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Oenin is an
Oenin is an anthocyanin
Anthocyanins (), also called anthocyans, are water-soluble vacuolar pigments that, depending on their pH, may appear red, purple, blue, or black. In 1835, the German pharmacist Ludwig Clamor Marquart gave the name Anthokyan to a chemical compo ...
. It is the 3-glucoside
A glucoside is a glycoside that is derived from glucose. Glucosides are common in plants, but rare in animals. Glucose is produced when a glucoside is hydrolysed by purely chemical means, or decomposed by fermentation or enzymes.
The name was o ...
of malvidin
Malvidin is an O-methylated anthocyanidin, the 3',5'-methoxy derivative of delphinidin. As a primary plant pigment, its glycosides are highly abundant in nature.
Natural occurrences
Malvidin is responsible for the blue color found in petals of ...
. It is one of the red pigments found in the skin of purple 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 perhaps 8,000 years ago, ...
s and in wine.
Color stabilization of malvidin 3-glucoside at a higher pH can be explained by self-aggregation of the flavylium cation and copigmentation with the Z-chalcone form. In the presence of procyanidin C2, the red color of oenin appears more stable. However, the HPLC chromatogram shows a decrease in the amplitude of the peaks of oenin and procyanidin C2. Concomitantly, a new peak appears with a maximal absorption in the red region. This newly formed pigment probably comes from the condensation of oenin and procyanidin C2.
Malvidin 3-glucoside alone is not oxidized in the presence of grape polyphenol oxidase
Polyphenol oxidase (PPO; also polyphenol oxidase i, chloroplastic), an enzyme involved in fruit browning, is a tetramer that contains four atoms of copper per molecule.
PPO may accept monophenols and/or ''o''-diphenols as substrates. The ...
, whereas it is degraded in the presence of a crude grape PPO extract and of caftaric acid forming anthocyanidin-caftaric acid adducts.
See also
* Phenolic compounds in wine * Wine color *Malvidin glucoside-ethyl-catechin
Malvidin glucoside-ethyl-catechin is a flavanol-anthocyanin adduct. Flavanol-anthocyanin adducts are formed during wine ageing through reactions between anthocyanins and tannins present in grape, with yeast metabolites such as acetaldehyde. Acetald ...
* Anthocyanone A
Anthocyanone A is a degradation product of malvidin 3-O-glucoside under acidic conditions. It is found in wine
Wine is an alcoholic drink typically made from fermented grapes. Yeast consumes the sugar in the grapes and converts it to eth ...
, a degradation product of oenin found in wine
References
{{Anthocyanins O-methylated anthocyanins