Objective To determine the effects of licorice decoction on the adherence of Streptococcus mutans in vitro and the possible mechanisms. Methods Licorice decoction was from self-preparation. According to the licorice decoction’s mass concentration 25, 50 and 100 g•L-1, the experiment were divided into A, B and C groups. The group not containing decoction was set as negative control group. The experiment was performed in the glass tubes. Bacteria adhering tightly, loosely or not adhering to the glass were collected separately to determine bacteria’s adhesion rates. The quantity of water insoluble extracellular polysaccharides produced by bacteria was measured by anthrone method. Results Bacteria’s adhesion rates of A, B, C and negative control groups were 70.2%, 40.1%, 14.2% and 87.1% respectively. Water insoluble extracellular polysaccharides’s mass concentration of each group was 0.28, 0.25, 0.13, 0.30 g•L-1. Conclusion Licorice decoction has inhibitory potential against the adherence of Streptococcus mutans to smooth surface. The inhibition was dose-dependent, and may be relevant with the inhibition of synthesis of water insoluble extracellular polysaccharides.
