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The following Executive Summary is part of a White Paper on Grape Seed Extract products that has been issued by the Grape Seed Methods Evaluation Committee.

The Grape Seed Methods Evaluation Committee (GSME) is an ad hoc assemblage of concerned manufacturers, distributors and suppliers who have worked diligently to establish recommended testing and labeling protocols for Grape Seed Extract products. Under the auspices of NNFA, GSME has worked with the natural products industry to bring clarity to the issues of potency and identity for the edification of retailers and consumers. The following recommendations are those of the committee for implementation by the manufacturers and distributors of Grape Seed extract supplements.

Grape Seeds are one of the richest sources of proanthocyanidins; a class of biologically active flavonoids found throughout the plant kingdom. Known for their capacity to act as potent antioxidants, extracts prepared from the seeds of grapes contain a rich mixture of monomeric phenols, phenolic acids and proanthocyanidins. Those compounds consisting of two or more monomers, including polymers and condensed tannins are known collectively as oligomeric proanthocyanidins (OPC’s) by many within the natural products industry. Their structure is composed primarily of catechin, epicatechin, epicatechin gallate, gallic acid esters, glycoside and peptide molecules which can be combined to form a different number of structures. The monomeric group in these extracts are comprised of catechin and epicatechin; with gallic acid present to some extent in almost all extracts used.

Quantifying the oligomeric portion of these compounds has presented a formidable challenge due to the complexity of their structure. Unlike the monomers, which can be easily quantified through accepted analytical methods; the oligomeric proanthocyanidins have perplexed the analytical community for many years. It has been the endeavor of the GSME to find a suitable means for quantifying their presence in grape seed extract products. After three years of investigation, it is the collective opinion of the GSME that the following proposed methods be used for the quantification of OPC’s for purposes of label declarations. This proposal also employs the use of Thin Layer Chromatography (TLC) to identify the material’s origin.

It is the recommendation of GSME that the following methods of analysis be used for purposes of identification and quantification.

• Thin Layer Chromatography (TLC) – Qualitative analysis used to identify the material’s origin i.e. to determine that it originated from a grape source. *

• Modified Folin-Ciocalteu Gallic Acid Equivalent (GAE) – Quantitative Analysis used to determine the percentage of polyphenols as Gallic Acid Equivalents. *
• High Performance Liquid Chromatography (HPLC) – Quantitative analysis used to determine the total amount of polyphenolic monomers including gallic acid, catechin, epicatachin and the gallic acid esters of catechin and epicatechin. *

*For additional testing information, see "Methods of Analysis" section of the Grape Seed White Paper (available upon request through NNFA).

Using the testing protocol recommended by GSME, Grape Seed extract products should be labeled using the following criteria:

• Percentage of total polyphenols
• Percentage of monomers and OPC’s which comprise this total

Example: Grape Seed Extract Powder 100 mg

90 % total polyphenols as Gallic Acid Equivalents (90 mg) containing 85 % Oligomeric Polyphenols (85 mg) and 5% Monomeric Polyphenols (5 mg) (GAE/HPLC) *

* Oligomeric Polyphenols are the total amount of polyphenols as determined by a modified Folin-Ciocalteu (GAE) method of analysis expressed as Gallic Acid Equivalents less the total amount of polyphenolic monomers as determined by HPLC

For additional labeling information, see the Labeling Guide section of the Grape Seed White Paper available through NNFA upon request.