The compounds known as proanthocyanins are polymers that are also known by a series of other names: flavolans, condensed tannins, polyflavonoid tannins, and proanthocyanidins are only a few examples. Whatever name they are known by, these compounds are the products of the condensation of flavans (a type of flavonoid). As such, proanthocyanins/proanthocyanidins represent yet another subcategory of flavonoids, a class of compounds with a host of beneficial activities that promote optimal health.
A quick look at the health benefits of proanthocyaantioxidant-fruits.comns can be found; among other listed benefits, these compounds increase the effectiveness of vitamin C, prevent heart disease, reduce blood pressure, and promote the formation of collagen. Proanthocyanins have been used to treat a wide variety of ailments, including heart disease and vision impairment. Proanthocyanins also show promise as antioxidants, either due to their in vitro demonstrated antioxidant capabilities or the antioxidant effects of their metabolites; the benefits of antioxidants are, of course, well-known.
Aronia berries and grapes are especially rich sources of proanthocyanins, and offer a good way to start investigating the health benefits of this class of compounds for yourself. You may also be interested to know that red wine is a good source of proanthocyanins, which is likely to be one reason that regular consumption of small quantities of red wine has been so consistently associated with good health.