Effects of the Ethanolic Extracts of Guava Leaves, Licorice Roots and Cloves on the Cariogenic Properties of Streptococcus mutans

Introduction: Streptococcus mutans is a major causative pathogen of dental caries. This study aimed to investigate the effects of the ethanolic extracts of Psidium guajava, Glycyrrhiza glabra and Syzygium aromaticum against cariogenic properties of Streptococcus mutans. These medicinal plants have been used traditionally as the ingredients in the herbal mouthwash for the management of dental caries. Methods: The 95% ethanolic extracts of these medicinal plants were prepared and their phytochemical contents were analyzed by using thin layer chromatography-densitometry. Antibacterial activities of the extracts against S. mutans were evaluated according to broth dilution method. The effects of the extracts against cariogenic properties of S. mutans, which are surface adherence, biofilm formation and acid production, were also investigated. Results: The biological active constituents, quercetin, glycyrrhizic acid and eugenol, were found in P. guajava, G. glabra and S. aromaticum, respectively. The three extracts possessed anti-bacterial activity against S. mutans with the MICs of 1.562, 0.195 and 1.562 mg/mL, respectively. The extracts at every concentration tested (at lower than their MICs) significantly inhibited cariogenic properties of S. mutans, which included inhibitions against surface adherence, biofilm formation and acid production. Conclusion: The ethanolic extracts of guava leaves, licorice roots and cloves produced anti-bacterial and anti-cariogenic activities against S. mutans. These plant extracts thus can potentially be developed as a product for the prevention of dental caries in the near future.