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: ), 2 new megastigmane glycosides (3: -4: ), and 9 known compounds (5: -13: ), including 7 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: ) was shown to exhibit detectable antibacterial activity against S. epidermidis. Growth kinetics analysis revealed a clear modulation of bacterial growth at sub-minimum inhibitory concentration (MIC), indicating a measurable physiological impact on the bacterium. This effect, when combined, allows a significant reduction in the effective concentration of ampicillin.