Influence of plant extracts on the growth of oral pathogens Streptococcus mutans and Candida albicans in vitro

Abstract

The objective of this study was to investigative the effects of ten plant extracts, six juices, and propolis and their combinations on the in vitro growth of oral pathogens Streptococcus mutans and Candida albicans. Agar-well diffusion and broth dilution methods were used. Triple and quadruple combinations were tested with the most active extracts. All of the tested 70% ethanolic extracts inhibited the growth of S. mutans and C. albicans. Cloves, cinnamon, propolis, lavender, and sage were the most active inhibitors. Apple, black chokeberry, black elderberry, cranberry, Japanese quince, and lemon juice demonstrated little activity. Mixed in double 1: 1 combinations, 8 extract combinations expressed synergistic action and 11 combinations expressed antagonistic action to the inhibition of the growth of C. albicans. Chamomile, liquorice, marigold, and lavender were involved both in synergistic and antagonistic interactions depending on the second component of the mixture. Propolis, cinnamon, and cloves were involved only in particular synergistic interactions, while sweet flag, dog rose, and oregano related only to some antagonistic interactions. The most active quadruple combination consisted of cloves, cinnamon, propolis, and lavender. Moreover, it demonstrated activity and synergistic action against both microorganisms. Propolis and all the studied plant extracts may be of great interest for inhibiting the growth of oral pathogens S. mutans and C. albicans.