Effect of Magnolia Bark Extract and Flavor Oils on Nitrate Reductase of Oral Bacteria

Objectives: Dietary nitrate from foods can be metabolized to nitrite by nitrate reductase produced by anaerobic oral bacteria. Human gut bacteria convert nitrite to nitric oxide, which has been linked to cardiovascular health. Antimicrobial magnolia bark extract (MBE) and plant essential oils have been incorporated into chewing gum and mints for breath freshening benefit. We hypothesize that these agents do not suppress in vitro nitrate reductase activity of selected oral anaerobes and human salivary bacteria. Objective: This study investigated the effect of chlorhexidine, MBE, peppermint and spearmint oils on nitrate reductase activity of salivary bacteria and selected halitosis-associated oral anaerobes.
Methods: Adult stimulated whole saliva was collected over a 5-minute period while chewing a 1g piece of unflavored unsweetened gum. Human salivary bacteria and selected anaerobic oral bacteria commonly associated with human oral malodor were examined for their ability to generate nitrite from nitrate source. The nitrate reductase activity was assayed using the Griess reagent. Nitrate reductase activity in the presence of chlorhexidine, MBE, peppermint and spearmint oils were examined.
Results: Salivary bacteria, Aggregatibacter actinomycetemcomitans, Actinomyces naeslundii and Veillonella atypica were the major nitrate reductase producers. Porphyromonas gingivalis, Fusobacterium nucleatum, Enterococcus faecalis and selected streptococcal species did not contribute significantly to salivary nitrite generation. Treatment of A. actinomycetemcomitans, A. naeslundii and V. atypica with natural germ-kill MBE (100 µg/ml, 10 min) or spearmint and peppermint flavor oils (0.1%) did not significantly affect nitrate reductase activity while chlorhexidine at 0.01% showed inhibition.
Conclusions: When incorporated into chewing gum and mints, flavor oils and magnolia bark extract do not significantly affect nitrate reductase activity of oral bacteria. The use of these products is unlikely to have undesirable impact on blood pressure and systemic health in humans (Research supported by Mars Wrigley, Chicago IL; and Pediatric Dentistry Department, College of Dentistry, University of Illinois-Chicago).