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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.
Condensed tannins can be characterised by a number of techniques including depolymerisation, asymmetric flow field flow fractionation or small-angle X-ray scattering.
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.
Total phenols (or antioxidant effect) can be measured using the Folin-Ciocalteu reaction. Results are typically expressed as gallic acid equivalents (GAE).
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%.
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.
The information that red wine consumption is associated with favorable intake of health-promoting flavonoids that correlate positively with oxygen radical absorbance capacity (ORAC) attracted the attention of public news media.
In red wines, total oligomeric proanthocyanidin 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 proanthocyanidins (r = 0.87, P < 0.05).
In white wines, a significant correlation was found between the trimeric proanthocyanidin 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.
Proanthocyanidins are the principal vasoactive polyphenols in red wine that are linked to a reduced risk of coronary heart disease and to lower overall mortality. Proanthocyanidins 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.
Proanthocyanidins suppress production of a protein endothelin-1 that constricts blood vessels.
These studies provide data supporting the French Paradox that hypothesizes that intake of proanthocyanidins 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.
Proanthocyanidins 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, proanthocyanidins 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, proanthocyanidins 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 proanthocyanidins antioxidant capabilities are 20 times more powerful than vitamin C and 50 times more potent than vitamin E. Proanthocyanidins 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. Proanthocyanidins also have an affinity for cell membranes, providing nutritional support to reduce capillary permeability and fragility. Although flavonoids are widespread in nature, the powerful proanthocyanidin compound is most abundant and available from the bark of the maritime pine and in grape seeds, or pips. In addition, the particular proanthocyanidins 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. Additionally, this same preparation, Pycnogenol, has been found to normalize platelet adhesion (aggregation) so as to facilitate normal blood flow. 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."
Other molecules or extracts may find a way as approved drugs with therapeutic indication. For instance, Crofelemer (USAN, trade name Fulyzaq) is a drug under development for the treatment of diarrhea associated with anti-HIV drugs.
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 cinnamon, 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.
Proanthocyanidins have antioxidant properties in vitro. Foods rich in proanthocyanidins have high oxygen radical absorbance capacity, an in vitro measure with unproven relationship to antioxidant effects in vivo. 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. USDA does maintain a database of proanthocyanidin content and structure for many foods, but proanthocyanidin content in dietary supplements has not been well documented.
In one preliminary human study, cocoa procyanidins may have influenced platelet function. In one study on mice, proanthocyanidins may have had antidepressant effects and MAO inhibitory properties.
A French maritime pine bark extract of PCOs, pycnogenol, might affect microcirculation, retinal edema and visual acuity, according to one study. 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. Pycnogenol is under study for its possible influence on blood glucose (sugar) levels.
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. Many other foods and beverages may also contain PCOs, but few attain the levels found in red grape seeds and skins.
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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.
^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.
^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
^ abSánchez-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.
^ 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.
^Shi, John; Yu, Jianmel; Pohorly, Joseph E.; Kakuda, Yukio (2003). "Polyphenolics in Grape SeedsBiochemistry and Functionality". Journal of Medicinal Food6 (4): 291–9. doi:10.1089/109662003772519831. PMID14977436.
^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 Research30 (9): 775–80. doi:10.1291/hypres.30.775. PMID18037769.|displayauthors= suggested (help)
^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.
^Schoonees, A; Visser, J; Musekiwa, A; Volmink, J (2012). "Pycnogenol(®) for the treatment of chronic disorders". In Volmink, Jimmy. Cochrane Database Syst Rev.2012 (2): 008294. doi:10.1002/14651858.CD008294.pub3. PMID22336841.Unknown parameter |unused_data= ignored (help)
^Rösch, Daniel; 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.
^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.
^Steigerwalt, Robert; Belcaro, Gianni; Cesarone, Maria Rosaria; Di Renzo, Andrea; Grossi, Maria Giovanna; Ricci, Andrea; Dugall, Mark; Cacchio, Marisa et al. (2009). "Pycnogenol Improves Microcirculation, Retinal Edema, and Visual Acuity in Early Diabetic Retinopathy". Journal of Ocular Pharmacology and Therapeutics25 (6): 537–540. doi:10.1089/jop.2009.0023. PMID19916788. Lay summary – Horphag Research (December 2, 2009).|displayauthors= suggested (help)
^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.
^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.
^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.
Campagna P (2008). Farmaci vegetali – Manuale ragionato di fitoterapia. Torino: Minerva Medica. ISBN978-88-7711-603-1.
Nakamura, Yumiko; Tsuji, Sumiko; Tonogai, Yasuhide (2003). "Analysis of Proanthocyanidins in Grape Seed Extracts, Health Foods and Grape Seed Oils". Journal of Health Science49: 45–54. doi:10.1248/jhs.49.45.