Raisins fight oral bacteria

13/06/05 "Our laboratory analyses showed that phytochemicals in this popular snack food suppressed the growth of oral bacteria associated with caries and gum disease," said Christine Wu, professor and associate dean for research at the UIC College of Dentistry and lead author of the study. Phytochemicals are compounds found in higher plants.

The data were presented today at the annual meeting of the American Society for Microbiology in Atlanta.

Wu and her co-workers performed routine chemical analyses to identify five phytochemicals in Thompson seedless raisins: oleanolic acid, oleanolic aldehyde, betulin, betulinic acid and 5-( hydroxymethyl )-2-furfural.

Oleanolic acid, oleanolic aldehyde, and 5-( hydroxymethyl )-2-furfural inhibited the growth of two species of oral bacteria: Streptococcus mutans, which causes cavities, and Porphyromonas gingivalis, which causes periodontal disease. The compounds were effective against the bacteria at concentrations ranging from about 200 to 1,000 micrograms per milliliter.

Betulin and betulinic acid were less effective, requiring much higher concentrations for similar antimicrobial activity.

At a concentration of 31 micrograms per milliliter, oleanolic acid also blocked S. mutans adherence to surfaces. Adherence is crucial for the bacteria to form dental plaque, the sticky biofilm that accumulates on teeth. After a sugary meal, these bacteria release acids that erode the tooth enamel.

Wu said that the findings counter a longstanding public perception that raisins promote cavities.