Streptococcus mutans and Streptococcus sobrinus play important roles in dental caries. Coptis chinensis is a natural product with antimicrobial activity against enterobacteria; however, its effects on oral streptococci are still unknown. Therefore, the effects of C. chinensis on the growth and biofilm formation of the representative cariogenic bacteria S. mutans and S. sobrinus were investigated for the possible use of C. chinensis as an anticaries agent. The C. chinensis extract was diluted with sterile distilled water, and 0.1–2.5% of the extract was used in the experiment. The effects of the C. chinensis extract on the growth and glucan formation of S. mutans and S. sobrinus were measured by viable cell counting and spectrophotometry at 650 nm absorbance, respectively. Crystal violet staining was also carried out to confirm the C. chinensis extract’s inhibitory effect on biofilm formation. The C. chinensis extract significantly inhibited the growth of S. mutans and S. sobrinus at concentrations of ≥ 0.3% as compared with the control group. The viable cell count of colonies decreased by 1.7-fold and 1.2-fold at 2.5% and 1.25%, respectively, compared with the control group. The biofilm formation of S. mutans and S. sobrinus was inhibited by > 20-fold at C. chinensis extract concentrations of ≥ 1.25% as compared with the control group. In summary, the C. chinensis extract inhibited the growth and biofilm and glucan formation of S. mutans and S. sobrinus . Therefore, C. chinensis might be a potential candidate for controlling dental caries.

Introduction
Materials and Methods
    1. Bacterial culture
    2. Preparation and treatment of CC extract and othernatural extracts
    3. Screening experiments of herbal extracts against S.mutans and S. sobrinus
    4. Measurement of growth of S. mutans and S. sobrinus
    5. Viable cell count
    6. Measurement of biofilm formation
    7. Glucan synthesis test
Results
    1. Screening of natural extract with antibacterialactivity
    2. Effect of CC extract on the growth of S. mutansand S. sobrinus
    3. Effect of CC extract on biofilm formation
    4. Effect of CC extract on glucan synthesis
Discussion
Acknowledgements
Conflicts of Interest
References

• Si Yeong Kim(Department of Oral Microbiology, School of Dentistry, Pusan National University)
• Yuri Song(Department of Oral Microbiology, School of Dentistry, Pusan National University)
• Hyun Ah Lee(Department of Oral Microbiology, School of Dentistry, Pusan National University)
• Hee Sam Na(Department of Oral Microbiology, School of Dentistry, Pusan National University)
• Chul Jong Jung(Department of Okchundang Research Institute)
• Gyung Yun Bek(Department of Okchundang Research Institute)
• and Jin Chung(Department of Oral Microbiology, School of Dentistry, Pusan National University) Correspondence to