food chemistry

Pigments in tomatoes pack a punch

U. ILLINOIS (US) — Tomatoes have previously been found to reduce the risk of prostate cancer and now scientists have developed a tool that will help find out why.

“Scientists believe that carotenoids—the pigments that give the red, yellow, and orange colors to some fruits and vegetables—provide the cancer-preventive benefits in tomatoes, but we don’t know exactly how it happens,” says John Erdman, professor of human nutrition at the University of Illinois.

Researchers will use isotopic labeling of three tomato carotenoids with heavier carbon atoms than are commonly seen in nature, which will allow tracking of the tomato components’ absorption and metabolism in the body.

“We have two questions we’d like to answer,” Erdman says. “First, are the carotenoids themselves bioactive, or are their metabolic or oxidative products responsible for their benefits? Second, is lycopene alone responsible for the tomato’s benefits, or are other carotenoids also important?”

The study is published in the Journal of Agricultural and Food Chemistry.

Previous animal studies have shown that whole tomato powder, which contains all of the fruit’s nutritional components, is more effective against prostate cancer than lycopene alone.

“Lycopene, which gives the fruit its red color, has received a lot of attention—it’s even advertised as an ingredient in multivitamin supplements, but two little-known colorless carotenoids, phytoene and phytofluene, probably also have benefits,” says Nancy Engelmann, a doctoral student in Erdman’s laboratory who helped to develop the new method.

Engelmann optimized the amount of carotenoids in tomato cell cultures by treating already high-achieving tomato varieties with two plant enzyme blockers. The best performers were then chosen for culturing and carbon-13 labeling.

Tomato cells were grown with non-radioactive carbon-13 sugars, yielding carbon molecules that are heavier than the 12-carbon molecules that exist elsewhere.

“These heavy carbon molecules are then incorporated into the carotenoids in the tomato cell cultures. The result is that researchers will be able to track the activity of lycopene, phytoene, and phytofluene and their metabolites,” Erdman says.

Funding from the National Institutes of Health will allow researchers from the University of Illinois and Ohio State University to use the new tool to study carotenoid metabolism in humans. “It’s exciting that we now have the means to pull off this human study,” Erdman says. “It’s work that should move us forward in the fight against prostate cancer.”

More news from University of Illinois: http://www.aces.uiuc.edu/news/

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