Clinical OPC 400 mg provides superior absorption for maximum benefits. Oligomeric proanthocyanidins (OPCs) are the powerful health-promoting nutrients in grape seed extract.* Researchers have found that grape seed extract is one of the most promising botanical extracts in the world for a diverse array of health applications. Clinical OPC features French grape seed extract VX1, which is backed by 4 groundbreaking scientific studies and provides a strong ORAC value of 2,103,300 per 100 grams. This unique extract is never adulterated and is standardized for only small size OPCs to better ensure absorption. Clinical OPC Extra Strength supplies only low molecular weight, tannin-free OPCs for high absorbability. Many other grape seed extracts include high levels of tannins—OPCs with a high molecular weight—which have limited absorption and few health benefits.