Procyanidins, including the lesser bioactive / bioavailable polymers (4 or more catechines), represent a group of condensed flavan-3-ols that can be found in many plants, most notably apples, maritime pine bark, cinnamon, aronia fruit, cocoa beans, grape seed, grape skin, and red wines of "Vitis vinifera" (the common grape). However, bilberry, cranberry, black currant, green tea, black tea, and other plants also contain these flavonoids, as do cocoa beans. Procyanidins can also 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.