Depolymerization of proanthocyanidins in the presence of phloroglucinol
or benzyl mercaptan
nucleophiles was studied to develop a method for their quantitative
determination. Degradation
products were separated and quantified by either GC or HPLC and the
reaction conditions optimized.
The high depolymerization yields obtained with benzyl mercaptan
make the method suitable for
proanthocyanidin determination. The method is more specific and
sensitive than the colorimetric
methods classically used. It is particularly well suited for the
analysis of samples containing either
low amounts of proanthocyanidins or insoluble
proanthocyanidins.
Keywords: Proanthocyanidins; tannins; estimation; thiolysis;
phloroglucinol
Eight ellagitannins from Quercus robur L. wood have been studied by high-resolution 'H and 13C NMR and FAB-MS spectroscopy. Three of these polyphenols are known compounds, namely, castalagin, vescalagin, and grandinin. Five of the ellagitannins are new oligomeric compounds containing vescalagin or castalagin moieties bonded to a pentose, lyxose or xylose. The inter-unit linkages are carbon-carbon bonds between C-I of the glucosyl residue of one unit and either the C-2' of the hexahydroxydiphenoyl (HHDP) group of a second unit or the C-I of a pentosyl sugar.
40.1989, pp. 95-96.
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