Procyanidins are members of the

proanthocyanidin Proanthocyanidins are a class of polyphenols found in many plants, such as cranberry, blueberry, and grape seeds. Chemically, they are oligomeric flavonoids. Many are oligomers of catechin and epicatechin and their gallic acid esters. More compl ...

(or condensed tannins) class of flavonoids. They are oligomeric compounds, formed from

catechin Catechin is a flavan-3-ol, a type of secondary metabolite providing antioxidant roles in plants. It belongs to the subgroup of polyphenols called flavonoids. The name of the catechin chemical family derives from ''catechu'', which is the tanni ...

and

epicatechin Catechin is a flavan-3-ol, a type of secondary metabolite providing antioxidant roles in plants. It belongs to the subgroup of polyphenols called flavonoids. The name of the catechin chemical family derives from ''catechu'', which is the tanni ...

molecules. They yield

cyanidin Cyanidin is a natural organic compound. It is a particular type of anthocyanidin (glycoside version called anthocyanins). It is a pigment found in many red berries including grapes, bilberry, blackberry, blueberry, cherry, chokeberry, cranber ...

when depolymerized under oxidative conditions. See the box below entitled "Types of procyanidins" for links to articles on the various types.

Distribution in plants

Procyanidins, including the lesser bioactive / bioavailable polymers (4 or more catechines), represent a group of condensed flavan-3-ols that can be found in many plants, most notably

apple An apple is an edible fruit produced by an apple tree (''Malus domestica''). Apple trees are cultivated worldwide and are the most widely grown species in the genus ''Malus''. The tree originated in Central Asia, where its wild ancestor, ' ...

maritime pine ''Pinus pinaster'', the maritime pine or cluster pine, is a pine native to the south Atlantic Europe region and parts of the western Mediterranean. It is a hard, fast growing pine bearing small seeds with large wings. Description ''Pinus pinast ...

bark, cinnamon,

aronia ''Aronia'' is a genus of deciduous shrubs, the chokeberries, in the family Rosaceae native to eastern North America and most commonly found in wet woods and swamps. The genus Aronia is considered to have 3 species. The most common and wi ...

fruit,

cocoa bean The cocoa bean (technically cocoa seed) or simply cocoa (), also called the cacao bean (technically cacao seed) or cacao (), is the dried and fully fermented seed of ''Theobroma cacao'', from which cocoa solids (a mixture of nonfat substance ...

s, grape seed, grape skin, and red wines of ''

Vitis vinifera ''Vitis vinifera'', the common grape vine, is a species of flowering plant, native to the Mediterranean region, Central Europe, and southwestern Asia, from Morocco and Portugal north to southern Germany and east to northern Iran. There are curr ...

'' (the common grape). However,

bilberry Bilberries (), or sometimes European blueberries, are a primarily Eurasian species of low-growing shrubs in the genus ''Vaccinium'' (family Ericaceae), bearing edible, dark blue berries. The species most often referred to is '' Vaccinium myrtill ...

cranberry Cranberries are a group of evergreen dwarf shrubs or trailing vines in the subgenus ''Oxycoccus'' of the genus '' Vaccinium''. In Britain, cranberry may refer to the native species '' Vaccinium oxycoccos'', while in North America, cranberry ...

black currant The blackcurrant (''Ribes nigrum''), also known as black currant or cassis, is a deciduous shrub in the family Grossulariaceae grown for its edible berry, berries. It is native species, native to temperate climate, temperate parts of central ...

, green tea,

black tea Black tea, also translated to red tea in various East Asian languages, is a type of tea that is more oxidized than oolong, yellow, white and green teas. Black tea is generally stronger in flavour than other teas. All five types are made from ...

, and other plants also contain these flavonoids.USDA, August 2004
USDA Database for the Proanthocyanidin Content of Selected Foods
PDF summary accessed from main USDA pag

Page accessed July 31, 2015 Procyanidins can also be isolated from ''

Quercus petraea ''Quercus petraea'', commonly known as the sessile oak, Cornish oak, Irish Oak or durmast oak, is a species of oak tree native to most of Europe and into Anatolia and Iran. The sessile oak is the national tree of Ireland, and an unofficial embl ...

'' and '' Q. robur'' heartwood (wine barrel oaks).

Açaí oil Açaí oil is obtained from the fruit of ''Euterpe oleracea'' (açaí palm), which grows in the Amazon rainforest. The oil is rich in phenolic compounds similar in profile to the pulp itself, such as vanillic acid, syringic acid, p-hydroxybenzoi ...

, obtained from the fruit of the

açaí palm The açaí palm (, , from Nheengatu ''asai''), '' Euterpe oleracea,'' is a species of palm tree (Arecaceae) cultivated for its fruit (açaí berries, or simply açaí), hearts of palm (a vegetable), leaves, and trunk wood. Global demand for t ...

(''Euterpe oleracea''), is rich in numerous procyanidin oligomers. 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 Red Delicious is a type of apple with a red exterior and sweet taste that was first recognized in Madison County, Iowa, in 1872. Today, the name ''Red Delicious'' comprises more than 50 cultivars. From 1968 to 2018, it was the most produced cu ...

and

Granny Smith The Granny Smith, also known as a green apple or sour apple, is an apple cultivar which originated in Australia in 1868. It is named after Maria Ann Smith, who propagated the cultivar from a chance seedling. The tree is thought to be a hybrid ...

varieties. The seed testas of field beans (''

Vicia faba ''Vicia faba'', commonly known as the broad bean, fava bean, or faba bean, is a species of vetch, a flowering plant in the pea and bean family Fabaceae. It is widely cultivated as a crop for human consumption, and also as a cover crop. Varieti ...

'') contain procyanidins that affect the digestibility in piglets and could have an inhibitory activity on

enzyme Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products ...

s. '' Cistus salviifolius'' also contains oligomeric procyanidins.

Analysis

Condensed tannins can be characterised by a number of techniques including depolymerisation, asymmetric flow field flow fractionation or small-angle

X-ray scattering X-ray scattering techniques are a family of non-destructive analytical techniques which reveal information about the crystal structure, chemical composition, and physical properties of materials and thin films. These techniques are based on observ ...

. DMACA is a dye used for localization of procyanidin compounds in plant histology. The use of the reagent results in blue staining. It can also be used to titrate procyanidins. Total phenols (or antioxidant effect) can be measured using the Folin-Ciocalteu reaction. Results are typically expressed as

gallic acid Gallic acid (also known as 3,4,5-trihydroxybenzoic acid) is a trihydroxybenzoic acid with the formula C6 H2( OH)3CO2H. It is classified as a phenolic acid. It is found in gallnuts, sumac, witch hazel, tea leaves, oak bark, and other plants. I ...

equivalents (GAE). Procyanidins from field beans (''

'') or

barley Barley (''Hordeum vulgare''), a member of the grass family, is a major cereal grain grown in temperate climates globally. It was one of the first cultivated grains, particularly in Eurasia as early as 10,000 years ago. Globally 70% of barley p ...

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%. An improved colorimetric test, called the ''Porter Assay'' or ''butanol-HCl-iron method'', is the most common PCO assay currently in use. 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.

Gel permeation chromatography Gel permeation chromatography (GPC) is a type of size-exclusion chromatography (SEC), that separates analytes on the basis of size, typically in organic solvents. The technique is often used for the analysis of polymers. As a technique, SEC was fi ...

(GPC) analysis allows to separate monomers from larger PCO molecules. Monomers of procyanidins can be characterized by HPLC analysis. Condensed tannins can undergo acid-catalyzed cleavage in the presence of a nucleophile like

phloroglucinol Phloroglucinol is an organic compound with the formula C6H3(OH)3. It is a colorless solid. It is used in the synthesis of pharmaceuticals and explosives. Phloroglucinol is one of three isomeric benzenetriols. The other two isomers are hydroxyqu ...

(reaction called phloroglucinolysis), thioglycolic acid (thioglycolysis), benzyl mercaptan or cysteamine (processes called

thiolysis Thiolysis is a reaction with a thiol (R-SH) that cleaves one compound into two. Thiolysis involves the addition of coenzyme A to one of the products. This reaction is similar to hydrolysis, which involves water instead of a thiol. This reaction is s ...

) leading to the formation of oligomers that can be further analyzed. Phloroglucinolysis can be used for instance for procyanidins characterisation in wine 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

and

thioglycolate Thioglycolic acid (TGA) is the organic compound HSCH2CO2H. TGA is often called mercaptoacetic acid (MAA). It contains both a thiol (mercaptan) and carboxylic acid functional groups. It is a colorless liquid with a strongly unpleasant odor. TGA is ...

s.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
/ref> Condensed tannins from '' Lithocarpus glaber'' leaves have been analysed through acid-catalyzed degradation in the presence of cysteamine.

Research

Procyanidin content in dietary supplements has not been well documented. Pycnogenol is a dietary supplement derived from extracts from

bark that contains 70% procyanidins, and is marketed with claims it can treat many conditions. The medical evidence is insufficient to support its use for the treatment of seven different chronic disorders.

References

External links

"Pycnogenol: MedlinePlus Supplements"
{{Procyanidin Food chemistry Flavonoid antioxidants de:Oligomere Proanthocyanidine nl:Proanthocyanidine zh:原花色素

Distribution in plants

Analysis

Research

See also

References

External links