Proanthocyanadins are a notable class of flavonoid phyto antioxidants. They are concentrated in the skin of dark colored fruits and also in the bark of some plants, notably pine trees. Proanthocyanadins have potent free radical quenching activity being vigorous neutralizers of even the most potent free radicals such as the hydroxyl radical, superoxide anion, the peroxynitrite radical and excessive nitric oxide. It is likely that this is the reasoning behind red wine showing benefits in preventing heart disease. Proanthocyanadins are also showing very good results in boosting the immune system and in preventing premature ageing of cells.
Mojzisova G & Kuchta M 2001 Physiol Res 50(6): 529
Flesch M et al., 2001 Basic Res Cardiol 96(2): 128