Oleanolic acid is a natural triterpenoid that exists widely in foods and some medicinal herbs. The purpose of this study was to determine the antimicrobial activity of oleanolic acid against Streptococcus mutans strains isolated from a Korean population. Antimicrobial activity against these bacteria was evaluated by minimal inhibitory concentration (MIC) and time kill curves. The tolerance of human gingival fibroblasts and human periodontal ligaments to oleanolic acid was tested using a methyl thiazolyl tetrazolium (MTT) assay. The MIC90 value of oleanolic acid for both S. mutans and S. sobrinus isolated from Koreans was 8μg/mℓ. Oleanolic acid showed bactericidal effects against S. mutans ATCC 25175T and S. sobrinus ATCC 33478T at 1 × MIC(8μg/mℓ) and had no cytotoxic effects against KB cells at this dose. The results suggest that oleanolic acid could be useful in the future development of oral hygiene products for the prevention of dental caries.

• Min Jung Kim(Department of Oral Biochemistry, Oral Biology Research Institute, School of Dentistry, Chosun University) Contributed equally
• Chun Sung Kim(Department of Oral Biochemistry, Oral Biology Research Institute, School of Dentistry, Chosun University) Contributed equally
• Woo-Hyung Ha(Department of Dental Materials)
• Byung-Hoon Kim(Department of Dental Materials)
• Yun Kyong Lim(Department of Oral Biochemistry)
• Soon-Nang Park(Department of Oral Biochemistry, Oral Biology Research Institute, School of Dentistry, Chosun University)
• Yu Jin Cho(Department of Oral Biochemistry)
• Myungmi Kim(Department of Oral Biochemistry)
• Jang-Hyuk Ko(Department of Dental Materials)
• Soon-Sung Kwon(Department of Dental Materials)
• Yeong-Mu Ko(Department of Dental Materials, Oral Biology Research Institute, School of Dentistry, Chosun University)
• Joong-Ki Kook(Department of Oral Biochemistry, Oral Biology Research Institute, School of Dentistry, Chosun University) Corresponding author