Composition and yield of the essential oils from whole plant, leaves and branches of Rosmarinus officinalis L. growing in minor islands of “Parco Nazionale dell’Arcipelago Toscano”

The ecology of the small islands of the Tuscany Archipelago is very characteristic and different from the continental habitats; the island biotypes are very limited in quality and extension. The “island” effect is the main influence on the natural environment due to the geographic isolation. The ecosystems are strongly isolated; both the unfavorable climatic conditions and the poor summer moisture, the remarkable exposure to strong winds transporting salts, and the absence of an abundant and deep soil create difficult conditions for many species, both plants and animals, creating limits for those specifically adapted, too. The variability of the secondary metabolites and, among these, the essential oil constituents, depends on problems linked to their survival. The plants of the Tuscany Archipelago could have a particular secondary metabolism and a patrimony of biodiversity to protect and to conserve. The aim of this study was to evaluate the yield and the chemical composition of the essential oil of Rosmarinus officinalis L. originating from the entire plant, from the leaves or from the branches collected from wild material. In all the essential oil samples, alpha-pinene, 1,8-cineole and camphor, were detected in higher percentages in the leaves than in the branches. By contrast, borneol and isobornyl acetate were much more represented in the branches. The essential oil of the tops resulted from the combination of the oil from leaves and branches, even if the very low yield of the branches must be considered. The yields of the essential oils from the leaves were always high, comprising between 1.5% and 3.6%, whereas for the branches they varied from trace amounts to about 0.3%.