Miguel, Maria GraçaDuarte, F.Venancio, F.Tavares, R.2015-06-152015-06-15200290-6605-875-70567-7572AUT: MGM00322;http://hdl.handle.net/10400.1/6350In the present work, the aerial parts of T. mastichina, were collected over a day period, during the flowering phase. The oil was isolated both from the fresh leaves and the fresh flowers by hydrodistillation and analysed by GC and GC/MS. Significant differences were registered between the content and composition of leaf oil and that of flower oil, while changes in consequence of the day period were less emphasised. The highest oil content was obtained from the flowers (2.0 and 2.2 %) at 12 h and 17 h, respectively. The major component of the essential oils was 1,8-cineole, present in higher amounts in the leaf oils than in the flower oils. Its minimal percentages detected in the leaf and the flower oils were 50.2 % and 46.7 %, respectively, observed at 23 h, while the maximal ones were 61.0 % and 50.2 %, at 12 h. Camphor, delta-terpineol + borneol and terpinen-4-ol were also present in higher amounts in the leaf oils than in the flower oils. In both oils, elevated concentrations of delta-terpineol + borneol were detected at 23 h (9.7 % and 8.2 %, respectively). The concentration of myrcene was ten times superior in the flower oils relatively to the leaf oils. In almost all samples, elemol was the sole sesquiterpene whose concentration exceeded 1.0 %.engconference object