Method: Minimum inhibitory concentration (MIC) were performed by microtechnique using 96-well microplates, brain heart infusion broth and inoculum 105 CFU/mL. The inhibition of adherence assessments were carried out using 96-well microplates. Biofilms were established using the 6-well plates.
Result: Extracts of Juniperus communis, Myristica fragrans and Azadirachta indica showed strong antimicrobial activity against streptococci, with MIC ranging from 125 to 500 μg/mL. The Sida cordifolia showed no antimicrobial activity against the microorganisms studied and was not able to inhibit the adhesion of Streptococcus mutans and Streptococcus sobrinus. The Juniperus communis inhibited 50% to 100% of adherence of Streptococcus mutans in a concentration of 500 μg/mL to 1000 μg/mL respectively. The Streptococcus sobrinus adhesion inhibition occurred at concentrations of 125 μg/mL. The Myristica fragans inhibited the adhesion of Streptococcus mutans from the concentration of 62.5 μg/mL. The percentage of inhibition was 60% to 100% at a concentration of 250 μg/mL to 1000 μg/mL respectively. It was able to inhibit 100% of the adhesion of Streptococcus sobrinus at concentration of 250 μg/mL. Azadirachta indica inhibited adherence of Streptococcus mutans and Streptococcus sobrinus from the concentration of 1000 μg/mL. It was also able to reduce the amount of bacteria in biofilms of Streptococcus mutans in a concentration of 4000 μg/mL after 5 minutes exposure.
Conclusion: The elucidation of the antimicrobial activity of medicinal plants against a group of microorganisms in particular, contributes significantly to guide the proper use of herbal medicines, especially in dentistry.