Survival of berries’ anthocyanins in the mouth

February 4, 2013

A study published in Food Chemistry shows that certain anthocyanins found in berries may be susceptible to degradation in the mouth, and therefore not provide their full health benefits. Anthocyanins are compounds that give colorful fruits their rich hues, especially berries, as well as promote health and perhaps even prevent cancer. But for the first time, scientists have exposed extracts from numerous berries high in those pigments to human saliva to see just what kinds of health-promoting substances are likely to survive and be produced in the mouth.

The researchers asked 14 healthy individuals, ages 21–55, to collect saliva in the morning before they had eaten breakfast or brushed their teeth. Research participants later collected additional saliva samples before and after they had rinsed their mouths with an antibacterial liquid. The five fruits selected for study— blueberries, chokeberries, black raspberries, red grapes, and strawberries—allowed the scientists to test the six distinct families of the anthocyanin pigments.

Researchers purified the anthocyanins from each berry type and added the extracts to saliva. The extent of the pigment degradation in saliva was primarily a function of the chemical structure of a given anthocyanin. Two families of anthocyanins consistently degraded when exposed to saliva: delphinidin and petunidin. Four other families were more stable: cyanidin, pelargonidin, peonidin, and malvidin.

“Our observations suggest that the bacteria within one’s oral cavity are a primary mediator of pigment metabolism. The bacteria are converting compounds that are present in the foods into metabolites,” said Mark Failla, Professor of Human Nutrition at Ohio State and Interim Chair of the Dept. of Human Sciences. “One area of great interest is whether the health-promoting benefits associated with eating anthocyanin-rich fruits like berries are provided by the pigment itself, the natural combinations of the pigments in the fruit, or the metabolites produced by bacteria in the mouth and other regions of the gastrointestinal tract.”

To complicate the situation, multiple studies have led to the conclusion that anthocyanins themselves are very poorly absorbed by the body. So, if anthocyanins are the actual health-promoting compound, you would want to design food products, confectionaries, and gels containing mixtures of anthocyanins that are stable in the mouth. If, on the other hand, the metabolites produced by the metabolism of anthocyanins are the actual health-promoting compounds, there will be greater interest in fruits that contain anthocyanins that are less stable in the oral cavity.

This research group is continuing the work, examining which bacteria are most involved in the metabolism of anthocyanins, and testing the stability of the pigments in berry juices in the mouths of human volunteers rather than in test tubes containing their saliva.