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J Agric Food Chem. 2015 Jul 29;63(29):6555-66. doi: 10.1021/acs.jafc.5b02062. Epub 2015 Jul 17.

Validated Method for the Characterization and Quantification of Extractable and Nonextractable Ellagitannins after Acid Hydrolysis in Pomegranate Fruits, Juices, and Extracts.

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†Research Group on Quality, Safety and Bioactivity of Plant Foods, CEBAS-CSIC, P.O. Box 164, 30100 Campus de Espinardo, Murcia, Spain.
§Fisheries and Aquaculture Research, Nofima - Norwegian Institute of Food, Osloveien 1, NO-1431 Ås, Norway.
#TÜBİTAK Marmara Research Center, Food Institute, Gebze-Kocaeli, Turkey.
⊥Food and Environmental Sciences, Division of Food Chemistry, P.O. Box 27, 00014 University of Helsinki, Finland.
ΔVITO - Flemish Institute for Technological Research, Boeretang 200, 2400 Mol, Belgium.
ΠFood and Health Programme, Institute of Food Research, Norwich Research Park, Norwich NR4 7UA, United Kingdom.


Pomegranates are one of the main highly valuable sources of ellagitannins. Despite the potential health benefits of these compounds, reliable data on their content in pomegranates and derived extracts and food products is lacking, as it is usually underestimated due to their complexity, diversity, and lack of commercially available standards. This study describes a new method for the analysis of the extractable and nonextractable ellagitannins based on the quantification of the acid hydrolysis products that include ellagic acid, gallic acid, sanguisorbic acid dilactone, valoneic acid dilactone, and gallagic acid dilactone in pomegranate samples. The study also shows the occurrence of ellagitannin C-glycosides in pomegranates. The method was optimized using a pomegranate peel extract. To quantify nonextractable ellagitannins, freeze-dried pomegranate fruit samples were directly hydrolyzed with 4 M HCl in water at 90 °C for 24 h followed by extraction of the pellet with dimethyl sulfoxide/methanol (50:50, v/v). The method was validated and reproducibility was assessed by means of an interlaboratory trial, showing high reproducibility across six laboratories with relative standard deviations below 15%. Their applicability was demonstrated in several pomegranate extracts, different parts of pomegranate fruit (husk, peels, and mesocarp), and commercial juices. A large variability has been found in the ellagitannin content (150-750 mg of hydrolysis products/g) and type (gallagic acid/ellagic acid ratios between 4 and 0.15) of the 11 pomegranate extracts studied.


acid hydrolysis; ellagic acid; ellagitannin; interlaboratory reproducibility; pomegranate

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