Dimeric procyanidins

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]. 

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. 

Monomers, dimers (procyanidin Bl, B2), and oligomers Apples, cherries, berries, grapes, peaches, pears... 

The method of Kato and Nakai (27) for determining protein surface hydrophobicity was adapted for evaluating procyanidin binding to BSA and Gl. The procedure is based on the fact that the fluorescence quantum yield of cis-parinaric acid increases 40-fold when cis-parinaric acid enters a hydrophobic environment from a hydrophilic environment. The digestion of BSA by trypsin in the presence of procyanidin dimer, procyanidin trimer and black bean procyanidin polymer was evaluated by discontinuous sodium dodecyl sulfate (SDS) slab gel electrophoresis and a picryl sulfonic acid (TNBS) assay (28). 

Trimeric procyanidin binds more tightly to BSA than dimeric procyanidin (Table II). Partition coefficients of dimeric and trimeric catechin between n-octanol and water indicate procyanidin trimer is more hydrophobic than procyanidin dimer. Increased binding constants of trimer relative to dimer agree with reported partition coefficients. Surface hydrophobicity assays with cis-parinaric acid confirm the thermodynamic analysis that binding of procyanidin to BSA is hydrophobic. 

Lokvam, J., Coley, P.D., and Kursar, T.A., Cinnamoyl glucosides of catechin and dimeric procyanidins from yormg leaves of Inga umbellifera (Fabaceae), Phytochemistry, 65, 351, 2004. 

Saito, A. et al.. Synthetic studies of proanthocyanidins. Highly stereoselective synthesis of the catechin dimer, procyanidin B-3, Biosci. Biotechnol. Biochem., 66, 1764, 2002. 

Figure 2, Principal naturally occurring dimeric procyanidins.

Garcia-Ramirez B, Fernandez-Larrea J, Salvado MJ, Ardevol A, Arola L, Blade C. 2006. Tetramethylated dimeric procyanidins are detected in rat plasma and liver early after oral administration of synthetic oligomeric procyanidins. J Agric Food Chem 54 2543-2551. 

Zhu QY, Holt RR, Lazarus SA, Ensunsa JL, Hammerstone JF, Schmitz HH, Keen CL. 2002. Stability of the flavan-3-ols epicatechin and catechin and related dimeric procyanidins derived from cocoa. J Agric Food Chem 50 1700-1705. 

Mackenzie GG, Delfino JM, Keen CL, Fraga CG, Oteiza PI. 2009. Dimeric procyanidins are inhibitors of NF-kB-DNA binding. Biochem Pharmacol, in press (doi 10.1016/j.bcp.2009.06.111). 

Procyanidin B3 (= Catechin (4a —>8) catechin) (procyanidin dimer) Procyanidin B4 (catechin (4a — 8)epicatechin) (procyanidin dimer) Tellimagrandin I (= 4,5 Hexahydroxydiphenoyl 2,3-digalloylglucose) (ellagitannin)... 

Mescaline (=Mezcaline 3,4,5-Trimethoxy-phenethylamine) (phenylethylamine) A-Methylmescaline (= A -Methylmezcaline 7 1Methyl-3,4,5-trimethoxy-phenethylamine) (phenylethylamine) Procyanidin B2 (= Epicatechin (4(3 —>8) epicatechin) (procyanidin dimer) Procyanidin B3 (= Catechin (4a—>8) catechin (procyanidin dimer)... 

FIGURE 3.3 Structures of (a) flavonols, (b) flavan-3-ols and (c) the dimeric procyanidin Bl, occurring in grapes and berry fruits. [Source Adapted from Spanos and Wrolstad (1992).]... 

Figure 2.20 Chromatogram relative to analysis of dimer procyanidins in the skins extract (fraction ethyl acetate from C18 cartridge) (sample volume injected 10p,L). 1. procyanidin Bl, 2. procyanidin B3, 3. procyanidin B2...

Kiehne et al. [282] who analyzed green tea using a thermospray interface in the positive ionization mode could distinguish fragments originating form upper (T) and lower (B) units of dimeric procyanidins. Cleavage of the interflavanoid bond resulted in a carbenium-ion (T-l) and a neutral fragment from the lower unit which could be protonated under the experimental conditions to form a pseudo molecular ion (B + H+). 

After treatment with the VP reagent, Lespedezae herba (5a. 6b) shows the phenolic compounds as red-brown zones (vis.). In addition to free catechin, epicatechin (R, -0,9), the dimeric procyanidins migrate into the upper R, range and trimeric procyanidins are found in the lower R, range. 

The crude drug of H. perforatum contains approx. 8% of tannins of the proanthocyanidin-type [92]. These proanthocyanidins are constituted of catechin and epicatechin units since acid hydrolysis results exclusively in cyanidin [2]. Melzer isolated and characterised the dimeric procyanidin B2 50, further procyanidins of a higher degree of polymerisation also found were not fully identified [93]. 

Dimeric procyanidins may be divided into two categories, identified by a letter of the alphabet and a number (Weinges et al, 1968 Thompson et al., 1972) ... 

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