Effect of Manuka Honey and Licorice Root Extract on the Growth of Porphyromonas gingivalis: An In Vitro Study

Chronic bad breath (also known as “halitosis”) is very common in general population and nearly 50% of the general population have halitosis. Liquid mouthwashes such as Listerine®, and ACT®, mouth fresheners, and sugar-free gum are commonly used to alleviate bad breath, but these products are not portable, have many side effects, or only temporarily mask the problem. Hence, a lozenge made from natural ingredients would be an excellent alternative to reduce bad breath. We evaluated the effectiveness of natural ingredients such as Manuka Honey and Licorice root extract in reducing growth of Porphyromonas gingivalis, one of the main bacteria that cause bad breath. Solutions containing Manuka honey and/or licorice root extract, Listerine®, or ACT® were added to P. gingivalis cultures to assess their effect on bacterial growth. After 18 hours, the absorbance at 680nm of each solution was measured as an indicator of growth. We found that Manuka honey is almost as effective as Listerine® and ACT® in reducing P. gingivalis growth, while licorice root extract, had a very minor effect. Aliquots from the cultures that were inoculated on to brain heart infusion (BHI) plates showed similar trends on growth inhibition. These data suggest that a natural lozenge made from Manuka honey may be effective in reducing bad breath.