The extract contains proanthocyanidins.[1] Grape seed extract quality is measured by the content of procyanidins which are formed from proanthocyanidins.[2] Generally, grape seed extract quality contains 95% procyanidins, but potency varies among products.[3] Eating foods or beverages high in procyanidin results in the sensation of the mouth puckering and dehydration, otherwise known as astringency, as felt after certain alcoholic drinks.[4]