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,” Failla said. “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.”

There is context for this study that further complicates the understanding of anthocyanins’ benefits. Multiple studies have led to the conclusion that anthocyanins themselves are very poorly absorbed by the body.

“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,” Failla said. “We lack such insights at this time.”

The extent to which the anthocyanins were degraded varied among the 14 people whose saliva was used in the study. However, two families of anthocyanins consistently degraded the most in all volunteers. Failla said the observed variation among individuals is likely related to differences in the microbial community that resides in each person’s mouth.

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.

This work was supported in part by OARDC, the research arm of Ohio State's College of Food, Agricultural, and Environmental Sciences.

Co-authors include Kom Kamonpatana of the Interdisciplinary Ph.D. Program in Nutrition; Monica Giusti and Ken Riedl of the Department of Food Science and Technology; Chureeporn Chitchumroonchokchai of the Department of Human Nutrition; and Maria MorenoCruz and Purnima Kumar of the Department of Periodontology, all at Ohio State. All but MorenoCruz are also investigators in the Food Innovation Center.