Procyanidin

Epicatechin (EC), one of the building blocks of procyanidins
Cyanidin, the anthocyanidin produced when procyanidin are depolymerized under oxidative conditions

Procyanidins are members of the proanthocyanidin (or condensed tannins) class of flavonoids. They are oligomeric compounds, formed from catechin and epicatechin molecules. They yield cyanidin when depolymerized under oxidative conditions.

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 apples, maritime pine bark, cinnamon, aronia fruit, cocoa beans, grape seed, grape skin,[1] and red wines of Vitis vinifera (the common grape). However, bilberry, cranberry, black currant, green tea, black tea, and other plants also contain these flavonoids. Cocoa beans contain the highest concentrations.[2] Procyanidins can also be isolated from Quercus petraea and Q. robur heartwood (wine barrel oaks).[3] Açaí oil, obtained from the fruit of the açaí palm (Euterpe oleracea), is rich in numerous procyanidin oligomers.[4]

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.[5]

A patented extract of maritime pine bark called Pycnogenol bears 65-75 percent procyanidins (procyanidins).[6] Thus a 100 mg serving would contain 65 to 75 mg of procyanidins.

The seed testas of field beans (Vicia faba) contain procyanidins[7] that affect the digestibility in piglets[8] and could have an inhibitory activity on enzymes.[9] Cistus salviifolius also contains oligomeric procyanidins.[10]

Analysis

Condensed tannins can be characterised by a number of techniques including depolymerisation, asymmetric flow field flow fractionation or small-angle X-ray scattering.[4]

DMACA is a dye that is particularly useful for localization of procyanidin compounds in plant histology. The use of the reagent results in blue staining.[11] 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 equivalents (GAE).

Procyanidins from field beans (Vicia faba)[12] or barley[13] have been estimated using the vanillin-HCl method, resulting in a red color of the test in the presence of catechin or proanthcyanidins.

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%.[14]

An improved colorimetric test, called the Porter Assay or butanol-HCl-iron method, is the most common PCO assay currently in use.[15] 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.[16]

Gel permeation chromatography (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 (reaction called phloroglucinolysis), thioglycolic acid (thioglycolysis), benzyl mercaptan or cysteamine (processes called thiolysis[17]) leading to the formation of oligomers that can be further analyzed.[18]

Uses

This information attracted the attention of public news media, describing that red wine consumption is associated with favorable intake of health-promoting flavonoids that correlate positively with oxygen radical absorbance capacity (ORAC).

In red wines, total oligomeric procyanidin content, including flavan-3-ols (catechins), was substantially higher (177.18 ± 96.06 mg/L) than that in white wines (8.75 ± 4.53 mg/L). A relative high correlation in red wines was found between ORAC values and malvidin compounds (r = 0.75, P < 0.10), and procyanidins (r = 0.87, P < 0.05).[19]

In white wines, a significant correlation was found between the trimeric procyanidin fraction and peroxyl radical scavenging values (r = 0.86, P < 0.10).

A moderate drink (1 drink per day, about 140 mL) of red wine, or white wine, or wine made from highbush blueberry corresponded to an intake of 2.04 ± 0.81 mmol of TE (Trolox equivalents), 0.47 ± 0.15 mmol of TE, and 2.42 ± 0.88 mmol of TE of ORAC/day, respectively.[19][20]

Procyanidins are the principal vasoactive polyphenols in red wine that are linked to a reduced risk of coronary heart disease and to lower overall mortality.[21] Procyanidins are present at higher concentrations in wines from areas of southwestern France and Sardinia, which are associated with increased longevity in the population. Earlier studies that attributed this health benefit to resveratrol were premature because of the negligible amount of resveratrol in red wine.

Procyanidins suppress production of a protein endothelin-1 that constricts blood vessels.[21]

These studies provide data supporting the French Paradox that hypothesizes that intake of procyanidins and other flavonoids from regular consumption of red wines prevents occurrence of a higher disease rate (cardiovascular diseases, diabetes) in French citizens on high-fat diets.[21]

Procyanidins have antioxidant activity and they play a role in the stabilization of collagen and maintenance of elastin — two critical proteins in connective tissue that support organs, joints, blood vessels, and muscle. Possibly because of their effects on blood vessels, procyanidins have been reported in double-blind research to reduce the duration of edema after face-lift surgery from 15.9 to 11.5 days. In preliminary research, procyanidins were reported to have anti-mutagenic activity (i.e., to prevent chromosomal mutations).

Common antioxidants currently used are vitamin C and vitamin E; however, studies show that procyanidins antioxidant capabilities are 20 times more powerful than vitamin C and 50 times more potent than vitamin E.[22] Procyanidins found in French maritime pine bark and grape seed extract work directly to help strengthen all the blood vessels and improve the delivery of oxygen to the cells. Procyanidins also have an affinity for cell membranes, providing nutritional support to reduce capillary permeability and fragility. Although flavonoids are widespread in nature, the powerful procyanidin compounds are most abundant and available from the bark of the maritime pine and in grape seeds, or pips. In addition, the particular procyanidins found in the proprietary extract of maritime pine bark called Pycnogenol have been shown to optimize the production of nitric oxide in the artery walls so as to relax them and allow greater blood flow and reduced pressure.[23] Additionally, this same preparation, Pycnogenol, has been found to normalize platelet adhesion (aggregation) so as to facilitate normal blood flow.[24] Nevertheless, meta-analysis of clinical studies on Pycnogenol(®) published in 2012 concluded:

"Current evidence is insufficient to support Pycnogenol(®) use for the treatment of any chronic disorder. Well-designed, adequately powered trials are needed to establish the value of this treatment."[25]

Oligomeric proanthocyanidins

In 1947 Jack Masquelier discovered oligomeric proanthocyanidins (OPCs) in the skin of a peanut by accident. Oligomeric proanthocyanidins strictly refer to di-mer and tri-mer polymerizations of catechins (see above). OPCs are found in most plants and thus are a part of the human diet. Especially the skin, seeds and seed coverings of plants contain large amounts of oligomeric proanthocyanidins. They can be found in large quantities in grape seed extract and skin, in red grapes, in the red skins of peanuts, in coconuts, apples (dimeric procyanidin B2), in cocoa, and in the bark of Pinus pinaster (formerly known as Pinus maritima). It can also be found in sea buckthorn oil.[26]

Oligomeric proanthocyanidins can be obtained by the mean of Vaccinium pahalae in vitro cell culture.[27]

Biological signifiance

In nature, it is possible that PCOs serve as a plant defense against herbivory.

Research

Procyanidins have antioxidant properties in vitro. Foods rich in procyanidins have high oxygen radical absorbance capacity, an in vitro measure with unproven relationship to antioxidant effects in vivo.[28] Scientists continue to research the relevance of antioxidant properties in vitro and potential effects of PCOs on cancer or cardiovascular disease as determined in laboratory studies.[29] USDA does maintain a database of procyanidin content and structure for many foods, but procyanidin content in dietary supplements has not been well documented.[30]

In one preliminary human study, cocoa procyanidins may have influenced platelet function.[31] In one study on mice, procyanidins may have had antidepressant effects and MAO inhibitory properties.[32]

A French maritime pine bark extract of PCOs, pycnogenol, might affect microcirculation, retinal edema and visual acuity, according to one study.[33] Further preliminary research indicated that pycnogenol may have anti-inflammatory properties, may bind to collagen and elastin, or may be involved in production of endothelial nitric oxide.[34] Pycnogenol is under study for its possible influence on blood glucose (sugar) levels.[35][36]

Sources

PCOs are present in fresh grapes, grape juice, and red wine. Although red wine may contain more PCOs than red grape juice, red grape juice contains more PCOs per average serving size. An 8-ounce serving of grape juice averages 124 milligrams PCOs, whereas a 5-ounce serving of red wine averages 91 milligrams.[2][37] Many other foods and beverages may also contain PCOs, but few attain the levels found in red grape seeds and skins.[2]

Chemical depolymerisation

The condensed tannins can nevertheless undergo acid-catalyzed cleavage in the presence of (an excess of) a nucleophile[38] like phloroglucinol (reaction called phloroglucinolysis), benzyl mercaptan (reaction called thiolysis), thioglycolic acid (reaction called thioglycolysis) or cysteamine. These techniques are generally called depolymerisation and give informations such as average degree of polymerisation or percentage of galloylation. These are SN1 reactions, a type of substitution reaction in organic chemistry, involving a carbocation intermediate under strongly acidic conditions in polar protic solvents like methanol. The reaction leads to the formation of free and derived monomers that can be further analyzed. The free monomers correspond to the terminal units of the condensed tannins chains.

In general, reactions are made in methanol, especially thiolysis, as benzyl mercaptan has a low solubility in water. They involve a moderate (50 to 90°C) heating for a few minutes. Epimerisation may happen.

Phloroglucinolysis can be used for instance for procyanidins characterisation in wine[39] or in the grape seed and skin tissues.[40]

Thioglycolysis can be used to study procyanidins[41] or the oxidation of condensed tannins.[42] It is also used for lignin quantitation.[43] Reaction on condensed tannins from Douglas fir bark produces epicatechin and catechin thioglycolates.[44]

Condensed tannins from Lithocarpus glaber leaves have been analysed through acid-catalyzed degradation in the presence of cysteamine.[45]

See also

References

  1. ↑ Souquet, J; Cheynier, Véronique; Brossaud, Franck; Moutounet, Michel (1996). "Polymeric proanthocyanidins from grape skins". Phytochemistry 43 (2): 509. doi:10.1016/0031-9422(96)00301-9.
  2. ↑ 2.0 2.1 2.2 USDA Database for the Proanthocyanidin Content of Selected Foods – 2004 <http://www.ars.usda.gov/Services/docs.htm?docid=5843>
  3. ↑ Vivas, N; Nonier, M; Pianet, I; Vivasdegaulejac, N; Fouquet, E (2006). "Proanthocyanidins from Quercus petraea and Q. robur heartwood: quantification and structures". Comptes Rendus Chimie 9: 120. doi:10.1016/j.crci.2005.09.001.
  4. ↑ Pacheco-Palencia LA, Mertens-Talcott S, Talcott ST (Jun 2008). "Chemical composition, antioxidant properties, and thermal stability of a phytochemical enriched oil from Acai (Euterpe oleracea Mart.)". J Agric Food Chem 56 (12): 4631–6. doi:10.1021/jf800161u. PMID 18522407.
  5. ↑ Hammerstone, John F.; Lazarus, Sheryl A.; Schmitz, Harold H. (August 2000). "Procyanidin content and variation in some commonly consumed foods". The Journal of nutrition 130 (8S Suppl): 2086S–92S. PMID 10917927. Figure 5
  6. ↑ Rohdewald, P (2002). "A review of the French maritime pine bark extract (Pycnogenol), a herbal medication with a diverse clinical pharmacology". International journal of clinical pharmacology and therapeutics 40 (4): 158–68. doi:10.5414/cpp40158. PMID 11996210.
  7. ↑ Merghem, R.; Jay, M.; Brun, N.; Voirin, B. (2004). "Qualitative analysis and HPLC isolation and identification of procyanidins fromvicia faba". Phytochemical Analysis 15 (2): 95–99. doi:10.1002/pca.731. PMID 15116939.
  8. ↑ Van Der Poel, A. F. B.; Dellaert, L. M. W.; Van Norel, A.; Helsper, J. P. F. G. (2007). "The digestibility in piglets of faba bean (Vicia faba L.) as affected by breeding towards the absence of condensed tannins". British Journal of Nutrition 68 (3): 793. doi:10.1079/BJN19920134.
  9. ↑ Griffiths, D. W. (1981). "The polyphenolic content and enzyme inhibitory activity of testas from bean (Vicia faba) and pea (Pisum spp.) varieties". Journal of the Science of Food and Agriculture 32 (8): 797. doi:10.1002/jsfa.2740320808.
  10. ↑ Qa’Dan, F.; Petereit, F.; Mansoor, K.; Nahrstedt, A. (2006). "Antioxidant oligomeric proanthocyanidins fromCistus salvifolius". Natural Product Research 20 (13): 1216–1224. doi:10.1080/14786410600899225. PMID 17127512.
  11. ↑ Bogs, J.; Jaffe, F. W.; Takos, A. M.; Walker, A. R.; Robinson, S. P. (2007). "The Grapevine Transcription Factor VvMYBPA1 Regulates Proanthocyanidin Synthesis during Fruit Development". Plant Physiology 143 (3): 1347–61. doi:10.1104/pp.106.093203. PMC 1820911. PMID 17208963.
  12. ↑ Cabrera, A.; Martin, A. (2009). "Genetics of tannin content and its relationship with flower and testa colours in Vicia faba". The Journal of Agricultural Science 113: 93. doi:10.1017/S0021859600084665.
  13. ↑ Kristensen, H.; Aastrup, S. (1986). "A non-destructive screening method for proanthocyanidin-free barley mutants". Carlsberg Research Communications 51 (7): 509. doi:10.1007/BF02906893.
  14. ↑ Grape Seed Extract, White paper, The Grape Seed Method Evaluation Committee, Under the Auspices of NNFA ComPli
  15. ↑ The Truth About PCOs, Debasis Bagchi, Ph.D. on www.activin.com
  16. ↑ Porter Assay on www.omegabiotech.com
  17. ↑ Torres, J. L.; Lozano, C. (2001). "Chromatographic characterization of proanthocyanidins after thiolysis with cysteamine". Chromatographia 54 (7–8): 523. doi:10.1007/BF02491211.
  18. ↑ Jorgensen, Emily M.; Marin, Anna B.; Kennedy, James A. (2004). "Analysis of the Oxidative Degradation of Proanthocyanidins under Basic Conditions". Journal of Agricultural and Food Chemistry 52 (8): 2292–6. doi:10.1021/jf035311i. PMID 15080635.
  19. ↑ 19.0 19.1 Sánchez-Moreno, Concepción; Cao, Guohua; Ou, Boxin; Prior, Ronald L. (2003). "Anthocyanin and Proanthocyanidin Content in Selected White and Red Wines. Oxygen Radical Absorbance Capacity Comparison with Nontraditional Wines Obtained from Highbush Blueberry". Journal of Agricultural and Food Chemistry 51 (17): 4889–96. doi:10.1021/jf030081t. PMID 12903941.
  20. ↑ ":: Blueberries ::". Blueberry.org. Retrieved 2011-05-23.
  21. ↑ 21.0 21.1 21.2 Corder, R.; Mullen, W.; Khan, N. Q.; Marks, S. C.; Wood, E. G.; Carrier, M. J.; Crozier, A. (2006). "Oenology: Red wine procyanidins and vascular health". Nature 444 (7119): 566. doi:10.1038/444566a. PMID 17136085.
  22. ↑ Shi, John; Yu, Jianmel; Pohorly, Joseph E.; Kakuda, Yukio (2003). "Polyphenolics in Grape SeedsBiochemistry and Functionality". Journal of Medicinal Food 6 (4): 291–9. doi:10.1089/109662003772519831. PMID 14977436.
  23. ↑ Nishioka, Kenji; Hidaka, Takayuki; Nakamura, Shuji; Umemura, Takashi; Jitsuiki, Daisuke; Soga, Junko; Goto, Chikara; Chayama, Kazuaki et al. (2007). "Pycnogenol, French Maritime Pine Bark Extract, Augments Endothelium-Dependent Vasodilation in Humans". Hypertension Research 30 (9): 775–80. doi:10.1291/hypres.30.775. PMID 18037769.
  24. ↑ Pütter, M; Grotemeyer, KH; Würthwein, G; Araghi-Niknam, M; Watson, RR; Hosseini, S; Rohdewald, P (1999). "Inhibition of smoking-induced platelet aggregation by aspirin and pycnogenol". Thrombosis research 95 (4): 155–61. doi:10.1016/S0049-3848(99)00030-4. PMID 10498385.
  25. ↑ Schoonees, A; Visser, J; Musekiwa, A; Volmink, J (2012). Volmink, Jimmy, ed. "Pycnogenol(®) for the treatment of chronic disorders". Cochrane Database Syst Rev. 2012 (2): 008294. doi:10.1002/14651858.CD008294.pub3. PMID 22336841.
  26. ↑ Rösch, Daniel; Mügge, Clemens; Fogliano, Vincenzo; Kroh, Lothar W. (2004). "Antioxidant Oligomeric Proanthocyanidins from Sea Buckthorn (Hippophaë rhamnoides) Pomace". Journal of Agricultural and Food Chemistry 52 (22): 6712–8. doi:10.1021/jf040241g. PMID 15506806.
  27. ↑ Kandil, F. E.; Song, L.; Pezzuto, J. M.; Marley, K.; Seigler, D. S.; Smith, M. A. L. (2000). "Isolation of oligomeric proanthocyanidins from flavonoid-producing cell cultures". In Vitro Cellular & Developmental Biology - Plant 36 (6): 492. doi:10.1007/s11627-000-0088-1.
  28. ↑ Oxygen Radical Absorbance Capacity (ORAC) of Selected Foods – 2007 (PDF). November 2007.
  29. ↑ Cos, P; De Bruyne, T; Hermans, N; Apers, S; Berghe, DV; Vlietinck, AJ (2004). "Proanthocyanidins in health care: current and new trends". Current medicinal chemistry 11 (10): 1345–59. doi:10.2174/0929867043365288. PMID 15134524.
  30. ↑ USDA Database for the Proanthocyanidin Content of Selected Foods (PDF). August 2004.
  31. ↑ Murphy, Karen J.; Chronopoulos, Andriana K.; Singh, Indu; Francis, Maureen A.; Moriarty, Helen; Pike, Marilyn J.; Turner, Alan H.; Mann, Neil J.; Sinclair, Andrew J. (June 2003). "Dietary flavanols and procyanidin oligomers from cocoa (Theobroma cacao) inhibit platelet function". Am J Clin Nutr 77 (6): 1466–73. PMID 12791625.
  32. ↑ Xu Y; Li S; Chen R et al. (January 2010). "Antidepressant-like effect of low molecular proanthocyanidin in mice: involvement of monoaminergic system". Pharmacol. Biochem. Behav. 94 (3): 447–53. doi:10.1016/j.pbb.2009.10.007. PMID 19857512.
  33. ↑ Steigerwalt, Robert; Belcaro, Gianni; Cesarone, Maria Rosaria; Di Renzo, Andrea; Grossi, Maria Giovanna; Ricci, Andrea; Dugall, Mark; Cacchio, Marisa; Schönlau, Frank (2009). "Pycnogenol Improves Microcirculation, Retinal Edema, and Visual Acuity in Early Diabetic Retinopathy". Journal of Ocular Pharmacology and Therapeutics 25 (6): 537–540. doi:10.1089/jop.2009.0023. PMID 19916788. Lay summary – Horphag Research (December 2, 2009).
  34. ↑ "Antioxidant May Help Lower Blood Pressure".
  35. ↑ Liu, Ximing; Zhou, Ha-Jun; Rohdewald, Peter (2004). "French Maritime Pine Bark Extract Pycnogenol Dose-Dependently Lowers Glucose in Type 2 Diabetic Patients". Diabetes Care 27 (3): 839. doi:10.2337/diacare.27.3.839.
  36. ↑ Schäfer, Angelika; Högger, Petra (2007). "Oligomeric procyanidins of French maritime pine bark extract (Pycnogenol) effectively inhibit α-glucosidase". Diabetes Research and Clinical Practice 77 (1): 41–6. doi:10.1016/j.diabres.2006.10.011. PMID 17098323.
  37. ↑ Grape Juice Beats Wine in New Antioxidant Tests <http://www.medicalnewstoday.com/medicalnews.php?newsid=15553>
  38. ↑ Matthews, S.; Mila, I.; Scalbert, A.; Pollet, B.; Lapierre, C.; Hervé Du Penhoat, C. L. M.; Rolando, C.; Donnelly, D. M. X. (1997). "Method for Estimation of Proanthocyanidins Based on Their Acid Depolymerization in the Presence of Nucleophiles". Journal of Agricultural and Food Chemistry 45 (4): 1195. doi:10.1021/jf9607573.
  39. ↑ 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
  40. ↑ Kennedy, J. A.; Jones, G. P. (2001). "Analysis of Proanthocyanidin Cleavage Products Following Acid-Catalysis in the Presence of Excess Phloroglucinol". Journal of Agricultural and Food Chemistry 49 (4): 1740–1746. doi:10.1021/jf001030o. PMID 11308320.
  41. ↑ Sears, K. D.; Casebier, R. L. (1968). "Cleavage of proanthocyanidins with thioglycollic acid". Chemical Communications (London) (22): 1437. doi:10.1039/C19680001437.
  42. ↑ Vernhet, A.; Dubascoux, S. P.; Cabane, B.; Fulcrand, H. L. N.; Dubreucq, E.; Poncet-Legrand, C. L. (2011). "Characterization of oxidized tannins: Comparison of depolymerization methods, asymmetric flow field-flow fractionation and small-angle X-ray scattering". Analytical and Bioanalytical Chemistry 401 (5): 1559–1569. doi:10.1007/s00216-011-5076-2. PMID 21573842., Vernhet, A.; Dubascoux, S. P.; Cabane, B.; Fulcrand, H. L. N.; Dubreucq, E.; Poncet-Legrand, C. L. (2011). "Characterization of oxidized tannins: Comparison of depolymerization methods, asymmetric flow field-flow fractionation and small-angle X-ray scattering". Analytical and Bioanalytical Chemistry 401 (5): 1559–1569. doi:10.1007/s00216-011-5076-2. PMID 21573842.
  43. ↑ Lange, B. M.; Lapierre, C.; Sandermann Jr, H. (1995). "Elicitor-Induced Spruce Stress Lignin (Structural Similarity to Early Developmental Lignins)". Plant physiology 108 (3): 1277–1287. PMC 157483. PMID 12228544.
  44. ↑ 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
  45. ↑ Zhang, L. L.; Lin, Y. M. (2008). "HPLC, NMR and MALDI-TOF MS Analysis of Condensed Tannins from Lithocarpus glaber Leaves with Potent Free Radical Scavenging Activity". Molecules 13 (12): 2986–2997. doi:10.3390/molecules13122986. PMID 19052523.

Further reading

External links