Grape seed extract is an industrial derivative of whole grape seeds. The extract (GSPE) contains proanthocyanidins. Generally, grape seed extract quality contains 95% procyanidins, but potency varies among products. Eating foods or beverages high in procyanidin results in an astringent sensation in the mouth.
Extraction method
The properties of grape seed extract depend on the extraction process used to obtain it and how the grapes were grown. The classic method incorporates extraction with organic solvents such as acetone, acetonitrile, ethyl acetate, and methanol. Other methods using hot water have been used, but they are not as effective at maximizing extract production in both quantity and efficiency. High performance liquid chromatography seems to be the most effective analysis along with proton NMR spectroscopy with principal component analysis to ensure accurate composition. Oral administration of grape seed extract (dose and frequency unreported) was well tolerated in people over 14 weeks. People with metabolic syndrome had a more significant outcome (average of a 8½ mmHg decrease in systolic blood pressure) than in healthy subjects. There is no clinical evidence that grape seed extract is effective to treat cancer. In 2017, the Food and Drug Administration listed grape seed extract as a fake cancer cure that consumers should avoid.