Antimicrobial synergy of Salvadora persica, clove, and propolis against oral pathogens: Relevance to dental applications

ABSTRACT Background: The use of natural plant extracts to combat pathogenic bacteria offers a promising approach to preventing microbial resistance. This study explores the synergistic antimicrobial effects of Salvadora persica , propolis, and clove extracts against Candida albicans and Streptococcus mutans . Materials and Methods: This was an in vitro experimental study designed to evaluate the antimicrobial activity and synergistic interactions of ethanol extracts of S. persica , clove, and propolis against S. mutans and C. albicans using agar dilution and checkerboard assays. The chemical composition of the extracts was analyzed using Soxhlet and accelerated solvent extraction methods, followed by gas chromatography–mass spectrometry analysis. Results: The minimum inhibitory concentration values for S. persica , clove, and propolis against S. mutans were 4.5 mg/ml, 9 mg/ml, and 2.2 mg/ml, respectively, and for C. albicans , 4.5 mg/ml for S. persica and clove, and 1.1 mg/ml for propolis. Combinations of these extracts demonstrated synergistic effects with fractional inhibitory concentration indexes ranging from 0.3 to 1.5 against both pathogens. Conclusion: These results suggest that combining plant extracts with propolis may offer an effective strategy for treating oral infections. Given the role of S. mutans in dental caries, these findings support the potential use of these natural compounds in preventive and therapeutic dental applications.