Study of some medicinal plants effective against microorganisms found in oral cavity

In this study, three different kinds of Thai Medicinal Plants have been selected to study antibacterial activity against Staphylococcus aureus, Streptococcus mutans and Streptococcus sanguis which are the main causes of dental caries. The plants studied are: 1. Cymbopogon nardus Rendle (Fam. Graminae), which in Thai is called "Tra Kri Horm" 2. Caesalpinia sappan, Linn, (Fam. Caesalpiniaceae), or "Fang" in Thai. 3. Psidium guajava (Fam. Myrtaceae) or "Farang" as a Thai name. The antibacterial activity of these plants is compared to that of antibiotic, Penicillin G and antiseptic, Chlorhexidine. The Minimum Inhibitory Concentration (MIC) of these plants extracts on these microorganisms was determined by the agar dilution method. It was found that the MIC of the aqueous extract from Caesalpinia sappan on Strep. mutans and Staph. aureus was 16-32 mg/ml, and on Strep. sanguis was more than 64 mg/ml. The MIC of the alcoholic extract of Caesalpinia sappan on Staph. aureus and Strep. mutans was 298 mg/ml. The alcoholic extract of Caesalpinia sappan on Staph. aureus and Strep. mutans was 298 mg/ml. The alcoholic extract of Psidium guajava was found to have the MIC of 125 mg/ml on Strep. sanguis and 250 mg/ml on Strep. mutans. The volatile oil from Cymbopogon nardus also inhibited growth of these three microorganisms. The MIC was less than 0.2 %. The MIC of Penicillin G on Staph. aureus was 0.12-0.5 ug/ml and 0.063 ug/ml on both Strep. mutans, and Strep sanguis. The MIC of Chlorhexidine was less than 0.002 %. From this study these three medicinal plants have shown antibacterial activity on Strep. mutans, Strep. sanguis and Staph. aureus by having different MIC. The plants having the potential of this activity are Caesalpenia sappan and Cymbopogon nardus. From this study, it has been shown that it is valuable to develop new drugs from these plants. Further investigation should be carried out.