Procyanidin B5 is a B type proanthocyanidin .
31-567: Procyanidin B5 is an epicatechin -(4β → 6)-epicatechin dimer. It can be found in grape seeds, in Hibiscus cannabinus (kenaf) root and bark, and in black chokeberries ( Aronia melanocarpa ). It is found in cocoa beans and chocolate. This article about an aromatic compound is a stub . You can help Misplaced Pages by expanding it . Epicatechin Catechin / ˈ k æ t ɪ k ɪ n /
62-427: A hydroxyl group on carbon 3. The A ring is similar to a resorcinol moiety while the B ring is similar to a catechol moiety. There are two chiral centers on the molecule on carbons 2 and 3. Therefore, it has four diastereoisomers . Two of the isomers are in trans configuration and are called catechin and the other two are in cis configuration and are called epicatechin . The most common catechin isomer
93-564: A (2 S )-phenyl group resisted the biooxidation. Leucoanthocyanidin reductase (LAR) uses (2 R ,3 S )-catechin, NADP and H 2 O to produce 2,3- trans -3,4- cis - leucocyanidin , NADPH, and H . Its gene expression has been studied in developing grape berries and grapevine leaves. Only limited evidence from dietary studies indicates that catechins may affect endothelium -dependent vasodilation which could contribute to normal blood flow regulation in humans. Green tea catechins may improve blood pressure, especially when systolic blood pressure
124-434: A pseudoaxial position (A conformer). Studies confirmed that (+)-catechin adopts a mixture of A- and E-conformers in aqueous solution and their conformational equilibrium has been evaluated to be 33:67. As flavonoids, catechins can act as antioxidants when in high concentration in vitro , but compared with other flavonoids, their antioxidant potential is low. The ability to quench singlet oxygen seems to be in relation with
155-489: A spring or mine drainage to evaporate —and gum arabic from acacia trees; this combination of ingredients produced the ink. Gallic acid was one of the substances used by Angelo Mai (1782–1854), among other early investigators of palimpsests , to clear the top layer of text off and reveal hidden manuscripts underneath. Mai was the first to employ it, but did so "with a heavy hand", often rendering manuscripts too damaged for subsequent study by other researchers. Gallic acid
186-404: A two-step oxidation can be achieved by Burkholderia sp. (+)-Catechin and (−)-epicatechin are transformed by the endophytic filamentous fungus Diaporthe sp. into the 3,4-cis-dihydroxyflavan derivatives, (+)-(2 R ,3 S ,4 S )-3,4,5,7,3′,4′-hexahydroxyflavan (leucocyanidin) and (−)-(2 R ,3 R ,4 R )-3,4,5,7,3′,4′-hexahydroxyflavan , respectively, whereas (−)-catechin and (+)-epicatechin with
217-437: Is (+)-catechin. The other stereoisomer is (−)-catechin or ent -catechin. The most common epicatechin isomer is (−)-epicatechin (also known under the names L -epicatechin, epicatechol, (−)-epicatechol, L -acacatechin, L -epicatechol, epicatechin, 2,3- cis -epicatechin or (2 R ,3 R )-(−)-epicatechin). The different epimers can be separated using chiral column chromatography . Making reference to no particular isomer,
248-439: 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 tannic juice or boiled extract of Mimosa catechu ( Acacia catechu L.f). Catechin possesses two benzene rings (called the A and B rings) and a dihydropyran heterocycle (the C ring) with
279-469: Is a trihydroxybenzoic acid with the formula C 6 H 2 ( OH ) 3 CO 2 H. It is classified as a phenolic acid . It is found in gallnuts , sumac , witch hazel , tea leaves, oak bark , and other plants . It is a white solid, although samples are typically brown owing to partial oxidation. Salts and esters of gallic acid are termed "gallates". Its name is derived from oak galls , which were historically used to prepare tannic acid . Despite
310-1359: Is a reversible reaction. The hydroxyl groups of the resorcinol moiety oxidised afterwards were shown to undergo an irreversible oxidation reaction. The laccase / ABTS system oxidizes (+)-catechin to oligomeric products of which proanthocyanidin A2 is a dimer. (500 MHz, CD3OD): Reference d : doublet, dd : doublet of doublets, m : multiplet, s : singlet 2.49 (1H, dd, J = 16.0, 8.6 Hz, H-4a), 2.82 (1H, dd, J = 16.0, 1.6 Hz, H-4b), 3.97 (1H, m, H-3), 4.56 (1H, d, J = 7.8 Hz, H-2), 5.86 (1H, d, J = 2.1 Hz, H-6), 5.92 (1H, d, J = 2.1 Hz, H-8), 6.70 (1H, dd, J = 8.1, 1.8 Hz, H-6'), 6.75 (1H, d, J = 8.1 Hz, H-5'), 6.83 (1H, d, J = 1.8 Hz, H-2') 273 water loss 139 retro Diels–Alder 123 165 147 (+)-Catechin and (−)-epicatechin as well as their gallic acid conjugates are ubiquitous constituents of vascular plants , and frequent components of traditional herbal remedies , such as Uncaria rhynchophylla . The two isomers are mostly found as cacao and tea constituents, as well as in Vitis vinifera grapes. The main dietary sources of catechins in Europe and
341-414: Is above 130 mmHg. Due to extensive metabolism during digestion, the fate and activity of catechin metabolites responsible for this effect on blood vessels, as well as the actual mode of action, are unknown. Catechin and its metabolites can bind tightly to red blood cells and thereby induce the development of autoantibodies , resulting in haemolytic anaemia and renal failure . This resulted in
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#1732780463850372-515: Is biosynthesized from L -phenylalanine through the Shikimate pathway. L -Phenylalanine is first deaminated by phenylalanine ammonia lyase (PAL) forming cinnamic acid which is then oxidized to 4-hydroxycinnamic acid by cinnamate 4-hydroxylase. Chalcone synthase then catalyzes the condensation of 4-hydroxycinnamoyl CoA and three molecules of malonyl-CoA to form chalcone . Chalcone is then isomerized to naringenin by chalcone isomerase which
403-720: Is formed from 3-dehydroshikimate by the action of the enzyme shikimate dehydrogenase to produce 3,5-didehydroshikimate. This latter compound aromatizes . Alkaline solutions of gallic acid are readily oxidized by air. The oxidation is catalyzed by the enzyme gallate dioxygenase , an enzyme found in Pseudomonas putida . Oxidative coupling of gallic acid with arsenic acid, permanganate, persulfate, or iodine yields ellagic acid , as does reaction of methyl gallate with iron(III) chloride . Gallic acid forms intermolecular esters ( depsides ) such as digallic and cyclic ether-esters ( depsidones ). Hydrogenation of gallic acid gives
434-656: Is metabolized to protocatechuic acid (PCA) and phloroglucinol carboxylic acid (PGCA). It is also degraded by Bradyrhizobium japonicum . Phloroglucinol carboxylic acid is further decarboxylated to phloroglucinol , which is dehydroxylated to resorcinol . Resorcinol is hydroxylated to hydroxyquinol . Protocatechuic acid and hydroxyquinol undergo intradiol cleavage through protocatechuate 3,4-dioxygenase and hydroxyquinol 1,2-dioxygenase to form β-carboxy- cis , cis -muconic acid and maleyl acetate . Among fungi, degradation of catechin can be achieved by Chaetomium cupreum . Catechins are metabolised upon uptake from
465-406: Is oxidized to eriodictyol by flavonoid 3′-hydroxylase and further oxidized to taxifolin by flavanone 3-hydroxylase. Taxifolin is then reduced by dihydroflavanol 4-reductase and leucoanthocyanidin reductase to yield catechin. The biosynthesis of catechin is shown below Leucocyanidin reductase (LCR) uses 2,3- trans -3,4- cis - leucocyanidin to produce (+)-catechin and is the first enzyme in
496-402: The calotype to make the silver more sensitive to light; it was also used in developing photographs. Gallic acid is found in a number of land plants , such as the parasitic plant Cynomorium coccineum , the aquatic plant Myriophyllum spicatum , and the blue-green alga Microcystis aeruginosa . Gallic acid is also found in various oak species, Caesalpinia mimosoides , and in
527-406: The colonic microbiome to gamma-valerolactones and hippuric acids which undergo further biotransformation , glucuronidation , sulfation and methylation in the liver . The stereochemical configuration of catechins has a strong impact on their uptake and metabolism as uptake is highest for (−)-epicatechin and lowest for (−)-catechin. Biotransformation of (+)-catechin into taxifolin by
558-414: The gastrointestinal tract , in particular the jejunum , and in the liver , resulting in so-called structurally related epicatechin metabolites (SREM). The main metabolic pathways for SREMs are glucuronidation , sulfation and methylation of the catechol group by catechol-O-methyl transferase , with only small amounts detected in plasma. The majority of dietary catechins are however metabolised by
589-531: The proanthocyanidin (PA) specific pathway. Its activity has been measured in leaves, flowers, and seeds of the legumes Medicago sativa , Lotus japonicus , Lotus uliginosus , Hedysarum sulfurescens , and Robinia pseudoacacia . The enzyme is also present in Vitis vinifera (grape). [REDACTED] Catechin oxygenase, a key enzyme in the degradation of catechin, is present in fungi and bacteria. Among bacteria, degradation of (+)-catechin can be achieved by Acinetobacter calcoaceticus . Catechin
620-600: The European ecosystem have defenses against catechin, but few plants are protected against it in the North American ecosystem where Centaurea maculosa is an invasive, uncontrolled weed. Catechin acts as an infection-inhibiting factor in strawberry leaves. Epicatechin and catechin may prevent coffee berry disease by inhibiting appressorial melanization of Colletotrichum kahawae . Gallic acid Gallic acid (also known as 3,4,5-trihydroxybenzoic acid )
651-636: The United States are tea and pome fruits. Catechins and epicatechins are found in cocoa , which, according to one database, has the highest content (108 mg/100 g) of catechins among foods analyzed, followed by prune juice (25 mg/100 ml) and broad bean pod (16 mg/100 g). Açaí oil , obtained from the fruit of the açaí palm ( Euterpe oleracea ), contains (+)-catechins (67 mg/kg). Catechins are diverse among foods, from peaches to green tea and vinegar . Catechins are found in barley grain, where they are
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#1732780463850682-475: The chemical structure of catechin, with the presence of the catechol moiety on ring B and the presence of a hydroxyl group activating the double bond on ring C. Electrochemical experiments show that (+)-catechin oxidation mechanism proceeds in sequential steps, related with the catechol and resorcinol groups and the oxidation is pH-dependent. The oxidation of the catechol 3′,4′-dihydroxyl electron-donating groups occurs first, at very low positive potentials, and
713-409: The cyclohexane derivative hexahydrogallic acid. Heating gallic acid gives pyrogallol (1,2,3-trihydroxybenzene). This conversion is catalyzed by gallate decarboxylase . Many esters of gallic acid are known, both synthetic and natural. Gallate 1-beta-glucosyltransferase catalyzes the glycosylation (attachment of glucose) of gallic acid. Gallic acid is an important component of iron gall ink ,
744-445: The ground by some plants may hinder the growth of their neighbors, a form of allelopathy . Centaurea maculosa , the spotted knapweed often studied for this behavior, releases catechin isomers into the ground through its roots, potentially having effects as an antibiotic or herbicide . One hypothesis is that it causes a reactive oxygen species wave through the target plant's root to kill root cells by apoptosis . Most plants in
775-414: The main phenolic compound responsible for dough discoloration. The taste associated with monomeric (+)-catechin or (−)-epicatechin is described as slightly astringent , but not bitter. [REDACTED] The biosynthesis of catechin begins with ma 4-hydroxycinnamoyl CoA starter unit which undergoes chain extension by the addition of three malonyl-CoAs through a PKSIII pathway. 4-Hydroxycinnamoyl CoA
806-540: The molecule can just be called catechin. Mixtures of the different enantiomers can be called (±)-catechin or DL -catechin and (±)-epicatechin or DL -epicatechin. Catechin and epicatechin are the building blocks of the proanthocyanidins , a type of condensed tannin. Moreover, the flexibility of the C-ring allows for two conformation isomers , putting the B-ring either in a pseudoequatorial position (E conformer) or in
837-404: The name, gallic acid does not contain gallium . Gallic acid is easily freed from gallotannins by acidic or alkaline hydrolysis . When heated with concentrated sulfuric acid , gallic acid converts to rufigallol . Hydrolyzable tannins break down on hydrolysis to give gallic acid and glucose or ellagic acid and glucose, known as gallotannins and ellagitannins , respectively. Gallic acid
868-706: The standard European writing and drawing ink from the 12th to 19th centuries, with a history extending to the Roman empire and the Dead Sea Scrolls . Pliny the Elder (23–79 AD) describes the use of gallic acid as a means of detecting an adulteration of verdigris and writes that it was used to produce dyes. Galls (also known as oak apples) from oak trees were crushed and mixed with water, producing tannic acid . It could then be mixed with green vitriol ( ferrous sulfate )—obtained by allowing sulfate-saturated water from
899-430: The stem bark of Boswellia dalzielii , among others. Many foodstuffs contain various amounts of gallic acid, especially fruits (including strawberries, grapes, bananas), as well as teas , cloves, and vinegars . Carob fruit is a rich source of gallic acid (24–165 mg per 100 g). Also known as galloylated esters: Gallate esters are antioxidants useful in food preservation, with propyl gallate being
930-633: The withdrawal of the catechin-containing drug Catergen, used to treat viral hepatitis , from market in 1985. Catechins from green tea can be hepatotoxic and the European Food Safety Authority has recommended not to exceed 800 mg per day. One limited meta-analysis showed that increasing consumption of green tea and its catechins to seven cups per day provided a small reduction in prostate cancer . Nanoparticle methods are under preliminary research as potential delivery systems of catechins. Catechins released into
961-508: Was first studied by the Swedish chemist Carl Wilhelm Scheele in 1786. In 1818, French chemist and pharmacist Henri Braconnot (1780–1855) devised a simpler method of purifying gallic acid from galls; gallic acid was also studied by the French chemist Théophile-Jules Pelouze (1807–1867), among others. When mixed with acetic acid , gallic acid had uses in early types of photography, like