Polyphenols, commonly abbreviated as OPC, which in science are defined as oligomeric proanthocyanidins, cannot be produced artificially.
By employing specified bioengineering procedures, such as polymerization, the unnecessary substances are eliminated, thereby retaining the Proanthocyanidins in the remaining material..
Many different extracting techniques are applied by the producers of grape seeds and pine bark. Therefore, the proportion of Proanthocyanidins varies, 
dependant of what technique is employed.
All shares of Proanthocyanidins are identical in their effect, regardless of their origin, which may be grape seeds, cranberries, pine bark or others.
The differences between commercially offered products can be distinctly judged by their particular individual percentage of OPC and by comparing the various additional properties of the raw material having positive effects, such as micro nutrients, trace elements and minerals.
Grape seed extracts contain the highest concentration of proanthocyanidins , in effect 10% more, than can be gained from the bark of pines. Their quality can only be determined by an analysis certification implemented by an independent laboratory. However,, standards for comparative methods are not yet available.
