• Kitti Torrungruang D.D.S., M.S.D (Periodontics), Ph.D.
• Piraporn Vichienroj D.D.S., M.S.
• Suchada Chutimaworapan B. Pharm., Ph.D.

Objective The purpose of this study was to examine the antibacterial activity of extract from
mangosteen pericarp against Streptococcus mutans, bacteria associated with dental plaque formation
and caries development.

Materials and methods Bacterial strains used in this study were S. mutans ATCC 25175 and
KPSK2. Antibacterial activity was expressed as minimum inhibitory concentration (MIC) and
minimum bactericidal concentration (MBC). The rates at which bacteria were killed were also
determined by exposure to the extract at 2x and 4x MBC for varying time periods.

Results The extract was effective against both strains of S. mutans. The MIC and MBC for the
strain ATCC 25175 were both equal to 0.625 μg/ml. The respective values for the strain KPSK2
were 0.625 and 1.25 μg/ml. The MIC and MBC were comparable to those of chlorhexidine,
an antiseptic commonly used in dental plaque control. Time-kill assays for the strain ATCC
25175 showed that treatment with the extract at 2x MBC caused a significant decrease in viable
count (log₁₀ colony forming units/ml) of almost one order of magnitude after 90 minutes. When the
extract concentration was increased to 4x MBC, the viable bacterial count was reduced by almost
two orders of magnitude in 60 minutes, and was further decreased to an undetectable level in
90 minutes.

Conclusion Mangosteen pericarp extract possessed strong antibacterial activity against S. mutans.
These results suggest that the extract may be developed as a new agent for dental plaque control
and caries prevention.

(CU Dent J. 2007;30:1-10)