Effect of bioclimatic area on the essential oil composition and antibacterial activity of Rosmarinus officinalis L.

The essential oil yield, volatile profile and antimicrobial activity of individual Rosmarinus officinalis L. shrubs growing wild in the different bioclimatic areas of the province of Murcia (Spain) were studied. A low thermicity index favoured the production of essential oil; however, no differentiation related to a specific chemotype depended on the geographical origin.In individual plants, the effect of the order of abundance among the components that define the rosemary essential oil chemotype (eucalyptol, camphor, α-pinene), on the antimicrobial activity was also determined. All the chemotypes showed strong antibacterial activity against four food-borne pathogens.Determination of the diameter of inhibition in Salmonella typhimurium pointed to a positive contribution effect of eucalyptol and α-pinene. A high proportion of α-pinene increases the effectiveness of the oil against Staphylococcus aureus, while the presence of eucalyptol, as the most abundant compound, considerably decreases the efficiency of rosemary oil. In contrast, the efficacy of these oils against Listeria monocytogenes and Escherichia coli was not affected by this condition.As regards the minimum inhibitory (MIC) and bactericide (MBC) concentrations, the strong activities exhibited by these essentials oils (<0.5 μL/mL) did not allow the chemotypes and antibacterial activities to be differentiated.

► Essential oil production is favoured in areas with a low thermicity index.
► Chemotypes do not depend on the geographical origin.
► The essential oil chemotype defines the bactericidal efficacy of Rosemary.