

ic HCl is at 494 nm. This pigment was accompanied by riccionidin B, which most probably is based on two molecules of riccionidin A linked via the 3′- or 5′-positions. Both pigments were also detected in the liverworts ''Marchantia polymorpha'', ''Riccia duplex'', and ''Scapania undulata''.

Effect of pH

The stability of anthocyanidins is dependent on pH. At a low pH (acidic conditions), colored anthocyanidins are present, whereas at a higher pH (basic conditions) the colorless chalcones forms are present. Cyanidin - Farbstoff pH-Abhaengigkeit

References

External links

* {{Authority control PH indicators Bioindicators