Phytochemical study and antibacterial activity of Cedrus atlantica aerial part apolar extract

Phytochemical study of Cedrus atlantica aerial parts apolar extract led to the isolation of a new abietane diterpene (1), an abietane diterpene reported for the first time as a genuine natural product (2), two new megastigmane glycosides (3-4), and nine known compounds (5-13) including seven abietanes. Their structures were elucidated by 1D and 2D NMR spectroscopy and HRMS experiments. The crude extract was then evaluated through a broad screening against both Gram-positive and Gram-negative bacterial strains, with Staphylococcus epidermidis being the only affected microorganism. In a next step, a selection of pure compounds was also investigated and the diterpene 15-hydroxydehydroabietic acid (15-HDAA) (11) exhibited detectable antibacterial activity against S. epidermidis. Growth kinetics analysis revealed a clear modulation of bacterial growth at sub-MIC concentrations, indicating a measurable physiological impact on the bacterium. This effect, when combined, allows a significant reduction in the effective concentration of ampicillin.