Product Code Database
Procyanidins are members of the proanthocyanidin (or ) class of . They are oligomeric compounds, formed from catechin and epicatechin molecules. They yield cyanidin when depolymerized under oxidative conditions.
See the box below entitled "Types of procyanidins" for links to articles on the various types.
Apples contain on average per serving about eight times the amount of procyanidin found in wine, with some of the highest amounts found in the Red Delicious and Granny Smith varieties.
The seed testas of field beans ( Vicia faba) contain procyanidins that affect the digestibility in piglets and could have an inhibitory activity on . Cistus salviifolius also contains oligomeric procyanidins.
Procyanidins from field beans ( Vicia faba) or barley have been estimated using the vanillin-HCl method, resulting in a red color of the test in the presence of catechin or proanthocyanidins.
Procyanidins can be titrated using the Procyanidolic Index (also called the Bates-Smith Assay). It is a testing method that measures the change in color when the product is mixed with certain chemicals. The greater the color changes, the higher the PCOs content is. However, the Procyanidolic Index is a relative value that can measure well over 100. Unfortunately, a Procyanidolic Index of 95 was erroneously taken to mean 95% PCO by some and began appearing on the labels of finished products. All current methods of analysis suggest that the actual PCO content of these products is much lower than 95%. Grape Seed Extract, White paper, The Grape Seed Method Evaluation Committee, Under the Auspices of NNFA ComPli
An improved colorimetric test, called the Porter Assay or butanol-HCl-iron method, is the most common PCO assay currently in use. The Truth About PCOs, Debasis Bagchi, Ph.D. on www.activin.com The unit of measurement of the Porter Assay is the PVU (Porter Value Unit). The Porter Assay is a chemical test to help determine the potency of procyanidin containing compounds, such as grape seed extract. It is an acid hydrolysis, which splits larger chain units (dimers and trimers) into single unit monomers and oxidizes them. This leads to a colour change, which can be measured using a spectrophotometer. The greater the absorbance at a certain wavelength of light, the greater the potency. Ranges for grape seed extract are from 25 PVU for low grade material to over 300 for premium grape seed extracts. Porter Assay on www.omegabiotech.com
Gel permeation chromatography (GPC) analysis allows to separate monomers from larger PCO molecules.
Monomers of procyanidins can be characterized by HPLC analysis. can undergo acid-catalyzed cleavage in the presence of a nucleophile like phloroglucinol (reaction called phloroglucinolysis), thioglycolic acid (thioglycolysis), benzyl mercaptan or cysteamine (processes called thiolysis) leading to the formation of oligomers that can be further analyzed.
Phloroglucinolysis can be used for instance for procyanidins characterisation in wine Analysis of Tannins in Red Wine Using Multiple Methods: Correlation with Perceived Astringency by mean of depolymerisation James A. Kennedy, Jordan Ferrier, James F. Harbertson and Catherine Peyrot des Gachons, Am. J. Enol. Vitic. 57:4, 2006, pp. 481–485 or in the grape seed and skin tissues.
Thioglycolysis can be used to study procyanidins or the oxidation of condensed tannins. It is also used for lignin quantitation. Reaction on condensed tannins from Douglas fir bark produces epicatechin and catechin . Douglas-Fir Bark: Characterization of a Condensed Tannin Extract, by Hong-Keun Song, A thesis submitted to Oregon State University in partial fulfillment of the requirements for the degree of Master of Science, December 13, 1984
Condensed tannins from Lithocarpus glaber leaves have been analysed through acid-catalyzed degradation in the presence of cysteamine.
|
|
