The main benefit of grape fruit seed extract comes from the chemical compounds called proanthocyanidins. Proanthocyanidins (OPCs) for oligomeric procyanidins (PCOs) for procyanidolic oligomers are a class of nutrients belonging to the flavonoid family.

Proanthocyanidins exhibit antioxidant effects and play a role in the stabilization of collagen and maintenance of elastin used to create connective tissue that is used to support organs, joints, blood vessels, and muscle. Studies have indicated that proanthocyanidins may be useful in reducing the duration of edema after face-lift surgery from almost 16 days to just about 4 days. Other studies have provided preliminary evidence to support the belief that proanthocyanidins can also have anti-mutagenic effects.

Proanthocyanidins have demonstrated some positive effects on vision in healthy people and have shown to possibly prevent and reverse abnormal blood clotting in smokers. (Note: 200 mg was the daily dosage used in vision study)

Proanthocyanidins can be found in many plants, most notably pine bark, grape seed, and grape skin. However, grape seed, cranberry, black currant, green tea, black tea, and other herbs also contain proanthocyanidins. Nutritional supplements containing proanthocyanidins extracts from various plant sources are available alone or in combination with other nutrients in herbal extracts, capsules, and tablets.