Procyanidin polymeric

The procyanidins polymerized during the various reactions oxidize other components in the medium, especially ethanol into ethanal. 

By definition procyanidins and anthocyanogens, on treatment with acid, give anthocyanidins which show maximum light absorption at about 545 nm. By measurement at 455 nm estimates of the amount of catechin present can also be obtained [51]. The yield of anthocyanidin from different procyanidin fractions varies and anthocyanogen values do not correlate with the shelf life of beers. In many cases the yield of anthocyanidin released by add decreases as the procyanidins polymerize while the level of total polyphenols (EBQ remains roughly constant. Accordingly the... 

Epicatechin and catechin (Fig. 74.4) represent the basis on which to build more complex molecules such as procyanidin polymeric forms. Proanthocyanidins are polymer chains of flavonoids such as flavan-3-ols. Mainly, two primary forms of procyanidins occur in plants A-type and B-type, which differ by the linkage between individual compounds. A-type procyanidins form 4—8 and 2-7 cross-links and has... 

The discovery of flavan-3-ols and their procyanidin polymeric forms in cocoa can be traced back to the beginning of the last century and are now identified as catechins [26-28]. In 1939, leucoanthocyanin phenolic compounds were identified [29] and, in 1955, fractionation and characterization of these compounds were reported [30]. Procyanidins in cocoa have more recently been fractionated into monomers through decamers with even higher forms existing [31]. 

SAR studies were carried out by de Bruyne et al. [92] on a series of dimeric procyanidins, considered as model compounds for antiviral therapies. On the whole, proanthocyanidins containing EC dimers exhibited more pronounced activity against herpes simplex virus (HSV) and human immunodeficiency virus (HIV), while the presence of ortho-trihydroxyl groups in the B-ring appeared to be essential in all proanthocyanidins exhibiting anti-HSV effects. Galloylation and polymerization reinforced the antiviral activities markedly. 

Lea AGH. 1978. The phenolics of ciders oligomeric and polymeric procyanidins. J Sci Food Agric... 

Proanthocyanidins (PAs), also known as condensed tannins, are oligomeric and polymeric flavan-3-ols. Procyanidins are the main PAs in foods however, prodelphinidins and propelargonidins have also been identified (Gu and others 2004). The main food sources of total PAs are cinnamon, 8084 mg/100 g FW, and sorghum, 3937 mg/100 g FW. Other important sources of PAs are beans, red wine, nuts, and chocolate, their content ranging between 180 and 300 mg/100 g FW. In fruits, berries and plums are the major sources, with 213.6 and 199.9 mg/100 g FW, respectively. Apples and grapes are intermediate sources of PAs (60 to 90 mg/100 g FW), and the content of PAs in other fruits is less than 40 mg/100 g FW. In the majority of vegetables PAs are not detected, but they can be found in small concentrations in Indian squash (14.8 mg/ 100 g FW) (Gu and others, 2004 US Department of Agriculture, 2004). 

Flavanols and procyanidins Flavanols, or flavan-3-ols, are synthesized via two routes, with (+) catechins formed from flavan-3,4-diols via leucoanthocyanidin reductase (LAR), and (—) epicatechins from anthocyanidins via anthocyanidin reductase (ANR) (see Fig. 5.4). These flavan-3-ol molecules are then polymerized to condensed tannins (proanthocyanidins or procyanidins), widely varying in the number and nature of their component monomers and linkages (Aron and Kennedy 2008 Deluc and others 2008). It is still not known whether these polymerization reactions happen spontaneously, are enzyme catalyzed, or result from a mixture of both. 

Polymeric procyanidin extraction from black beans (Phaseolus vulgaris L. cv. Black Turtle Soup) and purification was a... 

Prieur C, Rigaud J, Cheynier V et al (1994) Oligomeric and polymeric procyanidins from grape seeds. Phytochemistry 36 781-784... 

Guyot S, Doco T, Souquet JM et al (1997) Characterization of highly polymerized procyanidins in cider apple skin and pulp. Phytochemistry 44 351-357... 

Takahata Y, Ohnishi-Kameyama M, Furuta S et al (2001) Highly polymerized procyanidins in brown soybean seed coat with a high radical-scavenging activity. J Agric Food Chem 49 5843-5847... 

Kusuda M, Inada K, Ogawa TO, Yoshida T, Shiota T, Shiota S, Tsuchiya T, Hatano T. (2006) Polyphenolic constituents structures of Zanthoxylum piper-itum fruit and the antibacterial effects of its polymeric procyanidin on methicillin-resistant Staphylococcus aureus. Biosci Biotechnol Biochem 70 1423-1431. 

The two principal classes of proanthocyanidins found (10) in plant tissues are the procyanidins (1, R e H) and the prodeTphin-idins (1, R s OH). Proanthocyanidins of mixed anthocyanidin character (1, R = H or OH) have been noted. In any tissue where proanthocyan din synthesis occurs there is invariably found a range of molecular species - from the monomeric flavan-3-ols (catechins, gallocatechins) to the polymeric forms (1) and biosynthetic work (11) suggests a very close relationship between the metabolism of the parent f1avan-3-o1 and the synthesis of proanthocyanidins, Figure 4. 

Condensed tannins (= proanthocyanidins) unlike hydrolysable tannins, condensed tannins are polymeric flavans that are not readily hydrolysable. They often consist of molecules of catechin and epicatechin joined by carbon-carbon bonds. Hence catechin and epicatechin are referred to as monomers oligomers containing 2-4 (epi)catechin units are referred to as oligomeric procyanidins (OPC). 

The phenolic composition of apple consists of cinnamic acids, flavonols, dihydrochalcones, and flavan-3-ols (50,56). In the apple fruit processing industry, hydroxycinnamic acid derivatives and flavan-3-ols are important due to their contribution to the astringency, haze, and browning in apple juice and cider. Chlorogenic acid represents the major hydroxycinnamic acid derivative. The flavan-3-ols (catechins) are present in the monomeric form as well as in oligomeric and polymeric forms (procyanidins) in apple and apple products (56). 

Condensed tannins are also referred to as proanthocyanidins. They are oligomeric or polymeric flavonoids consisting of flavan-3-ol (catechin) units. Hydrolysis under harsh conditions, such as heating in acid, yields anthocyanidins. An example of a condensed tannin is procyanidin B2 (epicatechin-(4 3—>8 )-epicatechin 1.90). In this case the interflavanyl linkage is between C4 of the lower unit, and C8 of the upper unit. The linkage can also be between C4 of one unit and C6 of the second unit. 

Polymeric tannins are complex molecules comprising flavan-3-ols or catechins, and called "procyanidins" 48, 49a-d ... 

---