Proanthocyanidins-also called "OPCs" for oligomeric proanthocyanidins and "PCOs" for procyanicolic oligomers-are a class of nutrients belonging to the bioflavonoid family. Some researchers also call these molecules "pycnogenol." The main functions of proanthocyanidins are antioxidant activity, stabilization of collagen, and maintenance of elastin-two critical proteins in connective tissue, blood vessels and muscle.

Proanthocyanidins have antioxidant activity and they play a role in the stabilization of collagen and maintenance of elastin—two critical proteins in connective tissue that support organs, joints, blood vessels, and muscle. Possibly because of their effects on blood vessels, proanthocyanidins have been reported in double-blind research to reduce the duration of edema after face-lift surgery from 15.8 to 11.4 days. In preliminary research, proanthocyanidins were reported to have anti-mutagenic activity (i.e., to prevent chromosomal mutations).

The most common antioxidants currently used are vitamin C and vitamin E; however, studies show that proanthocyanidins antioxidant capabilities are 20 times more powerful than vitamin C and 50 times more potent than vitamin E! An important supplement, the proanthocyanidins found in pine bark and grape seed extract work directly to help strengthen all the blood vessels and improve the delivery of oxygen to the cells. Doctor recommended as anti-oxidants, they have become increasingly more important as our environment deteriorates through the introduction of toxins from pollution. Proanthocyanidins also have an affinity for cell membranes, providing nutritional support to reduce capillary permeability and fragility. Although bioflavonoids are widespread in nature, the powerful proanthocyanidin compound is most abundant and available from the bark of the maritime pine and in grape seeds, or pips.

- By inhibiting these enzymes, proanthocyanidins reduce histamine production naturally, eliminating the need for man-made antihistamines and their side-effects; therefore, proanthocyandidins are used in the treatment of allergies.
- Proanthocyanidins help improve circulation. Tissues require a blood supply for their nutrition and for repair purposes in the event of injury. Also, all tissues, whether injured or healthy, produce waste products. These waste products need to be efficiently removed from the tissues. Nutrition is provided by and waste removal is accomplished by capillaries, which are the smallest blood vessels in our body. To do these functions properly, the capillaries must be healthy. Proanthocyanidins strengthen capillary walls, therefore improving circulation. This is especially important for people with compromised circulatory systems, such as stroke victims, diabetics, arthritics, smokers, oral contraceptive users and people with general cardiovascular insufficiencies.
- Proanthocyanidins inhibit the body’s enzymes that break down collagen. All cells connect to one another with strong fibers called collagen. Proanthocyanidins help collagen repair and rebuild correctly which can reverse damage done over the years by injury and free radical attack. The breakdown of collagen is what causes our skin to lose its elasticity which in turn causes wrinkles. Proanthocyanidins help keep skin elastic, smooth and wrinkle-free. Proanthocyanidins are also taken as an oral cosmetic to help in the prevention of wrinkles.
- Proanthocyanidins serve to protect against environmental toxins, such as radiation, pesticides, pollution, heavy metals, etc. The production of free radicals is increased because of today's environment. Tobacco smoke, alcohol, solvents, chemicals and more cause free radicals to form. Since proanthocyanidins eliminate free radicals, they help us fight the toxic effects of our environment.
- Proanthocyanidins act as a natural, internal sunscreen. The Sun's ultraviolet rays destroy up to 50 percent of our skin cells. Proanthocyanidins reduce this amount to approximately 15 percent. Inhibiting the daily effects the Sun's rays have on our skin is our best defense against the aging of our skin.
- Proanthocyanidins cross the blood-brain barrier to protect the blood vessels in the brain.
Unlike most other nutritional supplements, the beneficial effects of proanthocyanidins cross the blood-brain barrier. This enables proanthocyanidins to fight free radicals in the vessels of the brain that in turn will help them remain healthy. This can result in increased mental acuity, a decreased potential for stroke, and possibly in fighting senility.

In summary, proanthocyanidins are a breakthrough in antioxidant protection. They eliminate free radicals that are responsible for as many as 60 diseases, including several conditions associated with aging. Clinical studies have shown that proanthocyanidins are 50 times and 20 times more powerful than vitamin E and vitamin C, respectively. Proanthocyanidins are also vitamin C sparing. This is accomplished by performing many of the same functions as vitamin C and by working synergistically with vitamin C, meaning that proanthocyanidins help vitamin C work better and faster.