In Vitro Antibacterial Activity of Selected Herbal Extracts on Streptococcus mutans

Introduction: Dental caries is an infectious disease associated with numerous microorganisms, mainly Streptococcus mutans. Since consumers mostly have a concern of trustworthy and least harmful products for health care, health industries, including dental care business, have contributed huge effort on production of natural substances. The aim of this study was to investigate the inhibitory effect against S. mutans in vitro of the 95% ethanol extracts from fi ve herbs, Psidium guajava L., Momordica cochinch inensis Spreng.,Glycyrrhiza glabra L., Syzygium aromaticum L. and Piper retrofractum Vahl. Methods: Antimicrobial activity was evaluated using disc diffusion and broth dilution method. The combination inhibitory effects of extracts against S. mutans were also determined using checkerboard assay. Results: Some extracts showed activity against S. mutans. The extract of S. aromaticum showed the largest mean diameter of inhibition zone (16.7±0.5 mm) while the extract of G. glabra was the most effective with the lowest minimum inhibitory concentration (MIC) of 0.195 mg/mL and minimum bactericidal concentration (MBC) of 3.125 mg/mL. A combined extract of S. aromaticum and P. guajava showed a synergistic effect in inhibiting the growth of S. mutans. Conclusion: The results showed that these herbal extracts provide the potential candidate for developing an oral antimicrobial agent to control or prevent dental diseases associated with oral pathogenic bacteria like S. mutans.