Many fruits and vegetables get their color from chemical compounds called anthocyanins. Based on experiments using rats and human colon cancer cells, a new study suggests that anthocyanins may be able to slow the growth of colon cancer cells. Hopefully, this will help scientists understand what gives fruits and vegetables their cancer-fighting properties as well as how better to use these properties to fight disease.

Monica Giusti, the lead author of the study and an assistant professor of food science at Ohio State University, presented the findings of her team at the August 19, 2007 national meeting of the American Chemical Society in Boston.

Giusti and her team found that slight alterations in the structure of anthocyanin molecules could make these compounds much more potent as anti-cancer agents.

Using human colon cancer cells grown in the laboratory, the researchers tested the anti-cancer effects of anthocyanin-rich extracts from a variety of fruits and vegetables. They retrieved these anthocyanins from a wide range of plants, including grapes, radishes, purple corn, chokeberries, bilberries, purple carrots and elderberries. The plants were selected for their extremely deep colors, which indicate a high anthocyanin content.

The researchers also exposed different plant extracts to colon cancer cells. They then used biological tests to determine the number of cancer cells left after anthocyanin treatment.

The results? While all anthocyanins were effective, their cancer-fighting properties varied depending on their source. Anthocyanin derived from purple corn was the most potent. Chokeberry and bilberry extracts were nearly as potent as purple corn. Radish extract proved the least potent.

"All fruits and vegetables that are rich in anthocyanins have compounds that can slow down the growth of colon cancer cells, whether in experiments in laboratory dishes or inside the body," Giusti said.

In animal studies, rats with colon cancer cells were fed a daily diet of anthocyanin extracts either from bilberries and chokeberries, which are most often used as flavorings or to make jams and juices. The dietary addition of the anthocyanin extracts reduced signs of colon tumors by 70 and 60 percent, respectively.

Giusti says the results suggest that anthocyanins may protect against certain gastrointestinal cancers.

"Very little anthocyanin is absorbed by the bloodstream," Giusti said. "But a large proportion travels through the gastrointestinal tract, where those tissues absorb the compound."

Giusti stops short of recommending one kind of fruit or vegetable over another. She and her colleagues are continuing to study the chemical structure of anthocyanins and how the body uses these compounds.

"There are more than 600 different anthocyanins found in nature," she said. "While we know that the concentration of anthocyanins in the GI tract is ultimately affected by their chemical structures, we're just beginning to scratch the surface of understanding how the body absorbs and uses these different structures."