Phenols (polyphenols) are a group of water-soluble plant dyes with over 6,500 different species. They are found in fruits, flowers and leaves of plants. The flavonoids were discovered in the 1930s by the Nobel Prize winner Albert von Szent-Györgyi Nagyrapolt (1893-1986) and were initially called vitamin P. The name is derived from Latin Flavus (yellow), because flavonoids often, but not always, have a yellow colour. Most flavonoids are bound to the sugar types glucose or rhamnose, which are then called glycosides. The flavonoids are divided into seven groups: anthocyanidins (anthocyans), flavones, flavonols, flavanols, flavanonols and isoflavones.