Proanthocyanidin (PA or PAC), also known as procyanidin, oligomeric proanthocyanidin (OPC), leukocyanidin, leucoanthocyanin and condensed tannins, is a class of . Proanthocyanidins are essentially chains of such as . One was discovered in 1936 by Professor and called Vitamin P, although this name did not gain official category status and has since fallen out of usage. It was Masquelier who first developed techniques for the extraction of proanthocyanidins from certain plant species.
Proanthocyanidins have been sold as nutritional and therapeutic supplements in Europe since the 1980s, but their introduction to the United States market has been relatively recent.