Proanthocyaniin (also known as procyanidin oligomeric proanthocyanidin (OPC), pycnogenol, leukocyanidin and leucoanthocyanin) is a class of flavanols. Proanthocyanidins are essentially polymer chains of flavinoids such as catechins. One was discovered in 1936 by Professor Jacques Masquelier 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.