Procyanidin oligomers

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]. 

Arteel and Sies (1999) examined procyanidin oligomers of different size, isolated from the seeds of Theobroma cacao, for their ability to protect against nitration of tyrosine. Serraino and others (2003) investigated antioxidant activity of the blackberry juice and cyanidin-3-O-glucoside on endothelial dysfunction in cells and in vascular rings exposed to peroxynitrite. However, more work is needed in this area, and the confounding effects of oxidized protein/amino acids in the diet need to be elucidated. 

Heat-denatured Gl exhibited a surface hydrophobicity greater than that of native Gl. The increase was not unexpected since hydrophobic groups are commonly oriented towards the center of proteins in aqueous solvents. Heat denaturation of protein exposes hydrophobic groups to the solvent. Binding of denatured Gl to bean procyanidin oligomer was predominantly hydrophobic. 

Fig. 2.113. Structures of monomeric flavan-3-ols and procyanidin oligomers in apples. Reprinted with permission from A. Yanagida et al. [253].

Fig. 2.115. Mass chromatograms of catechin monomers (m/z 289) and procyanidin oligomers (dimer through hexamers m/z 577 to 1729). C, ( + )-catechin, EC, ( — )-epicatechin, and PB2, procyanidin B2 as identified by the retention times of authentic standard. Reprinted with permission from J. Wollgast et al. [256].

Balas, L. and Vercauteren, J., Extensive high-resolution reverse 2D NMR analysis for the structural elucidation of procyanidin oligomers. Magn. Reson. Chem. 32, 386, 1994. 

Recently, chocolate and cocoa have gained interest because of their contents of catechins and related polymers (procyanidin oligomers) [52]. 

Zhu QY, Holt RR, Lazarus SA, Orozco TJ, Keen CL. 2002. Inhibitory effects of cocoa flavanols and procyanidin oligomers on free radical-induced erythrocyte hemolysis. Exp Biol Med (Maywood) 227 321-329. 

Procyanidin oligomers [(4a) n = 0 to 10] apparently possess mainly linear conformations, compared with the proven angularity of profisetinidin and prorobinetinidin analogues (2) and (3). 

In summary, the diol-phase column had better separation resolution for procyanidin oligomers than the silica column. Limits of quantitation in the diol-phase method were significantly lower than those in the silica... 

Hellstrom, J.K. Sinkkonen, J. Karonen, M. Mattila, P. 2006. Isolation and Structure elucidation of procyanidin oligomers from saskatoon berries (Amelanchier alni-folia). J. Agric. Food Chem. 55 157-164. 

Shoji, T. Masumoto, S. Moriichi, N. Akiyama, H. Kanda, T. Ohtake, Y. Goda, Y. 2006. Apple procyanidin oligomers absorption in rats after oral administration analysis of procyanidins in plasma using the porter method and high-performance... 

Q. Y. Zhu, R. R. Holt, S. A. Lazarus, T. J. Orozco and C. L. Keen. Inhibitory effects of cocoa ftavanols and procyanidins oligomers on free radical-induced erythrocyte hemolysis. Experimental Biology and Medicine 227 (2002) 321 -329. 

In order to correlate these pharmaceutical activities with their degree of polymerization, it is necessary to establish an efficient, reliable separation method. However, the application of liquid chromatography to the separation of these procyanidin oligomers is difficult because the oligomers above hexamers tend to cause irreversible adsorption onto the column packing materials. 

The CCC separation of procyanidin oligomers from apple condensed tannin was performed using a type-J highspeed CCC centrifuge (Fig. 1). The apparatus holds a multilayer coiled separation column and counterweight symmetrically at a distance of 10 cm from the central axis of the centrifuge. The separation column is fabricated by... 

As the chromatographic process in CCC is based on the partition of a solute between the mobile and stationary phases, the value is the most important parameter in CCC. A Ad value of around 1.0 is most desirable in CCC, wherein a solute with Ad =1.0 elutes with its retention volume equivalent to the total column capacity. In the above two-phase solvent systems, the Ad values of monomers (catechin and/or epicatechin) were greater than 1.0, and those of the ACTs are always smaller than 1.0, suggesting that monomers are more hydrophobic than their oligomers present in ACTs. Among these four solvent systems, we selected a simple binary system of methyl acetate/water for the separation of procyanidin oligomers from ACTs by CCC. 

These results indicate that the present method is capable of fractionating the apple procyanidin oligomers from ACTs according to the degree of polymerization. The highly polymerized, very hydrophilic oligomers, which tend to be adsorbed on the column packing materials by HPLC, were aU recovered from the CCC column. 

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