Antimicrobial Potential of Salvadora persica Stem Extract Against Dental Plaque-Associated Microorganisms: An Integrated In vitro and Molecular Docking Study

Abstract

The increasing prevalence of antimicrobial resistance and oral biofilm-associated diseases has intensified the search for alternative therapeutic agents from medicinal plants. Salvadora persica L. (miswak) has long been employed in traditional oral hygiene owing to its antimicrobial properties; however, the molecular mechanisms underlying its antibacterial activity remain incompletely understood. This study investigated the antimicrobial activity of the methanolic stem extract of S. persica against selected oral pathogens and explored the inhibitory potential of its phytochemical constituents against bacterial DNA gyrase using molecular docking. Methanolic stem extract of S. persica was prepared by cold maceration and qualitatively screened for phytochemical constituents. Antimicrobial activity against Staphylococcus aureus, Escherichia coli, and Aspergillus niger was evaluated using the agar well diffusion assay, while the minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and minimum fungicidal concentration (MFC) were determined using standard microbiological methods. Identified phytochemicals were subsequently subjected to molecular docking against Escherichia coli DNA gyrase subunits A and B (PDB ID: 3NUH), using levofloxacin as the reference inhibitor. Protein–ligand interactions were analyzed using Discovery Studio Visualizer and PyMOL. Phytochemical screening revealed the presence of flavonoids, alkaloids, tannins, saponins, terpenoids, anthraquinones, phenols, and cardiac glycosides. The extract exhibited concentration-dependent antimicrobial activity against all tested organisms, with the highest inhibition observed against S. aureus (22.1 mm), followed by A. niger (18.6 mm) and E. coli (15.4 mm) at 100 mg/mL. The MIC and MBC values against the bacterial isolates were 12.5 mg/mL and 25 mg/mL, respectively, while the MFC against A. niger was 50 mg/mL. Molecular docking identified the compound with PubChem CID 135580681 as the most promising ligand, exhibiting stronger binding affinities toward DNA gyrase subunit A (−8.0 kcal/mol) and subunit B (−7.6 kcal/mol) than the reference inhibitor levofloxacin (−6.1 and −6.8 kcal/mol, respectively). Interaction analysis demonstrated that the compound formed favorable hydrogen-bonding, hydrophobic, and electrostatic interactions with key active-site residues involved in enzyme inhibition. The methanolic stem extract of Salvadora persica possesses significant antimicrobial activity against selected oral pathogens and contains bioactive phytochemicals with promising inhibitory activity against bacterial DNA gyrase. These findings provide mechanistic support for the traditional use of S. persica in oral healthcare and identify PubChem CID 135580681 as a potential lead compound for the development of novel therapeutics targeting dental plaque-associated bacterial infections. However, further toxicity evaluation, molecular dynamics simulations, and experimental validation may be needed to further confirm this data. 

Antimicrobial Potential of Salvadora persica Stem Extract Against Dental Plaque-Associated Microorganisms: An Integrated In vitro and Molecular Docking Study