Evaluation of the antimicrobial properties of licorice extract oral gel on streptococcus mutans

Abstract

Background: Documenting and investigating the effectiveness of medicinal plants using the scientific method is very important. In recent years, the use of plant extracts in modern medicine has increased. Licorice plant is one of these medicinal plants that is widely used in the field of dentistry and oral diseases. Materials and methods: The licorice plant was identified by a botanist for their authenticity. After the steps of separating the extract from it, licorice extract was prepared in the form of oral gel. The prepared gel (100 µg/mL) was sterilized by gamma rays. In order to evaluate the effectiveness of the prepared antimicrobial gel, first the lowest bacterial growth inhibitor concentration (MIC) of the gel was determined by agardilution method. Then subMIC concentrations were used to perform the time-kill assay method. A decrease of at least three times the value of Log10 in CFU/mL of bacteria was considered as the antibacterial effect of the studied concentration. Mann-Whitney test was used for statistical analysis between control and intervention groups. SPSS version 25 software was used for data analysis. A value less than 0.05 was considered significant. Results: The MIC value for the desired gel was 1260 μg/mL. According to the results, concentration equal to 1/4 and 1/8 MIC of the prepared gel was obtained in one time. Therefore, gel concentrations of 1.4 and 1.8 were used to perform the time-kill test. The results showed that over time, the gel prepared for both selected concentrations had appropriate killing effects against Streptococcus mutans bacteria. Conclusion: Due to the appropriate antimicrobial property of licorice extract gel on Streptococcus mutans bacteria, various oral formulations can be prepared from this material for the prevention or treatment of oral and dental diseases.