To the phenols (Polyphenols) counting group of water-soluble plant dyes with over 6,500 different species. They are contained in fruits, flowers and leaves of plants. The flavonoids were discovered in the 1930s by Nobel laureate Albert von Szent-Györgyi Nagyrapolt (1893-1986) and first as Vitamin P designated. The name derives from Latin Flavus (yellow), because flavonoids often, but not always, have a yellow color. Most flavonoids are due to the sugars glucose or rhamnose, which is then called glycosides be designated. The flavonoids are divided into the seven groups anthocyanidins (anthocyanins), flavones, flavonols, flavanols, flavanones, flavanonols and isoflavones.
Occurring species at grapes are for example the group of anthocyanins ( cyanidin, Delphinidin, malvidine. peonidin, Petunidin), catechin and fisetin in dark (blue to black) grapes, as well quercetin in light (white) grapes. Many flavonoids have a positive effect, as a large part is not absorbed and reaches the large intestine. Due to their antioxidant properties, they have a variety of effects healthy in inflammation, Histamine allergy and convulsions, as well as inhibiting cancer cells and viruses. The second major group of plant colorants found in grapes are the carotenoids (for yellow, green, pink, red).