A metabolite of ellagic acid found in pomegranates may inhibit an enzyme called aromatase that converts androgen to oestrogen, and that also plays a key role in the development of breast cancer, according to findings published in Cancer Prevention Research.
Researchers from the City of Hope in Duarte, California and the University of California, Los Angeles said they were surprised by their findings. “We previously found other fruits, such as grapes, to be capable of the inhibition of aromatase. But, phytochemicals in pomegranates and in grapes are different,” said principal investigator Shiuan Chen, PhD.
Pomegranate, a rich source of antioxidants, has been linked to improved heart health, but a growing body of science indicates the fruit protect against prostate cancer. Studies have also reported a role in joint health by slowing cartilage loss in arthritis.
It is these antioxidants, and particularly ellagitannin compounds like punicalagins and punicalins, which accounts for about half of the fruit's antioxidant ability, that are reportedly behind the proposed health benefits.
Note of caution
Commenting independently on the findings, Professor Gary Stoner from Ohio State University said additional studies will be needed to confirm these initial findings.
“This is an in vitro study in which relatively high levels of ellagitannin compounds were required to demonstrate an anti-proliferative effect on cultured breast cancer cells,” said Stoner. “It's not clear that these levels could be achieved in animals or in humans because the ellagitannins are not well absorbed into blood when provided in the diet.”
Chen and his co-workers screened 10 ellagitannin-derived compounds from pomegranates, including ellagic acid, gallagic acid, and urolithins A and B against a breast cancer cell line. According to the researchers, ellagitannin are converted to ellagic acid in the body, and this is then converted to urolithins by gut microflora.
The results showed that urolithin B was the most potent inhibitor of breast cancer cell growth at doses of 2.35 and 4.7 micromoles per litre in the in-cell assay.
“The ingestion of pomegranate juice can lead to concentrations of circulating urolithins reaching up to 18 micromoles per litre in blood,” said the researchers. “Taken together with the results of current studies and reports of the presence of urolithin A and urolithin B in the blood and urine of human subjects following pomegranate ingestion, the results of these analyses suggest that pomegranate intake may be a viable strategy for the chemoprevention of breast cancer.”
Powel Brown from University of Texas M. D. Anderson Cancer Center echoed Stoner's sentiments and called the results “intriguing”.
“More research on the individual components and the combination of chemicals is needed to understand the potential risks and benefits of using pomegranate juice or isolated compounds for a health benefit or for cancer prevention,” said Brown. “This study does suggest that studies of the ellagitannins from pomegranates should be continued.”
Until then, Stoner said people “might consider consuming more pomegranates to protect against cancer development in the breast and perhaps in other tissues and organs”.
The study was supported by the National Institutes of Health.
Source: Cancer Prevention Research
Publishedonline ahead of print, doi: 10.1158/1940-6207.CAPR-08-0225
“Pomegranate Ellagitannin–Derived Compounds ExhibitAntiproliferative and Antiaromatase Activity in Breast Cancer Cells In vitro”
Authors: L.S. Adams, Y. Zhang, N.P. Seeram, D. Heber, S. Chen