Grape seed extract contains oligomeric proanthocyanidins (OPCs), which are a type of flavonoid or antioxidant found in many plants. N-acetyl cysteine (NAC) is another powerful antioxidant included in some grape seed extracts and is an altered form of the amino acid cysteine, an alpha-amino acid most proteins have. Keratin, the protein that forms the basis of hair, is abundant in NAC. The proper dosage of grape seed extract is 50mg daily taken with meals and up to 300mg with a doctor’s permission.