Ellagitannins are phytochemicals present in many fruits and nuts, such as pomegranate, raspberries and almonds. Ellagitannins are polyphenols, which hydrolyse into ellagic acid
. The main ellagitannin present in pomegranate juice is punicalagin. In-vitro studies have shown that the ellagitannins from pomegranate juice have many health promoting benefits, but these are of little use if the ellagitannins are not absorbed. Pomegranate extract have been shown to inhibit the proliferation of human cancer cells and to cause cancer cell apoptosis. The aim of this study was to determine the absorption and metabolism of ellagitannins from pomegranate juice on 18 healthy volunteers. The volunteers received a single dose of about 200 ml pomegranate juice and afterwards their urine and blood samples were taken and analysed. The researchers found ellagic acid in the serum and metabolites in the urine. The ellagic acid levels in serum increased within hours but disappeared rather quickly. The ellagic acid metabolite dimethylellagic acid glucuronide seemed to be a good indicator of intake of ellagic acid, because it was found in 15 of the 18 volunteers and within 1 day or intake of pomegranate juice. In addition, the microbiological metabolite urolithin-glucoronide was found in the urine. Urolithin may also have biological effects and may be partially responsible for the health benefits of pomegranate. Further studies are required to determine cause of absence of urolithin in some of the volunteers.
Source: Seeram NP, Henning SM, Zhang Y, Suchard M, Li Z and Heber D. Pomegranate Juice Ellagitannin Metabolites Are Present in Human Plasma and Some Persist in Urine for Up to 48 Hours. Journal of Nutrition. 136:2481-2485, October 2006