Proanthocyanidins degradation

The chemical characteristics of the proanthocyanidins were elucidated by total oxidation and partial degradation in the presence of phloroglucinol followed by HPLC analysis. The native extract of proanthocyanidins contained (+) gallocatechin, (-) epigallocatechin, (h-) catechin, and (-) epicatechin units. ... 

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]. 

The report on aesculitannins A-G from the seed shells of Aesculus hippocastanum demonstrates three important chemical methods to facilitate the unequivocal structural elucidation of the A-type proanthocyanidins. These protocols include thiolytic degradation using phenylmethanethiol in acidic medium, oxidative formation of the ether linkage when... 

Gu, L. et al.. Screening of foods containing proanthocyanidins and their structural characterization using LC-MS/MS and thiolytic degradation, J. Agric. Food Chem., 51, 7513, 2003. 

Evidence occurred that polymeric proanthocyanidins could be degraded by the colonic microflora into low-molecular-weight compounds, which would be subsequently absorbed. The group of Deprez... 

It is important to monitor the time that the proanthocyanidin is allowed to react with the phloroglucinol solution. The products formed are not stable under acidic conditions, and it is therefore critically important that the reaction not exceed 20 min. Of particular concern are the flavan-3-ol monomers, which degrade more rapidly than the phloroglucinol adducts (Kennedy and Jones, 2001). Excessive degradation of the flavan-3-ol monomers will result in reduced amount of terminal subunits. This in turn will reduce the conversion yield and increase the average degree of polymerization calculated. 

Proanthocyanidins are very susceptible to oxidative degradation. To minimize subsequent oxidation, proanthocyanidins should be stored protected from light and under freezer conditions (-20°C or cooler). 

RG Bailey, HE Nursten, I McDowell. A comparison of the HPLC, mass spectra, and acid degradation of theafulvins from black tea and proanthocyanidin polymers from wine and cider. J Sci Food Agric 64 231-238, 1994. 

Controlled acid-catalyzed degradation of the proanthocyanidins in grape seeds with L-cysteine as the capture nucleophile, gave a series of mono-, di-, and tri-meric-L-cysteine complexes. The flavan-3-ol adducts included the L-cysteine derivatives (173), (174), and (175) of epicatechin (3), catechin (2), and epigallocatechin, respectively. The dimers comprise the derivatives of procyanidin B-2 (176) and its C-ring... 

Acid degradation is widely used to identify proanthocyanidins. In solutions of mineral acids proanthocyanidins are cleaved to form carbocations from their "upper units" and flavan-3-ols from their "lower unit". The carbocations are immediately converted to anthocyanidins by... 

Some derivatization reactions which are frequently used for the structural elucidation of procyanidins have been adopted for HPLC analysis. Koupai-Abyazani et al. [231] developed a qualitative HPLC procedure to separate flavan-3-ol monomers and phloroglucinol adducts. The reaction is based on the acid degradation of procyanidins in the presence of phloroglucinol. The procedure has been used for quantitation of polymeric proanthocyanidins from sainfoin leaves [63]. HPLC analysis of benzylthioethers after acid degradation of procyanidins in the presence of toluene-a-thiol has so far only been used for qualitative analysis [250-251],... 

The metabolism of procyanidins by incubated human colonic microflora has been studied in vitro under anoxic conditions, using nonlabeled and " C-labeled purified proanthocyanidin polymers [102]. Interestingly, the oligomers were almost totally degraded after 48 h of incubation, and meta- or para-monohydroxy-lated-phenylacetic, phenylpropionic, and phenylvaleric acids were identified as metabolites, providing the first evidence that dietary flavan-3-ol polymers can be degraded to low-molecular-weight aromatic compounds in the body [102]. 

Abia R, Fry SC. Degradation and metabohsm of c-labeUed proanthocyanidins from carob ceratonia siliqua) pods in the gastrointestinal tract of the rat. J Sci Food Agric 2001 81(12) 1156-1165. 

The constitution of the polymers isolated in this way may be readily deduced from the NMR spectrum in acetone-water (25) or methanol (126), or by a combination of chemical degradation and chiroptical methods (25). The most convenient of these is a NMR spectrum of the proanthocyanidin, which gives... 

One fungus isolated from a rotting log of Pinus radiata has been shown to be capable of growth on proanthocyanidins as a sole carbon source. Grant (44) identified it as the filamentous fungus Penicillium adametzi- Similarly, Deschamps and Leulliette (27) have isolated a number of yeasts from decaying bark that degrade both hydrolyzable and condensed tannins. 

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