Prasain J.K., Peng N., Dai Y., Moore R., Arabshahi A., Wilson L., Barnes S., Michael Wyss J., Kim H., Watts R.L. (2009) Liquid chromatography tandem mass spectrometry identification of proanthocyanidins in rat plasma after oral administration of grape seed extract. Phytomedicine 16:233-43 PubMed (19095430)

Compound Mean content
(+)-Catechin 65.95 µg/mg dry weight
(-)-Epicatechin 27.4 µg/mg dry weight