Grape seeds are the primary commercial source of a group of antioxidant, collagen-protective pigments called oligomeric proanthocyanidins (OPCs or PCO), which are concentrated in pine bark and grapes. There are no traditional medicinal uses of OPCs, except to the extent that berries, grapes, and other food sources have been perceived as generally healthful. OPCs restore the antioxidant function of vitamin C molecules worn out by their free radical scavenging activities.