ABSTRACT
OBJECTIVES: In this study, the destabilizing effect of glycyrrhetinic acid on pre-formed biofilms of Streptococcus mutans (S. mutans) was observed. METHODS: Alamar blue assay was used to determine the toxicity of glycyrrhetinic acid on pre-formed biofilms of S. mutans. Four different concentrations (0, 3.75, 7.5, 15 µg/ml) of glycyrrhetinic acid were tested. Changes in the biofilm architecture after exposure to glycyrrhetinic acid were analyzed by scanning electron microscopy (SEM). Moreover, the role of glycyrrhetinic acid in enhancing the antimicrobial activity of cetylpyridinium chloride (CPC), an antimicrobial agent commonly used in oral health care products, was evaluated. RESULTS: Glycyrrhetinic acid concentration of up to 15 µg/ml had little cytotoxic effect but significantly changed the biofilm architecture. SEM analysis revealed destabilized biofilm structure after the preformed biofilms were exposed to glycyrrhetinic acid. Supplementing 2.5 µg/ml CPC with 15 µg/ml glycyrrhetinic acid significantly enhanced the bactericidal effect of CPC on the pre-formed biofilms than that in the non-supplemented CPC treated control. This indicates that glycyrrhetinic acid enhanced the antimicrobial activity of CPC by modifying the structure, thus facilitating the penetration of CPC into the biofilm. CONCLUSIONS: Glycyrrhetinic acid could be a potential agent to effectively control S. mutans biofilms responsible for dental caries.