Antibacterial effects of cinnamon, eucalyptus, and green tea extracts vs. chlorhexidine and their impact on efflux pump activity in Streptococcus

Dental caries is a common oral health challenge, and using antimicrobial agents like chlorhexidine gluconate is one approach to managing its progression, although its long-term application is limited by various side effects. Given that plant-based solutions such as cinnamon, eucalyptus, and green tea extracts offer promising antimicrobial effects, this study examines their potential as natural alternatives for preventing and managing dental caries. This in vitro study evaluates the antimicrobial activity of cinnamon, eucalyptus, and green tea extracts against Streptococcus mutans and Streptococcus sanguinis , comparing them with chlorhexidine. The minimum inhibitory concentration (MIC) of each agent, with and without the efflux pump inhibitor omeprazole, was determined using broth dilution and well diffusion methods. Chlorhexidine showed MIC values of 4 µg/mL and 2 µg/mL for Streptococcus mutans and Streptococcus sanguinis , respectively. Plant extracts exhibited MIC values with cinnamon at 375 µg/mL and 187 µg/ml. Well diffusion tests revealed increased inhibition zones when the efflux pump inhibitor was added. The study showed that 0.2% chlorhexidine had the strongest antibacterial effects against Streptococcus mutans and Streptococcus sanguinis , followed by green tea and cinnamon extracts. Green tea may serve as an alternative to chlorhexidine, potentially combined with efflux pump inhibitors to reduce resistance and side effects.