The potency of herbal extracts and its green synthesized nanoparticle formulation as antibacterial agents against Streptococcus mutans associated biofilms

•The ethanolic extracts of S. asper, S. aromaticum, and C. citratus exhibited antibacterial activities against S. mutans by reducing the bacterial biofilm formation and decreasing S. mutans cell surface hydrophobicity which affects the bacterial attachment and infection.•The 3D structural interactions between GtfB amino acids and the luteolin compound of C. citratus showed a high docking score, working as a biofilm inhibitor in this study.•The application of the AgNPs formulated from the herbal extracts showed potential effects on modifying bacterial biofilm structure. This study aims to determine the effects of the extracts of Streblus asper, Cymbopogon citratus, Syzygium aromaticum and its formulation of green synthesized silver nanoparticle (AgNPs) on Streptococcus mutans growth and biofilm formation. The ethanolic extracts of S. asper, C. citratus, S. aromaticum, and a mix of the three herbs demonstrated antibacterial activity against S. mutans isolates by reducing bacterial biofilm formation and decreasing bacterial cell surface hydrophobicity. The formulated AgNPs from the ethanolic extracts could enhance the antibacterial activities of the plant extracts. Molecular docking found the best interaction between luteolin isolated from C. citratus and glucosyltransferase protein (GtfB), assuming the promising anti-biofilm activity. The scanning electron microscopy revealed morphological changes in the biofilm structure and a significant decrease in the biofilm area of the AgNPs treated. The study suggested that the extracts and its application could be used as natural alternative agents with multi-action against S. mutans infections.