Report: Antibacterial and antibiofilm activities of Scorzonera mackmeliana

Scorzonera have been confirmed to have potent bioactivity. Scorzonera mackmeliana (Asteraceae), the endemic plant to Lebanon, has not yet been investigated. In the present study, we assessed the antibacterial activity of S. mackmeliana extracts against referenced bacterial strains. Extracts from different parts of the plant were evaluated against Staphylococcus, Enterococcus, Escherichia and Pseudomonas species. Phytochemical screening was done by standard biochemical tests and minimal inhibitory concentration (MIC), minimal bactericidal concentration (MBC) and minimal biofilm eradication concentration (MBEC) were determined by micro dilution method. The extracts possessed mainly alkaloids, phenols, flavonoids and coumarins. Gram-negative bacteria were most sensitive, whose MICs ranged between 48.98 and 341.85 mg/ml. Water stems extract, rich in phenols, was the most active with an MIC of 48.98 mg/ml. MBC was only recorded for water flowers extract, rich in resins, against P. aeruginosa and ethanolic roots extract, rich in terpenoids, against S. epidermidis with values of 160.85 mg/ml and 284.35 mg/ml, respectively. Furthermore, antibiofilm activity showed that the lowest MBEC was 0.1 mg/ml for water stems extract with an eradication ability of 91% (p< 0.0001). Hence, this study suggests S. mackmeliana as a promising candidate for future investigations to elucidate the major bioactive compound behind the antibacterial and antibiofilm effect.