A team from the University of California Los Angeles and Oceanspray Cranberry has previously demonstrated that a cranberry extract prevented adhesion of the bacteria Streptococcus mutans, an agent for dental caries, to teeth.
The new research, presented last week at the 84th General Session of the International Association for Dental Research, goes some way to identifying the compounds in cranberries that could be responsible and the mechanisms behind these benefits.
Tooth decay is said to be the most common oral infectious disease that afflicts humans, with over 95 per cent of all adults having experienced it. The American public is reported to spend almost $40bn (€31bn) every year to treat decay or its consequences.
Tooth decay results from the interaction of specific bacteria with constituents of the diet on a susceptible tooth surface. Dental plaque accumulation is the first clinical evidence of this interaction; dental plaque is a biofilm that is comprised of a population of bacteria growing on the tooth surface enmeshed in a polysaccharide matrix. Acid can be formed rapidly by acidogenic bacteria, such as S. mutans, and its persistence results in dissolution of the tooth.
Scientists from the University of Rochester School of Medicine and Dentistry in New York reported that flavonoids in cranberries might be able to reduce the formation of plaque, inhibit acidic conditions, and stop the bacteria from sticking to teeth.
Previous research from the same scientists led the British Dental Health Foundation, which offers impartial dental advice to the public, to advise people to drink cranberry juice (in moderation and at meal-times) to boost oral health.
Lead researcher Hyun Koo and his colleagues investigated the effects of the flavonoids quercetin and myricetin, and their corresponding glycosides on the inhibition of glucosyltransferase enzymes (GTF) associated with plaque formation. Tests were performed in solution and on saliva-coated hydroxyapatite (calcium compounds sometimes used in dental implants).
They found that solutions containing 250 micrograms per millilitre of the flavonoids quercetin and myricetin inhibited the activity of glucosyltransferase enzymes by about 55 per cent in solution and by as much as 40 per cent on the hydroxyapatite.
Expression of the gene responsible for producing the glucosyltransferase enzymes was said to be repressed.
The flavonoids also inhibited the drop in pH (acid conditions) when the bacteria were kept in solution.
"Our data show that quercetin and myricetin are active compounds in cranberry that modulate the virulence factors involved in S.mutans acidogenicity and biofilm formation," concluded the researchers.
The popularity of cranberries has been increasing in recent years as a combination of strong marketing campaigns and a body of scientific evidence revealing the fruit's health benefits have contributed to growing consumer awareness and interest in the product.
The fruit has long been considered an effective method of fighting urinary tract infections, something that has led to almost one third of parents in the US giving it to their children, according to a recent study.
In 2004 France became the first country to approve a health claim for the North American cranberry species vaccinium macrocarpon, which states that it can 'help reduce the adhesion of certain E.coli bacteria to the urinary tract walls'.