Abstract
Pharmacological studies have linked a number of human health benefits with licorice due to its anticancer, anti-inflammatory, anti-oxidant, and antimicrobial properties. The aim of this study was to investigate the effects of licoricidin and glabridin, two major licorice isoflavans, on growth and virulence properties (biofilm formation, acid production, dextran production, adherence) of the cariogenic bacterium Streptococcus mutans. Moreover, the biocompatibility of these licorice compounds was assessed in an in vitro model of oral keratinocytes. We used a broth microdilution assay to show that licoricidin and glabridin exhibit a marked antibacterial activity against S. mutans. Glabridin and, to a lesser extent, licoricidin reduced the biofilm viability of S. mutans. In addition, glabridin decreased the production of dextran by S. mutans. The two licorice isoflavans attenuated the adherence of S. mutans to a saliva-coated hydroxylapatite surface, and reduced acid production from glucose. Lastly, depending on the concentrations tested, the two licorice isoflavans showed no or low toxicity toward oral keratinocytes. Within the limitations of this study, our data suggest that licoricidin and glabridin may be promising agents for controlling dental caries.
Highlights
Dental caries is a chronic infectious disease associated with the progressive destruction of the hard tooth structures resulting from the metabolism of acidogenic/aciduric bacteria embedded in dental biofilms
Mouthwashes supplemented with chemoprophylactic agents that inhibit the growth, adhesion, and biofilm formation of cariogenic bacteria can be used as adjuncts to good oral hygiene practices [4,5]
The antibacterial activities of the two licorice compounds were investigated by determining their minimal inhibitory concentrations (MICs) and minimal bactericidal concentrations (MBCs) against one reference (ATCC 25175) and four clinical (12A, 33A, INB, T8) strains of S. mutans in a broth microdilution assay (Table 1)
Summary
Dental caries is a chronic infectious disease associated with the progressive destruction of the hard tooth structures (enamel, dentin, and cementum) resulting from the metabolism of acidogenic/aciduric bacteria embedded in dental biofilms. This disease affects over 35% of people of every age group worldwide, in developing countries [1]. Efficient removal of dental plaque is not always possible, especially by handicapped or elderly individuals who lack the necessary dexterity or motivation To overcome these shortcomings, mouthwashes supplemented with chemoprophylactic agents that inhibit the growth, adhesion, and biofilm formation of cariogenic bacteria can be used as adjuncts to good oral hygiene practices [4,5]. As a number of undesirable effects, including tooth staining, unpleasant taste, and the emergence of bacterial resistance, have been associated with the chemoprophylactic agents added to mouthwashes [6,7], there is a need to identify alternatives
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