Abstract
Organic compounds from plants are an attractive alternative to conventional antimicrobial agents. Therefore, two compounds namely M-1 and M-2 were purified from
Origanum vulgare
L. and were identified as carvacrol and thymol, respectively. Antimicrobial and antibiofilm activities of these compounds along with chlorhexidine digluconate using various assays was determined against dental caries causing bacteria
Streptococcus mutans
. The IC
50
values of carvacrol (M-1) and thymol (M-2) against
S
.
mutans
were 65 and 54 µg/ml, respectively. Live and dead staining and the MTT assays reveal that a concentration of 100 µg/ml of these compounds reduced the viability and the metabolic activity of
S
.
mutans
by more than 50%. Biofilm formation on the surface of polystyrene plates was significantly reduced by M-1 and M-2 at 100 µg/ml as observed under scanning electron microscope and by colorimetric assay. These results were in agreement with RT-PCR studies. Wherein exposure to 25 µg/ml of M-1 and M-2 showed a 2.2 and 2.4-fold increase in Autolysin gene (
Atl
E) expression level, respectively. While an increase of 1.3 and 1.4 fold was observed in the super oxide dismutase gene (
sod
A) activity with the same concentrations of M-1 and M-2, respectively. An increase in the
ymc
A gene and a decrease in the
gtf
B gene expression levels was observed following the treatment with M-1 and M-2. These results strongly suggest that carvacrol and thymol isolated from
O. vulgare
L. exhibit good bactericidal and antibiofilm activity against
S
.
mutans
and can be used as a green alternative to control dental caries.