Preliminary screening of pomegranate-derived compounds for antimicrobial and anti-virulence effects against cariogenic streptococci

As a biofilm-mediated disease, dental caries is primarily attributed to the activity of Streptococcus mutans and Streptococcus sobrinus, key contributors to enamel mineral loss under acidic conditions. Current broad-spectrum antimicrobials disrupt the oral microbiota and carry undesirable side effects, prompting interest in targeted, microbiome-friendly alternatives. This study evaluated the antimicrobial, anti-cariogenic, and cytotoxic properties of pomegranate (Punica granatum) derived compounds, corilagin, ellagic acid, gallocatechin, kaempferol-7-O-glucoside, punicalagin, punicalin, and rutin against cariogenic S. mutans and S. sobrinus, and the commensal S. gordonii. Antibacterial activity was assessed using disc diffusion, minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC) methods. Anti-virulence effects were evaluated through glycolytic pH drop and cell surface hydrophobicity assays. Cytotoxicity was determined using the brine shrimp lethality assay. Punicalagin, punicalin, and ellagic acid showed strong, selective bactericidal activity against S. mutans and S. sobrinus, with low MICs and MBC/MIC ratios, while sparing S. gordonii. These compounds significantly suppressed acid production, maintaining pH above the critical demineralisation threshold, and reduced surface hydrophobicity in cariogenic strains without affecting the commensal. Most compounds exhibited low toxicity (LC₅₀ > 500 µg/mL), indicating a favourable safety profile. Overall, punicalagin and punicalin demonstrated dual antimicrobial and anti-virulence activity with selective targeting of cariogenic pathogens. These findings support the potential inclusion of punicalagin and punicalin in oral care formulations aimed at preventing dental caries while preserving beneficial oral microbiota. As this is a preliminary screening study, the results should be interpreted cautiously, and further biofilm and host-cell assays are needed to confirm translational potential.