Ursolic acid is a triterpenoid compound present in many plants. This study examined the antimicrobial activity of ursolic acid against mutans streptococci (MS) isolated from the Korean population. The antimicrobial activity was evaluated by the minimum inhibitory concentration (MIC) and time kill curves of MS. The cytotoxicity of ursolic acid against KB cells was tested using an MTT assay. The MIC90 values of ursolic acid for Streptococcus mutans and Streptococcus sobrinus isolated from the Korean population were 2 μg/ml and 4 μg/ml, respectively. Ursolic acid had a bactericidal effect on S. mutans ATCC 25175 T and S. sobrinus ATCC 33478 T at > 2 × MIC (4 μg/ml) and 4 × MIC (8 μg/ml), respectively. Ursolic acid had no cytotoxic effect on KB cells at concentrations at which it exerted antimicrobial effects. The results suggest that ursolic acid can be used in the development of oral hygiene products for the prevention of dental caries.

• Joong-Ki Kook(Department of Oral Biochemistry and Oral Biology Research Institute, School of Dentistry) Corresponding author
• Min Jung Kim(Department of Oral Biochemistry and Oral Biology Research Institute, School of Dentistry) Contributed equally
• Chun Sung Kim(Department of Oral Biochemistry and Oral Biology Research Institute, School of Dentistry) Contributed equally
• Jae-Yoon Park(Department of Biochemistry and Molecular Biology, Medical School, Chosun University) Contributed equally
• Yun Kyong Lim(Department of Oral Biochemistry and Oral Biology Research Institute, School of Dentistry)
• Soon-Nang Park(Department of Oral Biochemistry and Oral Biology Research Institute, School of Dentistry)
• Sug-Joon Ahn(Dental Research Institute and Department of Orthodontics, College of Dentistry, Seoul National University)
• Dong-Chun Jin(Department of Veterinary Medicine, College of Agriculture, Yanbian University)
• Tae Hyung Kim(Department of Restorative Sciences, Herman Ostrow School of Dentistry, University of Southern California)