Leaf essential oil of Juniperus oxycedrus L. (Cupressaceae) harvested in northern Tunisia: composition and intra-specific variability.

The essential oil composition of leaves of 60 individual trees of Juniperus oxycedrus L. growing in four locations in Tunisia harvested in three different seasons were investigated by GC and GC/MS. Seventy compounds were identified in the oils, and a relatively high variation in their contents were found. All the oils were dominated by terpenic hydrocarbons, with alpha-pinene (27.35-58.03%) as the main component, followed by geranyl acetone (13; 1.96-7.14%), 13-epimanoyl oxide (16; 1.35-6.95%), and eudesma-4(15),7-dien-1-ol (11; 1.39-4.18%). The 18 major oil components were processed by hierarchical clustering and principal component analysis (PCA) allowing to establish four groups, one divided into two subgroups, of populations according to the location and season of harvest. Their oils were differentiated by one compound or more, showing a clear seasonal and geographical polymorphism in their chemical composition allowing the identification of specific chemotypes. The pattern of geographic variation in the essential oil composition indicated that the oils of the populations from the continental site (Makthar) were clearly distinguished from those of the littoral localities (Tabarka, Hawaria, and Rimel).