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flavonoids, phenolic acids and proanthocyanidins, but much less on
ellagitannins. This is probably due to the fact that − according to the
current knowledge − the occurrence of ellagitannins and ellagic acid in
commonly consumed foods is limited to a few berry, fruit and nut
species and oak-aged wines (Clifford and Scalbert, 2000). This chapter
complements the previous one and summarises the research data on
ellagitannins and ellagic acid in the human diet, while outlining the
current evidence on the potential health benefits of foods and beverages
rich in ellagitannins.
8.2 Ellagitannins and Ellagic Acid in Foods
8.2.1 Analytical methods
Ellagitannins are complex derivatives of ellagic acid. They contain one
or more hexahydroxydiphenic acid (HHDP) moieties esterified to a
polyol, usually glucose (Clifford and Scalbert, 2000). Hydrolysis of
ellagitannins with acids or bases yields HHDP, which is spontaneously
lactonized to ellagic acid (Fig. 8.1). This reaction has been commonly
utilized for the detection and quantification of food ellagitannins as
ellagic acid equivalents by HPLC after acid hydrolysis ( e.g. , Daniel et
al ., 1989, Häkkinen et al. , 2000, Lee and Talcott, 2004, Vrhovsek et al. ,
2006, Koponen et al. , 2007). Since food samples also contain small
amounts of free ellagic acid and its glycosides, these should be analyzed
without hydrolysis and subtracted from the total ellagic acid value to
obtain the true content of ellagitannins.
O
HO
O
HO
OH
O
OH
O
Fig. 8.1 Ellagic acid, the hydrolysis product of ellagitannins. Food ellagitannins can be
quantified as ellagic acid equivalents after acid hydrolysis.
 
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