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Epicatechin (EC), one of the building blocks of proanthocyanidins
Proanthocyanidins, refer to a larger class of polyphenols, called flavanols, in which occur PCOs (proanthocyanidin oligomers) or OPCs (oligomeric proanthocyanidins), the simplest flavanols. More complex polyphenols, having the same polymeric building block, form the group of tannins. Flavanols are distinguished at the core molecule by the hydroxyl group as opposed to the ketone near same position on the pyran ring in the generally yellow class of flavonoids. Colorless PCOs or OPCs are a strictly defined group of 3 flavanols naturally occurring as a mix of monomers, di-mers, and tri-mers of the catechin building block, which is a 4x-hydroxylation of the flavan-3-ol core.
PCOs or OPCs were discovered in 1947 by Prof. Jacques Masquelier, who developed and patented techniques for the extraction of oligomeric proanthocyanidins from pine bark and grape seeds.
DMACA is a dye that is particularly useful for localization of proanthocyanidin compounds in plant histology. The use of the reagent results in blue staining. It can also be used to titrate proanthocyanidins.
Proanthocyanidins 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%.
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 seeds and skin, hence in red wine and grape seed extract, in cocoa, nuts, apples and all Prunus fruits (most concentrated in the skin) and in the bark of Cinnamomum (cinnamon) and Pinus pinaster (formerly known as Pinus maritima). It can also be found in berries like blueberry and cranberry (notably procyanidin A2) and fruits from wild shrubs such as chokeberry, hawthorn, rosehip and sea buckthorn.
In red wines, total oligomeric proanthocyanidin content, including flavan-3-ols (catechins), was substantially higher (177 mg/L) than that in white wines (9 mg/L). A relatively high correlation in red wines was found between ORAC values and proanthocyanidins. These studies support conjecture about the French Paradox which hypothesizes that intake of proanthocyanidins and other flavonoids from regular consumption of red wines lowers risk of cardiovascular diseases or diabetes in French citizens on high-fat diets.
Other basic research
Proanthocyanidins have antioxidant activity in vitro and may play a role in the stabilization of collagen and maintenance of elastin — two proteins in connective tissue that support organs, joints, blood vessels, muscle and dentin. Common dietary antioxidants are vitamin C and vitamin E; however, in vitro studies show that proanthocyanidins may have stronger antioxidant activity than vitamin C or vitamin E under laboratory conditions.
However, a 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."
In one preliminary human study, cocoa procyanidins also influenced platelet function. In one study on mice, proanthocyanidins had antidepressant effects and MAO inhibitory properties.
Proanthocyanidins are present in fresh grapes, grape juice, and red wine. Although red wine may contain more proanthocyanidins than red grape juice, red grape juice contains more proanthocyanidins per average serving size. An 8-ounce serving of grape juice averages 124 milligrams proanthocyanidins, whereas a 5-ounce serving of red wine averages 91 milligrams. Many other foods and beverages may also contain proanthocyanidins, but few attain the levels found in red grape seeds and skins.
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 proanthocyanidins characterisation in wine or in the grape seed and skin tissues.
^Schwitters, Bert (1995). OPC in Practice. Publishing rights search incomplete. p. 15. ISBN88-86035-13-6.
^ abMaría Luisa Mateos-Martín, Elisabet Fuguet, Carmen Quero, Jara Pérez-Jiménez, Josep Lluís Torres.; Fuguet; Quero; Pérez-Jiménez; Torres (2012). "New identification of proanthocyanidins in cinnamon (Cinnamomum zeylanicum L.) using MALDI-TOF/TOF mass spectrometry". Analytical and Bioanalytical Chemistry402 (3): 1327–1336. doi:10.1007/s00216-011-5557-3. PMID22101466.
^Souquet, J; Cheynier, Véronique; Brossaud, Franck; Moutounet, Michel (1996). "Polymeric proanthocyanidins from grape skins". Phytochemistry43 (2): 509. doi:10.1016/0031-9422(96)00301-9.
^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 therapeutics40 (4): 158–68. PMID11996210.
^Hatano, T; Miyatake, H; Natsume, M; Osakabe, N; Takizawa, T; Ito, H; Yoshida, T (2002). "Proanthocyanidin glycosides and related polyphenols from cacao liquor and their antioxidant effects". Phytochemistry59 (7): 749–58. doi:10.1016/S0031-9422(02)00051-1. PMID11909632.
^Merghem, R.; Jay, M.; Brun, N.; Voirin, B. (2004). "Qualitative analysis and HPLC isolation and identification of procyanidins fromvicia faba". Phytochemical Analysis15 (2): 95–99. doi:10.1002/pca.731. PMID15116939.
^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 Nutrition68 (3): 793. doi:10.1079/BJN19920134.
^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 Agriculture32 (8): 797. doi:10.1002/jsfa.2740320808.
^Cabrera, A.; Martin, A. (2009). "Genetics of tannin content and its relationship with flower and testa colours in Vicia faba". The Journal of Agricultural Science113: 93. doi:10.1017/S0021859600084665.
^Kristensen, H.; Aastrup, S. (1986). "A non-destructive screening method for proanthocyanidin-free barley mutants". Carlsberg Research Communications51 (7): 509. doi:10.1007/BF02906893.
^Stringano, E; Gea, A; Salminen, J. P.; Mueller-Harvey, I (2011). "Simple solution for a complex problem: Proanthocyanidins, galloyl glucoses and ellagitannins fit on a single calibration curve in high performance-gel permeation chromatography". Journal of Chromatography A1218 (43): 7804–12. doi:10.1016/j.chroma.2011.08.082. PMID21930278. edit
^Engström, M. T.; Pälijärvi, M; Fryganas, C; Grabber, J. H.; Mueller-Harvey, I; Salminen, J. P. (2014). "Rapid Qualitative and Quantitative Analyses of Proanthocyanidin Oligomers and Polymers by UPLC-MS/MS". Journal of Agricultural and Food Chemistry62 (15): 3390–9. doi:10.1021/jf500745y. PMID24665824. edit
^Torres, J. L.; Lozano, C. (2001). "Chromatographic characterization of proanthocyanidins after thiolysis with cysteamine". Chromatographia54 (7–8): 523. doi:10.1007/BF02491211.
^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 Chemistry52 (8): 2292–6. doi:10.1021/jf035311i. PMID15080635.
^Tandem mass spectrometry for sequencing proanthocyanidins. Li Hui-Jing and Deinzer Max L., Analytical chemistry, 2007, volume 79, no 4, pages 1739-1748, INIST:18534021
^Taheri, Daniel R.; Connolly, Bryan A.; Brand, Mark H.; Bolling, Bradley W. (2013). "Underutilized Chokeberry (Aronia melanocarpa, Aronia arbutifolia, Aronia prunifolia) Accessions Are Rich Sources of Anthocyanins, Flavonoids, Hydroxycinnamic Acids, and Proanthocyanidins". Journal of Agricultural and Food Chemistry61 (36): 8581–8. doi:10.1021/jf402449q. PMID23941506.
^Rösch, Daniel R.; Mügge, Clemens; Fogliano, Vincenzo; Kroh, Lothar W. (2004). "Antioxidant Oligomeric Proanthocyanidins from Sea Buckthorn (Hippophaë rhamnoides) Pomace". Journal of Agricultural and Food Chemistry52 (22): 6712–8. doi:10.1021/jf040241g. PMID15506806.
^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 - Plant36 (6): 492. doi:10.1007/s11627-000-0088-1.
^Amil-Ruiz, F.; Blanco-Portales, R.; Munoz-Blanco, J.; Caballero, J. L. (2011). "The Strawberry Plant Defense Mechanism: A Molecular Review". Plant and Cell Physiology52 (11): 1873–903. doi:10.1093/pcp/pcr136. PMID21984602.edit
^ abcCorder, 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". Nature444 (7119): 566. doi:10.1038/444566a. PMID17136085.
^Absalon, C; Fabre, S; Tarascou, I; Fouquet, E; Pianet, I (2011). "New strategies to study the chemical nature of wine oligomeric procyanidins". Analytical and Bioanalytical Chemistry401 (5): 1485–95. doi:10.1007/s00216-011-4988-1. PMID21573848. edit
^Gonzalo-Diago, A; Dizy, M; Fernández-Zurbano, P (2013). "Taste and mouthfeel properties of red wines proanthocyanidins and their relation to the chemical composition". Journal of Agricultural and Food Chemistry61 (37): 8861–70. doi:10.1021/jf401041q. PMID23889258. edit
^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 Chemistry51 (17): 4889–96. doi:10.1021/jf030081t. PMID12903941.
^ abShi, John; Yu, Jianmel; Pohorly, Joseph E.; Kakuda, Yukio (2003). "Polyphenolics in Grape Seeds: Biochemistry and Functionality". Journal of Medicinal Food6 (4): 291–9. doi:10.1089/109662003772519831. PMID14977436.
^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 research95 (4): 155–61. doi:10.1016/S0049-3848(99)00030-4. PMID10498385.
^Liu, Ximing; Zhou, Ha-Jun; Rohdewald, Peter (2004). "French Maritime Pine Bark Extract Pycnogenol Dose-Dependently Lowers Glucose in Type 2 Diabetic Patients". Diabetes Care27 (3): 839. doi:10.2337/diacare.27.3.839.
^Schäfer, Angelika; Högger, Petra (2007). "Oligomeric procyanidins of French maritime pine bark extract (Pycnogenol) effectively inhibit α-glucosidase". Diabetes Research and Clinical Practice77 (1): 41–6. doi:10.1016/j.diabres.2006.10.011. PMID17098323.
^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. PMID19857512.
^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 Chemistry45 (4): 1195. doi:10.1021/jf9607573.
^ abLiu, H; Zou, T; Gao, J. M.; Gu, L (2013). "Depolymerization of cranberry procyanidins using (+)-catechin, (-)-epicatechin, and (-)-epigallocatechin gallate as chain breakers". Food Chemistry141 (1): 488–94. doi:10.1016/j.foodchem.2013.03.003. PMID23768384. edit
^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 Chemistry49 (4): 1740–1746. doi:10.1021/jf001030o. PMID11308320.
^Sears, K. D.; Casebier, R. L. (1968). "Cleavage of proanthocyanidins with thioglycollic acid". Chemical Communications (London) (22): 1437. doi:10.1039/C19680001437.
^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 Chemistry401 (5): 1559–1569. doi:10.1007/s00216-011-5076-2. PMID21573842., 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 Chemistry401 (5): 1559–1569. doi:10.1007/s00216-011-5076-2. PMID21573842.
^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". Molecules13 (12): 2986–2997. doi:10.3390/molecules13122986. PMID19052523.