Lee Swanson Research Update

Pomegranate Extracts May Inhibit Prostate Cancer Growth

September 2007

Ellagitannins from pomegranate tend to accumulate in the prostate and may be behind the reported benefits of the fruit, a new animal study suggests.

The study, published in the Journal of Agricultural and Food Chemistry, also reports that the growth of prostate cancer cells was significantly inhibited by the pomegranate ellagitannins and their metabolites, highlighting the potential of the extracts against the disease.

"We have shown that pomegranate ellagitannins are concentrated to a high degree in mouse prostate tissues," wrote the authors, led by Navindra Seeram. "The current study contributes to the increasing body of evidence demonstrating the prostate cancer chemopreventive potential of pomegranate ellagitannins."

The fruit, a rich source of antioxidants, has been linked to improved heart health, but other varied claims have been made including protecting against prostate cancer and slowing cartilage loss in arthritis. It is the antioxidants, and particularly compounds like punicalagin, accounting for about half of the fruit's antioxidant ability, that are behind the proposed anti-cancer effects observed in the study.

The new study, by researchers from the University of California at Los Angeles, suggests that the ellagitannins may also play a role in prostate cancer protection.

Seeram and coworkers looked at the ability of ellagitannins and their metabolites to accumulate in the tissues in male mice. According to the researchers, ellagitannins are hydrolyzed to release ellagic acid, which is then converted by gut microflora to urolithin A derivatives.

"It is unclear why pomegranate ellagitannin metabolites localize at higher levels in prostate, colon and intestinal tissues relative to the other organs studied," wrote the authors. "Importantly, the predilection of bioactive pomegranate metabolites to localize in prostate tissue, combined with clinical data demonstrating the anticancer effects of pomegranate juice, suggest the potential for pomegranate products to play a role in prostate cancer chemoprevention," they added.

The researchers also investigated the potential of pomegranate extract to inhibit the growth of prostate cancer cells grafted onto mice with impaired immune function. Compared to the control, the pomegranate extract was found to significantly inhibit the growth of the grafter tumors.

Journal of Agricultural and Food Chemistry, published online ahead of print

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