Effect of a water-soluble extracts of propolis on Streptococcus mutans

Objectives: The water-soluble extracts of propolis(WSEP) has practical advantages in contrast to the ethanolic extracts. Since components of propolis might be different depending on different methods of extraction.The aim of this study was to evaluate the effect of a WSEP (supplied by Bee Research Institute, Chinese Academy of Agricultural) on cariogenic factors of Streptococcus mutans. Methods: Sterilized stainless-steel cylinders and agar diffusion methods as well as TEM were used to determine the activity of WSEP against Streptococcus mutans Ingbritt C (S.mutans) respectively. Minimum inhibitory concentrations (MIC) and minimum bactericidal concentrations (MBC) were assessed. Three ladders of WSEP concentrations ranging between MBC and MIC were chosen to analyze inhibitory effects on water-insoluble glucan(WIG) synthesis , acid producing and adsorbed onto saliva-coated hydroxyapatite of S.mutans, respectively. Results: The MIC was 0.3125 mg/ml WSEP, and MBC was 10.00 mg/ml WSEP. TEM showed that WSEP inhibited S. mutans growth by preventing cell division, disrupting the organization of cytoplasm, cytoplasmic membrane, and cell wall. Compared with the negative control, WIG synthesis was markedly inhibited by WSEP at 5.00mg/ml, 1.25mg/ml (p<0.01), and 0.3125mg/ml(p<0.05). WSEP inhibited activity of acid-producing of S. mutans at 5.00 mg/ml and 1.25 mg/ml. The amount of lactic acid in supernatants was significantly less and the pH value was higher in two experimental groups than the control group (p<0.01). There was no significant difference between 0.3125 mg/ml group and the control. Meanwhile, 5.00 mg/ml and 1.25 mg/ml WSEP showed strong inhibitions of adsorption of S.mutans. The percent of inhibition were 57.32% and 54.97%. Conclusion: The results suggest that WSEP may have ability on caries prevention by antibacterial activity, inhibition of bacteria adherence and inhibition of water-insoluble glucan and acid formation. The effective components of WSEP and the optimal concentration against S.mutans need further study to determine.