Grape seed is rich in flavonoids, phytochemicals that have antioxidant properties. Antioxidants are believed to prevent and control numerous ailments by safeguarding cells against the ravages of unstable oxygen molecules, i.e. the free radicals. Grape seed's anti-oxidative activities are much stronger than vitamin C and vitamin E and may involve radical scavenging, quenching, and enzyme-inhibiting actions.
The most valuable flavonoids in grape seed extract are procyanidolic oligomers (also known as proanthocyanidins). Beyond their antioxidant powers, proanthocyanidins may also help atherosclerosis, gastric ulcer, large bowel cancer, cataracts and diabetes. Thus, grape seed and its extract may benefit people with heart disease and cancer