In vitro anticariogenic effect of gallic acid against Streptococcus mutans

Involvement of Streptococcus mutans in the pathogenesis of dental caries among human populations is well established. Here, we studied the effect of gallic acid, a naturally occurring polyphenol on certain cariogenic activities of S. mutans. Gallic acid inhibited the glycosyltransferase activity, a key enzyme of sucrose metabolism by 27-36% in S. mutans. Minimal inhibitory concentration (MIC) of gallic acid (136 mu g/mL) inhibited the growth of S. mutans by 50%. About 0.4 mM of the polyphenol reduced biofilm formation by 40%, hydrophobicity 60% and acid production 36% by the organism under in vitro growth conditions. Fluorescence microscopy revealed that in absence of gallic acid, the cells were present as clumps, however in the presence of gallic acid (68 mu g/mL), they were well segregated due to the inhibition of biofilm formation. The present findings suggest that gallic acid has cariostatic activity against S. mutans, which may have potential application in prevention of dental caries.