The Antimicrobial Effects of Licorice Extract against Streptococcus mutans as a Potential Oral Gel against Dental Caries

Introduction: Dental caries is a prevalent chronic infectious disease primarily associated with Streptococcus mutans. Natural compounds with antimicrobial properties, such as licorice (Glycyrrhiza glabra), offer promising alternatives for oral health care. Methods: Licorice roots were authenticated by a botanist and processed into an extract. The extract was formulated into an oral gel (100 μg/mL) and sterilized using gamma irradiation. The minimum inhibitory concentration (MIC) of the gel against S. mutans was determined by the agar dilution method. Sub-MIC concentrations were used in a time-kill assay to assess antibacterial efficacy. A reduction of ≥3 log10 CFU/mL was considered indicative of antibacterial activity. Data were ana-lyzed using the Shapiro-Wilk test, Kruskal-Wallis, and Tukey’s post hoc test (SPSS v25, p < 0.05). Results: The MIC of the gel was found to be 1260 μg/mL. Time-kill assays using concentrations of 1.4 and 1.8 μg/mL showed a significant reduction in bacterial count over time, demonstrating effec-tive antibacterial action against S. mutans. Discussion: The results suggest that even sub-MIC levels of licorice gel can significantly inhibit S. mutans, highlighting its potential for incorporation into preventive or therapeutic oral health products. Conclusion: Licorice extract gel exhibits promising antimicrobial activity against S. mutans and may be considered a potential natural agent in oral formulations targeting dental caries.