Phytochemical Screening and Dual Antimicrobial–Antibiofilm Activities of Platanus orientalis Linn Methanolic Leaf Extract Against Multidrug-Resistant Salmonella enterica and Shigella flexneri

Abstract

Antimicrobial resistance among multidrug-resistant enteric pathogens, such as Salmonella enterica and Shigella flexneri, poses a critical global health challenge, necessitating novel therapeutic strategies from natural sources. This study evaluated the preliminary phytochemical profile and dual antibacterial and antibiofilm activities of methanolic leaf extract from Platanus orientalis Linn. Qualitative and quantitative phytochemical analyses were conducted to assess phenolic and flavonoid contents, while antibacterial activity against multidrug-resistant isolates was determined using broth microdilution to obtain minimum inhibitory concentrations (MICs). Antibiofilm effects were examined at sub-MIC concentrations via the crystal violet assay. The extract was found to be rich in phenolics and flavonoids and exhibited concentration-dependent antibacterial activity, with MICs of 64 µg/mL for S. enterica and 32 µg/mL for S. flexneri. Sub-MIC concentrations significantly reduced biofilm biomass by 60–80%, likely through interference with quorum sensing and extracellular polymeric substance production. These results highlight the extract’s potential as a phytotherapeutic agent targeting both planktonic cells and biofilms, providing insights for the development of natural antimicrobials against resistant enteric pathogens. Overall, the findings underscore the potential of Platanus orientalis methanolic leaf extract as a promising natural antibacterial and antibiofilm agent against multidrug-resistant enteric pathogens and support its further development as an alternative or complementary therapeutic strategy. It should be noted that the phytochemical results are qualitative and indicative, and further LC–MS or NMR analyses are required for definitive compound identification.