Peonidin
Encyclopedia
Plant
Plants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or...
pigment
Pigment
A pigment is a material that changes the color of reflected or transmitted light as the result of wavelength-selective absorption. This physical process differs from fluorescence, phosphorescence, and other forms of luminescence, in which a material emits light.Many materials selectively absorb...
. Peonidin gives purplish-red hues to flowers such as the peony
Peony
Peony or paeony is a name for plants in the genus Paeonia, the only genus in the flowering plant family Paeoniaceae. They are native to Asia, southern Europe and western North America...
, from which it takes its name, and roses. It is also present in some blue flowers, such as the morning glory
Morning glory
Morning glory is a common name for over 1,000 species of flowering plants in the family Convolvulaceae, whose current taxonomy and systematics is in flux...
.
Like most anthocyanidins it is pH
PH
In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...
sensitive, and changes from red to blue as pH
PH
In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...
rises. This happens because anthocyanidins are highly conjugated chromophores. When the pH is changed, the extent of the conjugation (of the double bonds) is altered, which alters the wavelength of light energy absorbed by the molecule. (Natural anthocyanidins are most stable in a very low pH environment; at pH 8.0, most become colorless.) At pH 2.0, peonidin is cherry red; at 3.0 a strong yellowish pink; at 5.0 it is grape red-purple; and at 8.0 it becomes deep blue; unlike many anthocyanidins, however, it is stable at higher pH, and has in fact been isolated as a blue colorant from the brilliant "Heavenly Blue" morning glory (Ipomoea tricolor Cav cv).
Because of its unusual color stability,a cafeyl-acylated buffered formulation of it has been patented for use as food coloring.
Peonidin, like many anthodcyanidins, has show potent inhibitory and apoptotic effects on cancer cells in vitro, notably metastatic human breast cancer cells.
A very large question, however, has been raised about anthocyanidins' penetration and retention in human cells in vivo, due to their rapid elimination from the human body.
By far the greatest dietary source of peonidin is raw cranberries
Cranberry
Cranberries are a group of evergreen dwarf shrubs or trailing vines in the subgenus Oxycoccus of the genus Vaccinium. In some methods of classification, Oxycoccus is regarded as a genus in its own right...
, which contain 42 mg per 100 g of fruit. Blueberries, plums, grapes, and cherries also contain significant amounts, ranging from 5 to 12 mg/100 g. Only fresh fruit has been shown to contain significant peonidin; frozen blueberries have been shown to contain almost none. It has also been isolated from raw black rice and black bananas.
The higher levels of peonidin in fresh fruit corresponds to the rule of thumb that more natural fruit is healthier. Specifically, the amount of phenolic compounds in cranberries have been found to be inversely correlated with fruit size and crop yield.