Development of a herbal mouthwash containing a mixture of essential oils and plant extracts and in vitro testing of its antimicrobial efficiency against the planktonic and biofilm-enclosed cariogenic bacterium Streptococcus mutans

Abstract

A herbal mouthwash containing essential oils of holy basil and mountain tea, extracts of St John’s wort and European goldenrod (Bucovia™) and cetylpyridinium chloride, was developed and in vitro tested for its efficiency against biofilm formation by Streptococcus mutans, together with its eradicating activity against already preformed (48 h with saccharose) streptococcal biofilm. The minimum inhibitory (MIC) and bactericidal concentrations (MBC) of the final formulation, as well as of its individual components, were initially determined. The results revealed that the mouthwash needed to be applied at two-times its MIC (0.63% v.v⁻¹) to completely inhibit biofilm formation by S. mutans, which was otherwise capable of developing a robust biofilm on the tested surface. Once fully developed, the matrix of the biofilm was found to contain a significant amount of exopolysaccharides protecting the cells, being impossible to eradicate even when exposed to pure mouthwash for 15 min, highlighting the great recalcitrance of biofilm-embedded S. mutans.

Graphical Abstract

Keywords:

• Streptococcus mutans
• dental plaque
• mouthwash
• antimicrobial phytochemicals
• essential oils
• biofilm exopolysaccharides

Disclosure statement

This research did not receive any specific grant from funding agencies in the public, commercial or not-for-profit sectors. The authors PA and KV are employee and owner, respectively, of the NuCLab, which is a private R&D laboratory devoted to the development of cosmetic products and nutritional supplements.

Data availability statement

The data that support the findings of this study are available from the corresponding author, [EG], upon reasonable request.