| Summary: | 碩士 === 國立陽明大學 === 生化暨分子生物研究所 === 97 === Dental plaque is a complex biofilm that accumulates on the hard tissues (teeth) in the oral cavity and leads to dental caries. Streptococcus mutans is regarded as the principal etiologic agent of human dental caries. There are many major virulence properties of S. mutans associated with caries formation process include adhesion, biofilm formation, acidogenicity, and acid tolerance.
Dozens of essential oils (E.O.s) were screened. Several candidates of E.O.s such of spikenard, sandalwood and sedarwood E.O.s had effects on reducing attached S. mutans biomass in in vitro microtiter-plate screening test. Spikenard E.O. was chosen to be a target material to test inhibition of virulence of S.mutans. The spikenard E.O. was fractionated by silica column chromatography and fractions were tested the effect of reduction attached biomass. Fraction 2 was the most effective portion of all fractions. Spikenard E.O. and Fraction 2 later were be tested the activity of inhibition of S. mutans’s virulence properties. The major compounds of spikenard E.O. and Fraction 2 are sesquiterpene determined by using gas chromatography-mass spectrometry..
Minimum inhibitory concentration (MIC) of spikenard E.O. and Fraction 2 were 139�慊/ml and 273.4�慊/ml respectively. Spikenard E.O. and Fraction 2 could substantially reduce attached biomass, total viability and WIG content in a dose-dependent manner under sub-MIC.
The glucosyltransferase and fructosyltrasferase enzymes of S. mutans catalyze the formation of extracellular polymers. RT-PCR analysis for the expression of these genes showed expression of gtf-B and gtf-C genes can be inhibited under high sub-MIC of spikenard E.O. and Fraction 2. However ftf gene expression was attenuated only by Fraction 2 under high sub-MIC. The significant attenuation of S. mutans’s biofilm formation by spikenard E.O. demonstrated that spikenard E.O. would be a potent natural product for the prevention of dental caries.
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