Exploring Medicinal Plants for Antimicrobial Activity and Synergistic Effects With Doxycycline Against Bacterial Species.

Medicinal plants are rich sources of bioactive compounds with diverse pharmacological properties, including antimicrobial activities. This study aimed to assess the antibiofilm potential of methanol and ethanol extracts from nine selected medicinal plants, as well as their synergistic effects with doxycycline against strains. Standard procedures were employed to determine the phytochemical composition, total phenolic, and flavonoid contents of the extracts. The antibacterial activity was evaluated using the broth microdilution method, while biofilm formation was assessed via the microtiter plate method. Antibiofilm activity was determined using the 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium-bromide (MTT) assay. Combination studies were conducted using the checkerboard microdilution method. All extracts contained phenols, flavonoids, steroids, triterpenes, and anthraquinones. The methanolic extract of exhibited the highest total phenolic and flavonoid contents (90.48 ± 0.55 mg GAE/g), while the ethanolic extract of showed the highest flavonoid content (6.48 ± 0.33 mg QE/g). Ethanol extracts of and and methanolic extract of demonstrated significant antibacterial activity against 34F2 Sterne strains, with a MIC value of 64 g/mL. Biofilm formation in strains was notably enhanced in the presence of glucose. The methanolic extract of exhibited the highest biofilm imbibition (85%), while methanolic extract showed the most effective biofilm eradication (79%). The combination of ethanol extract with doxycycline displayed synergistic effects against biofilm formation inhibition and eradication in all tested strains. Taken together, ethanol extract shows promise for developing new combination antibacterial therapies.