Inhibitory activity of Dodonaea viscosa var. angustifolia extract against Streptococcus mutans and its biofilm.

BACKGROUND

The leaves of Dodonaea viscosa var. angustifolia (DVA) are traditionally used for the treatment of fever, colds, oral thrush, toothaches and related problems. Streptococcus mutans is implicated in many oral infections. This study investigated the inhibitory activity of DVA extract against Streptococcus mutans and its biofilm.

METHODS

Crude extract of the leaves was prepared using methanol. The time-kill curve for Streptococcus mutans at different concentrations of methanol extract after 6 and 24 h was determined. Biofilms of Streptococcus mutans were grown in the presence of subinhibitory concentration of extract (0.78 mg/ml) for 30 h and the bacterial counts were obtained after 6, 24 and 30 h. The chemical profile of the crude extract was obtained using gas chromatography-mass spectrometry (GC-MS).

RESULTS

The reduction of Streptococcus mutans was concentration and exposure time dependent. The crude extract killed 48% of S. mutans at a lowest concentration of 0.1 mg/ml and 100% at 25 mg/ml after 6h. Biofilm formation was reduced by 95, 97 and 99% after 6, 24 and 30 h of exposure to the subinhibitory concentration of crude extract respectively. GC-MS analyses revealed the presence of polyphenols such as catechin or chromene groups, chalcones with trimethoxyphenyl group and tannin with 4-O-β-D-xylopyranoside. At high concentration the crude extract was bactericidal to Streptococcus mutans but subinhibitory concentration significantly reduced the planktonic cells and biofilm formation.

CONCLUSIONS

These results suggest that this plant has the potential to be used to control S. mutans and its biofilm which are responsible for oral infections.