Procyanidin dimers and trimer

Thermodynamic analysis of the binding constants of BSA and procyanidin dimer and trimer from the Van t Hoff equation (29) indicates a reaction with a positive entropy change, a positive... 

Ricardo DS, Rigaud JM, Cheynier V et al (1991) Procyanidin dimers and trimers from grape seeds. Phytochemistry 30 1259-1264... 

Verstraeten SV, Hammerstone JF, Keen CL, Fraga CG, Oteiza PI. 2005. Antioxidant and membrane effects of procyanidin dimers and trimers isolated from peanut and cocoa. J Agric Food Chem 53 5041-5048. 

Cranberries have been used traditionally for the treatment and prevention of urinary tract infections. Their effectiveness was demonstrated by a randomized, double-blind placebo-controlled trial (Avom et ah, 1994). Escherichia coli are the principal bacterial species responsible for urinary tract infection. The consumption of cranberry juice reduced the adherence of E. coli to the uroepithelial bladder cells in healthy human volunteers (Di Martino et ah, 2006). A-type procyanidin dimers and trimers that were isolated from cranberries were found to inhibit the adherence of uropathogenic E. Coli, whereas (—)-epicatechin and a B-type dimer were not effective (Foo et ah, 2000). 

Ricardo da Silva, J. M., Rigaud, J., Cheynier, V, Cheminat, A., Moutounet, M. (1991c). Procyanidin dimers and trimers from grape sesds.Phytochemistry, 30, 1259-1264. 

Flavan-3-ols, often known as catechins (Fig. 11.16 of Chapter 11), are widely distributed. The most widely distributed members of this class of compounds are catechin [(+ )-(2/ ,35)-catechin] (2,3-trans) (3) and epicatechin [(-)-(2i ,3/ )-epicatechin] (2,3-cis) (30) (Fig. 12.1) which usually occur as free aglycones and not as glycosides. The known (2/ ,3S)-proanthocyanidins are tabulated by Porter (1988). The enantiomeric compounds are e f-catechin [(— )-(25,3/ )-catechin] 2,3-trans) and enf-epicatechin [( + )-(25,35)-epicatechin] (2,3-m). Some 2S-flavan-3-ols are found free and as gallate esters in plants (Stafford, 1989). Tissues that contain flavan-3-ols often contain procyanidin dimers and trimers (Haslam, 1975). Some flavan-3-ol com-... 

Narayanan V, Seshadri T R 1969 Chemical components of Acer rubrum wood and bark Occurrence of procyanidin dimer and trimer. Indian J Chem 7 213-214... 

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]. 

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. 

Sun B, Belchior P, Ricardo-da-SUva JM et al (1999) Isolation and purification of dimeric and trimeric procyanidins from grape seeds. J Chromatogr A 841 115-121... 

Even if dimers and trimers are stable under GIT conditions and absorbed in their native form as seen for the monomers, the amount crossing the epithelial barrier of the small intestine and being further excreted in urine must be very low. The major part of the ingested procyanidins must reach the colon where an abundant microflora can metabolize them into smaller molecules, which are more readily absorbed. The general absorption and metabolism pathways of procyanidin monomers to oligomers in the GIT, from their ingestion to microbial metabolism, are summarized in Figure 2.5. 

The red zones maybe due to dimeric and trimeric procyanidines, a biflavonoic catechiii-taxifolin, catechin and gallotannins. 

Analysis of these molecules is particularly complex, due to the great structural diversity resulting from the number of hydroxyl groups, their position on the aromatic nuclei, the stereochemistry of the asymmetrical carbons in the pyran cycle, as well as the number and type of bonds between the basic units. In spite of the progress made in liquid chromatography, mass spectrometry and NMR, all of the structures have not been analyzed only the procyanidin dimers and some of the trimers have been completely identified. 

HPLC analysis of the development of dimeric and trimeric procyanidins, as well as simple flavanols, extracted from the skins and seeds of red and white grapes, shows that concentrations decrease to a greater or lesser extent, but never increase (de Freitas, 1995). It has been observed that procyanidin B2 is the most common dimer in ripe Merlot and Cabernet Sauvignon (Table 6.11), followed by trimeric Ci. All the dimers are present in the seed extract, whereas procyanidins B4,... 

Bv and Bg are absent from the skins. Red and white grape seeds have similar distributions of procyanidins. On the other hand, dimer B2 is in the majority in red grape skins, but practically absent from white grapes, where it is replaced by Bi. These results show that dimeric and trimeric procyanidins, present in very low concentrations, are not the most important phenolic compounds in grapes. 

The structures of procyanidins 35-38 were assigned on a basis of H-NMR spectra of the decaacetates. The absolute stereochemistry has been determined as (45) for compounds (38) and (36) and (4/ ) for compounds (37) and (35). Mixtures of these particular dimers have not been found, but other dimers and trimers have been detected with them (Hillis, 1985 Porter, 1988). C-NMR spectra are especially useful for analyses of these compounds because a pronounced 7 effect (— 4.5 ppm) is observed and the chemical shift of C-2 is dependent on the orientation of the substituent at C-4 of the flavan system. All major natural procyanidin dimers possess a /ra/w-orientation of the hydroxyl group at... 

The reported LODs and LOQs for procyanidins (catechin, epicatechin, dimer, and trimer) in plasma samples that were lower than 4 and 10 nM, except for the trimers, which were 800 and 980 nM, respectively, using the off-line SPE-UHPLC-MS/MS [31], Similar results were obtained when the off-line iSPE-UHPLC-MS/ MS was used to analyze these procyanidin compounds in the biological sample [33]. This demonstrated the high capacity of the pSPE sample pretreatment technique, where the LODs and LOQs were similar in comparison with SPE. In contrast, the preconcentration factor obtained in SPE was 10, in comparison with obtained in pSPE, which was 3.5. 

Then, different procyanidin metabolites were generated, these being catechin and epicatechin in its glucuronide forms, catechin and epicatechin in its sulfate forms, methyl-catechin and methyl-epicatechin in its glucuronide forms, and methyl-calechin and methyl-epicatechin in its sulfate forms [31-33,35-39], In some studies, the aglycones, catechin, epicatechin, dimer, and trimer were also identified [31,33,35,36]. The main metabolites generated from the procyanidin-rich extract intake are shown in Table 14.3. 

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