The proanthocyanidins from grape seeds were discovered and patented by the same researcher who discovered pycnogenol in pine bark extract.

Proanthocyanidins have been well studied analytically, biochemically,toxicologically, and clinically. PAC has very powerful antioxidant activity due to the component diphenols and related structures. The proanthocyanidin flavonoids offer an excellent option for adjunct nutritional support of the small vessel circulation. Due to their superior water solubility, they are absorbed well and are generally well tolerated.