Reactions of polyphenols in pomegranate peel with nitrite under simulated stomach conditions.

Punicalagin and ellagic acid are the major polyphenols present in pomegranate peels. The contents of α-punicalagin, β-punicalagin, and ellagic acid in the pomegranate peels were approximately 75, 72, and 20 µM, respectively. The reactions of polyphenols in pomegranate peels with sodium nitrite under simulated stomach conditions were studied. The reactions decreased the polyphenolic contents of the pomegranate peels and accompanied the formation of nitroso compounds. The oxidation rates followed the order ellagic acid ＜α-punicalagin ≈ β-punicalagin. The results suggested that the reactions can occur in the stomach after a meal, while the pH changes from 2 to 4.5.