Rhodiola rosea extract inhibits the biofilm formation and the expression of virulence genes of cariogenic oral pathogen Streptococcus mutans.

The present study aimed to evaluate the effect of Rhodiola rosea extract (RE) on Streptococcus mutans biofilm formation and the relevant mechanism of its action. The effect of RE on the biofilm formation and extracellular polysaccharides (EPS) synthesis of S. mutans was assessed by confocal laser scanning microscopy (CLSM), crystal violet staining and CFU counting method. Scanning electron microscopy (SEM) was applied to observe the surface morphology of S. mutans biofilms formed on glass coverslips and dental enamel. To study the relevant mechanism, quantitative real time PCR (qRT-PCR) and zymogram assay were applied to measure the expression of virulence genes and the enzymatic activity of glucosyltransferases (Gtfs) under the treatment of RE. The CCK-8 assay was also performed on macrophages (RAWs) and human oral keratinocytes (HOKs) in order to evaluate its biocompatibility. As a result, RE inhibited the biofilm formation and EPS synthesis of S. mutans. RE also suppressed the expression of gtf genes and quorum sensing (QS) system as well as the enzymatic activity of Gtf proteins. Moreover, RE exhibited a good biocompatibility to human cells. This study provides the evidence for RE as a novel anti-biofilm agent for clinical use.