Procyanidine

Fig. 3. The regular structure of a procyanidin-type condensed tannin showing characteristic 4,8 interflavonoid bonds linking the flavonoid units.

NARDINI M, SCACCINI c, PACKER L and VIRGILI F (2000) In vivo inhibition of the activity of phosphorylase kinase, protein kinase C and protein kinase A by caffeic acid and a procyanidin rich pine bark (Pinus maritima) extract Biochimica Biophysica Acta 1474, 219-25. 

RiMBACH G, VIRGILI F, PARK Y c and PACKER L (1999) Effect of procyanidins fromPinus maritima on glutathione levels in endothelial cells challenged by 3-morpholinosyndonimine or activated macrophages Redox Report 4, 171-7. 

Proanthocyanidins are an important group of di- to oligomeric flavonoids in plants. Four proanthocyanidins (procyanidin B3, prodelphinidin B4, ECG-(4 8)-ECG and GC-(4 8)-EGCG) were determined quantitatively in tea. The amounts in fresh tea leaves were between 1 and 2 g/kg per compound (Nakabayashi, 1991). The occurrence of proanthocyanidins may serve as a criterion for the differentiation between fermented and non-fermented teas (Kiehne et al, 1997). 

Kolodziej, H., Occurrence of procyanidins in Nelia meyeri, Phytochemistry, 23,1745, 1984. 

The effects of catechin, epicatechin, procyanidin B2, caffeic acid, / -coumaric acid, myricetrin, and quercetrin on the color intensity and stability of malvidin 3-glucoside at a molar ratio of 1 1 under conditions similar to red wine were evaluated. " Flavan 3-ols appeared to have the lowest protective effects and flavonols the highest strong color changes were visually perceptible. " In the complexation of malvin chloride and natural polyphenols, flavonol glycosides by far exerted the best protector effect. ... 

Berke, B. and de Freitas, V.A.P., Influence of procyanidin structures on their ability to complex with oenin. Food Chem., 90, 3, 453, 2005. 

Pati, S. et al.. Simultaneous separation and identification of oligomeric procyanidins and anthocyanin-derived pigments in raw red wine by HPLC-UV-ESI-MS, J. Mass Spectrom., 41, 861, 2006. 

Thousands of polyphenols from fruits (grapes, apples, etc.), vegetables (horse beans), and teas have been identified, many having good coloring properties, especially anthocyanins and some flavonoids. Well-documented reviews discuss the coloring capacities of some polyphenols including procyanidins. - Detailed presentations of anthocyanin and flavonoid properties and analysis are included in Sections 2.3, 4.3, and 6.3. The soluble proanthocyanidins of the colored horse bean Viciafaba L. seed coats were isolated and separated by solvent partition. 

The B-type procyanidins include a mixture of oligomers and polymers composed of flavan-3-ol units linked mainly through C4 C8 and/or C4 C6 bonds, and represent the dominant class of natural proanthocyanidins. Among the dimers, procyanidins Bl, B2, B3 and B4 (Fig. 2a) are the most frequently occurring in plant tissues. Procyanidin B5 (EC-(4j6 6)-EC), B6 (catechin-(4o 6)-catechin), B7 (EC-(4/3 6)-catechin) and B8 (catechin-(4q 6)-EC) are also widespread (Eig. 2b) [17-19]. 

Analogues of procyanidin Bl and B2 exhibiting EC chain extension units (2R, 3R-2,3-czs configuration) are very commonly represented in the plant kingdom, whereas many plants also produce analogues of procyanidin B3 to B8 [18,19]. 

The A-type proanthocyanidins are characterized by a second ether linkage between an A-ring hydroxyl group of the lower unit and C-2 of the upper unit. Since they are less frequently isolated from plants than the B-types, they have been considered unusual structures [18,19]. The first identified A-type proanthocyanidin was procyanidin A2 isolated from the shells of fruit of Aes-culus hippocastanum. Since then, many more A-type proanthocyanidins have been found in plants, including dimers, trimers, tetramers, pentamers and ethers [18,21]. 

Furthermore, C-type procyanidins include trimers composed of fiavan-3-ol units linked mainly through C4 C8 (Fig. 4). 

In a few cases, the synthesis was directed towards well-defined oligomers (dimers, trimers, etc.). The synthesis of bis(5,7,3, 4 -tetra-0-benzyl)-EC 4/1,8-dimer from 5,7,3, 4 -tetra-0-benzyl-EC and 5,7,3, 4 -tetra-0-benzyl-4-(2-hydroxyethoxy)-EC was described by Kozikowski et al. [41]. This compound exhibited the ability to inhibit the growth of several breast cancer cell fines through the induction of cell cycle arrest in the Gq/Gi phase. Analogously, procyanidin-B3, a condensed catechin dimer, has been obtained through condensation of benzylated catechin with various 4-0-alkylated flavan-3,4-diol derivatives in the presence of a Lewis acid. This reaction led to protected procyanidin-B3 and its diastereomer. In particular, octa-O-benzylated procyanidin-B3 has been produced with high levels of stereoselectivity and in excellent isolation yields [42]. 

Although the above profusion of in vivo studies evidence their health potentialities, the problem of the bioavailabihty of proanthocyanidins supplied by dietary supplementation has still not been completely resolved since unequivocal evidence for absorption is missing so far [11]. However, studies carried out using radio-labelled procyanidins revealed that dimers and trimers may be absorbed by intestinal cells, whereas a recent study demonstrated that procyanidin oligomers are readily adsorbed in rats [55], while it has been shown that colon microflora may be able to degrade proanthocyanidins to low-molecular-weight aromatic compounds [56]. 

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. 

Yanagida, A., Kanda, T., Shoji, T., Ohnishi-Kameyama, M., and Nagata, T., Fractionation of apple procyanidins by size-exclusion chromatography, /. Chromatogr. A, 855, 181, 1999. 

Anthocyanins are Che most easily assayed and commonly studied derivatives of aromatic amino acids (Figure 1). Glyphosate drastically reduces accumulation of anthocyanin flavonoids in treated tissues (6, 19) (Figure 3). Levels of rutin and procyanidin, both flavonoids, are reduced in glyphosate-treated buckwheat hypocotyls (6). Glyphosate would presumably similarly affect levels of flavonoids and flavonoid derivatives that are known to be allelochemicals. 

Some herbal products are prepared from a mixture of different plant species and plant parts. Hawthorn is standardized to contain 5% oligomeric procyanidins made from the leaves, blossoms, and fruit of Crataegus laevigata and Crataegus monogyna [6]. Studies have shown that the therapeutic efficacy of hawthorn is not solely the result of one type of component, one plant part, or a single species [6]. 

Some flavonoids, such as procyanidins, have antidiabetic properties because they improve altered glucose and oxidative metabolisms of diabetic states (Pinent and others 2004). Extract of grape seed procyanidins (PE) administered orally to streptozotocin-induced diabetic rats resulted in an antihyperglycemic effect, which was significantly increased if PE administration was accompanied by a low insulin dose (Pinent and others 2004). The antihyperglycemic effect of PE may be partially due to the insuli-nomimetic activity of procyanidins on insulin-sensitive cell lines. 

---