The primary constituents of Thorne's grape seed extract are oligomeric proanthocyanidins (OPCs). OPCs have strong free-radical scavenging (antioxidant) ability, resulting in inhibition of oxidative damage and protection of blood vessels and other tissues.* OPCs have been shown to protect vascular endothelial cells from oxidative damage and appear to strengthen the resistance of cell membranes to injury and impairment.* OPCs also can bind copper and iron, thereby reducing their oxidative effects.* Grape Seed Extract contains Leucoselect Phytosome®, which have demonstrated in studies to reduce the oxidation of LDL-cholesterol in heavy smokers, and decrease oxidative stress in diabetics and in healthy individuals after a fatty meal.*

Evidence suggests OPCs enhance the cross-linkage of collagen in skin and other connective tissues.* OPCs have also been shown to decrease capillary permeability, which can be manifest as decreased bruising.* For example, clinical studies demonstrate reduced swelling and improved resolution of sports injuries in athletes who were given OPCs prior to a sporting event.*

A clinical study of 10 healthy volunteers analyzing the effect of OPC supplementation on biomarkers of oxidative stress found significantly increased levels of the antioxidant alpha-tocopherol in red blood cell membranes.*

In a randomized human trial, young healthy volunteers received 300 mg of Leucoselect phytosome daily or a placebo. Antioxidant activity was measured at multiple time-points during days one and five. Within 30 minutes after administration on day one, the antioxidant activity measured by "total radical-trapping antioxidant parameter" (TRAP) was significantly elevated compared to placebo.*