Anticariogenic Potential of Korean Native Plant Extracts against Streptococcus mutans

Numerous chemically synthesized compounds are widely used in oral hygiene products. However, due to their potential risk, there is a need to improve the safety and quality of dental care by seeking alternative control agents such as those naturally found in plant materials. Here we assessed antibacterial potentials of extracts from 100 species of Korean native plants against Streptococcus mutans on cariogenesis. Among those, extracts from five plants (Arctii Fructus, Caryopteris incana, Aralia continentalis, Symplocarpus renifolius, and Lamium amplexicaule) showed a growth inhibition of S. mutans. The five extracts were further individually evaluated for their minimal inhibitory concentration and minimal bactericidal concentration. Interestingly, a synergistic antibacterial activity was observed with the combination of sodium fluoride and the plant extracts. To determine the anti-biofilm activity of plant extracts, S. mutans was treated with increasing concentrations of the extracts in the range from 1250 to 3750 µg/mL. When S. mutans was grown in the defined biofilm medium containing the individual extracts of 47 species, the biofilm amount markedly decreased compared to that of a negative control. Notably, the extract of S. renifolius significantly downregulated the gtf and spaP genes for synthesis of glucan and adhesive proteins in S. mutans, and L. amplexicaule decreased the expression of gtfD gene. Therefore, these results demonstrate that the five plant extracts modulate survival and pathogenesis of S. mutans by growth inhibition and downregulation of the gene(s) implicated in biofilm formation.