Extraction, stability, and quantitation of ellagic acid in various fruits and nuts

Abstract This study was undertaken to determine the amount of ellagic acid, a naturally occurring inhibitor of carcinogenesis, in various fruits and nuts. Ellagic acid was extracted from freeze-dried berries, pears, peaches, plums, grapes, apples, kiwi, and several nuts using either acetone/water or methanol. The extracts were treated with trifluoroacetic acid to hydrolyze the ellagic acid glucosides, and analyzed by high-performance liquid chromatography (HPLC). Both acetone/water and continuous soxhlet extraction with methanol were equally effective in extracting ellagic acid from strawberries. In raspberries, the amount of ellagic acid liberated by the two extraction methods was not significantly different after hydrolysis with trifluoroacetic acid. The extracts were stable over 90 days at −20, 4, and 25°C. Analysis showed that every food sample tested contained ellagic acid, but only the amounts present in strawberries (630 μg), raspberries (1500 μg), blackberries (1500 μg), walnuts (590 μg), pecans (330 μg), and cranberries (120 μg ellagic acid/g dry wt) were within the calibration range of the assay. In strawberries, 95.7% of the ellagic acid was found in the pulp while 4.3% was contained in the seeds. The seeds of raspberries contained 87.8% of the ellagic acid, and 12.2% was present in the pulp. The juice of both fruits contained negligible amounts of ellagic acid.