Chemical composition and biological activity of essential oil of the Moroccan endemic Origanum grosii

The aim of this research was to study the chemical composition and biological activity of essential oil of the Moroccan endemic Origanum grosii on biofilm of Staphylococcus aureus strains. Qualitative and quantitative composition of the essential oil was analyzed by gas chromatography and gas chromatography-mass spectrometry. The Minimum Inhibitory Concentration was determined using the broth microdilution method. Phytochemical analyses revealed a high content of carvacrol, p-cymene, γ-terpinene and thymol. The antibiofilm effect of essential oil of Origanum grosii was tested against three staphylococcal strains (Staphylococcus aureus MBLA, Staphylococcus aureus CECT976 and Staphylococcus aureus ATCC25923). Results showed that the Minimum Inhibitory Concentration are lower than the Minimum Bactericidal Concentration (MBC = 2 MIC), hence the bacteriostatic power of this essential oil. In fact, essential oil of Origanum grosii presented a high antibiofilm effect against different staphylococcal strains by the inhibition of the biofilm formation and showed also a significant antibacterial activity (dose-dependent), since it increases with the increase in the concentration of this essential oil. The use of essential oil of Origanum grosii as natural antibacterial agent may effectively inhibit the growth of biofilm of medical relevance. Results indicated also that essential oil of Origanum grosii may be a potential alternative against Staphylococcus resistant strains. For this reason, the essential oil of Origanum grosii can be a promising alternative for both microbial control and therapeutic treatment against pathogenic resistant bacteria. Nevertheless, further studies should be conducted in order to elucidate the mechanisms of action of the essential oil on the bacterial cells under study. © 2022