Phytochemical Investigation and Antimicrobial Activity of Galium libanoticum

This study represents the first report of phytochemical investigation and antimicrobial screening of Galium libanoticum endemic to Lebanon. Despite the presence of more than 700 species of the genus Galium, this plant has not been investigated previously. Plants of the genus Galium are well known traditionally for their antioxidant, anti-inflammatory, diuretic, and antimicrobial activities. In this study, we aimed to carry out, for the first time, the phytochemical investigation of G. libanoticum that has not been explored previously.

Isolation of bioactive compounds was performed using different chromatographic techniques, and the structure identification was achieved using 1H-NMR, 13C-NMR, and 2D NMR spectroscopy.

Results revealed two major components, rutin (1) and asperulosidic acid (2). Both compounds, as well as the crude extract, were evaluated for their antibacterial activity against some common strains. The plant extract showed significant activity against Gram-positive bacteria E. faecalis and S. aureus with MIC of 31.25 μg/mL and 62.5 μg/mL, respectively.

This antibacterial activity was higher than that reported from other Galium species, suggesting special chemotypes with different constituents that should be investigated. On the other hand, rutin and asperulosidic acid revealed the highest activity against Gram-negative bacteria.

This study highlighted the medicinal potential of the Galium libanoticum plant and its metabolites and necessitated further studies to isolate the undiscovered constituents that could serve as potential therapeutic remedies, especially in the antimicrobial resistance.