Ellagitannins and red raspberries
Prior to the research on pomegranates and ellagitannins research was being performed on the use of red raspberries for their health and anticancer benefits. The summary points are that the whole fruit, the mixture of a variety of phytonutrients provides the benefits and that an isolated singe phytonutrient may be less bioavailable and less bioactive - less chemically likely to provide benefits as the mixture of phytonutrients that the whole food provides. An article from 2001 discusses this in more detail and mentions that early work on pomegranates suggested they would be an even better source of the group of ellagitannins and other polyphenols.
The compounds when working together within the body seem to help make cancer cells stop dividing and start dying by apoptosis like normal cells would - and without having any toxic effects on other normal healthy cells. The ellagitannins and other phytonutrients in red raspberries also seemed to prevent precancerous cells from becoming cancerous - dividing at above average rate of growth.
Other health benefits of the whole fruit used as a fruit puree equivalent to eating one cup of red raspberries per day, providing 40 mg of ellagitannins, included:
"European medical studies also demonstrate that red raspberry ellagitannins lower the incidence of birth defects, promote wound healing, reduce heart disease, and may reduce or reverse chemically induced liver fibrosis. In addition, the ellagic acid produced from the ellagitannins has anti-bacterial and anti-viral properties."
Read more: The Truth About Ellagic Acid and Red Raspberries, https://jonbarron.org/article/truth-about-ellagic-acid-and-red-raspberries
Ellagitannins and pomegranates was a discussion begun in a previous post: Pomegranate polyphenols and Microglia M2 Activation. I didn't include the information in my summary but one of the links mentions that whole pomegranate juice / juice made with the peel / provides about 2 grams per liter of ellagitannins which would be many times more than 40 milligrams. Two grams would be 2000 milligrams and a liter is slightly less than a quart which is four cups, so roughly the whole pomegranate juice/extract is providing 500 milligrams per cup. A cup of juice would be more concentrated, being a liquid, compared to a cup of loosely packed whole red raspberries with seeds and air space, so a cup of raspberry puree or red raspberry juice would likely provide more than 40 milligrams.
Black raspberries are a dark purple color were not mentioned in the 2001 article but a more recent study on cancer therapy from 2016 mentions them as a source of ellagic acid so they may have an equivalent amount of the beneficial phytonutrients.
Read more: Black raspberries in cancer clinical trials: Past, present and future. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5008867/
Blueberries and blackberries and other berries are good sources of a variety of beneficial phytonutrients. Many types have the most prevalent phytonutrients listed and extraction methods that are typically used for commercial products are discussed in this research review: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5384171/
A shorter article discussing phytonutrients found in blueberries, blackberries and raspberries in a more general way: http://berryhealth.fst.oregonstate.edu/symposium/lukehowardabstract.htm
Disclaimer: Opinions are my own and the information is provided for educational purposes within the guidelines of fair use. While I am a Registered Dietitian this information is not intended to provide individual health guidance. Please see a health professional for individual health care purposes.