Antibacterial activity of methanolic and aqueous extracts of Ligaria cuneifolia and Tripodhantus flagellaris.

Ligaria cuneifolia, and Tripodanthus flagellaris are two species belonging to the Loranthaceae family which is widely distributed in the central and northern areas of the Argentina Republic. The present study was conduced to test the antibacterial activity of aqueous and methanol extracts of both plants against Staphylococcus aureus ATCC 43300, Staphylococcus aureus ATCC 25923, Listeria monocytogenes CLIP 74910, Escherichia coli ATCC 35218 and Pseudomona aeruginosa ATCC 27853 strains. Antibacterial activity was determined using the agar diffusion method (variant holes) and the minimum inhibitory concentration (MIC) by broth microdilution test at concentration ranges from 5000 to 156.25 μg/mL. The greatest effect was observed for the aqueous and methanol extracts of T. flagellaris against S. aureus and L. monocytogenes for which the average diameters of the zones of inhibition were 15 to 16 mm and the MIC values were 625 to 312.5 μg/ml. Considering the CBM / MIC ratio, MIC values of T. flagelaris aqueous extracts and MIC values of both extracts of L. cuneifolia showed bactericidal effect against L. monocytogenes. Also, both extracts of L. cuneifolia showed bactericidal effect against this bacterial species (2500 µg/mL) and bacteriostatic effect against S. aureus. These preliminary findings demonstrate the antibacterial activity of both plants and contribute to improve the knowledge of these species, reinforcing the importance of the ethnobotanical approach as a potential source of new bioactive substances.