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Proanthocyanidins are a class of polyphenols found in a variety of plants. Chemically, they are oligomeric flavonoids. Many are oligomers of catechin and epicatechin and their gallic acid esters. More complex polyphenols, having the same polymeric building block, form the group of tannins. Flavanols are distinguished at the core molecule by the hydroxyl group as opposed to the ketone near same position on the pyran ring in the generally yellow class of flavonoids. Colorless proanthocyanidins are a strictly defined group of 3 flavanols naturally occurring as a mix of monomers, di-mers, and tri-mers of the catechin building block, which is a 4x-hydroxylation of the flavan-3-ol core. Proanthocyanidins were discovered in 1947 by Jacques Masquelier, who developed and patented techniques for the extraction of oligomeric proanthocyanidins from pine bark and grape seeds. == Distribution in plants == Proanthocyanidins, including the lesser bioactive and bioavailable polymers (four or more catechins) represent a group of condensed flavan-3-ols, such as procyanidins, prodelphinidins and propelargonidins, that can be found in many plants, most notably apples, maritime pine bark, cinnamon, aronia fruit, cocoa beans, grape seed, grape skin (procyanidins and prodelphinidins), and red wines of ''Vitis vinifera'' (the European wine grape). However, bilberry, cranberry, black currant, green tea, black tea, and other plants also contain these flavonoids. Cocoa beans contain the highest concentrations.〔 Proanthocyanidins also may be isolated from ''Quercus petraea'' and ''Q. robur'' heartwood (wine barrel oaks). Açaí oil, obtained from the fruit of the açaí palm (''Euterpe oleracea''), is rich in numerous procyanidin oligomers. Apples contain on average per serving about eight times the amount of proanthocyanidin found in wine, with some of the highest amounts found in the Red Delicious and Granny Smith varieties. An extract of maritime pine bark called Pycnogenol bears 65-75 percent proanthocyanidins (procyanidins). Thus a 100 mg serving would contain 65 to 75 mg of proanthocyanidins (procyanidins). Proanthocyanidin glycosides can be isolated from cocoa liquor. The seed testas of field beans (''Vicia faba'') contain proanthocyanidins that affect the digestibility in piglets and could have an inhibitory activity on enzymes. ''Cistus salviifolius'' also contains oligomeric proanthocyanidins. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「proanthocyanidin」の詳細全文を読む スポンサード リンク
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