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J Agric Food Chem. 2006 Jun 14;54(12):4469-75.

Concentration and mean degree of polymerization of Rubus ellagitannins evaluated by optimized acid methanolysis.

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1
IASMA Research Center, Agrifood Quality Department, Via E. Mach 1, 38010 San Michele all'Adige, Italy.

Abstract

Ellagitannins are a major class of phenolics largely responsible for the astringent and antioxidant properties of raspberries and blackberries. The Rubus ellagitannins constitute a complex mixture of monomeric and oligomeric tannins. Rubus oligomeric ellagitannins contain, beside the well-known ellagic acid and gallic acid moieties, the sanguisorboyl linking ester group. When exposed to acids or bases, ester bonds are hydrolyzed and the hexahydroxydiphenic acid spontaneously cyclizes into ellagic acid. This study describes a new, rapid procedure for the acid hydrolysis of Rubus ellagitannins in methanol, which results in maximal yield and enables the quantification of all the major reaction products. Additionally, the method provides the rationale for estimating the mean degree of polymerization of Rubus ellagitannins.

PMID:
16756382
DOI:
10.1021/jf060404w
[Indexed for MEDLINE]
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