Pine Bark OPCs (oligomeric proanthocyanidins or OPC'S)

Proanthocyanidins are a class of polyphenols found in a variety of plants. Chemically, they are oligomeric flavonoids. More complex polyphenols, having the same polymeric building block, form the group of tannins. Proanthocyanidins were discovered in 1947 by Jacques Masquelier, who developed and patented techniques for the extraction of oligomeric proanthocyanidins from pine bark and grape seeds
Studies

Oligomeric proanthocyanidin complexes: history, structure, and phytopharmaceutical applications.
http://www.ncbi.nlm.nih.gov/pubmed/19488981

(PDF) Oligomeric Proanthocyanidins (OPCs) - Alternative ...
http://www.altmedrev.com/publications/8/4/442.pdf  (Copy and paste to URL bar)