Bioactivity-guided separation of anti-acidogenic substances against Streptococcus mutans UA 159 from Polygonum cuspidatum

Objectives: The aim of this study was to separate the anti-acidogenic substances against Streptococcus mutans UA 159 from Polygonum cuspidatum. Material and methods: The anti-acidogenic substances were separated by a series of liquid-liquid fractionations followed by normal-phase silica gel liquid chromatography, based on high-performance liquid chromatography and glycolytic pH-drop assay. The effectiveness of the separated substances on the acidogenicity of Streptococcus mutans UA 159 was examined using sodium fluoride as a positive control. The chemical composition and quantities of the components of the substances was also assessed by qualitative-quantitative chromatographic analysis. Results: Among the substances separated from P. cuspidatum, F3 showed the strongest inhibitory effect on the acidogenicity of S. mutans UA 159 in a dose-dependent manner without displaying any bactericidal activity. F3 decreased the acidogenicity of S. mutans even at 12.5 μg ml^-1 (P < 0.05). F3 consisted mainly of resveratrol and emodin (C₁₄H ₁₂O₃ and C₁₄H₄O₂(OH) ₃CH₃, respectively), which made up approximately 60% of the weight of F3. Conclusion: F3 can be considered as a promising agent for controlling the acidogenicity of S. mutans and subsequent dental caries formation.