Chemical composition of the essential oils from Thymus mastichina over a day period
2003
Miguel, M.G. | Duarte, F. | Venancio, F. | Tavares, R.
In the present work, the aerial parts of T. mastichina maintained in pots, on a sandy soil and fertilized every fifteen days with a solution 1:3:1 (N:P:K) and 0.4 % Mg, were collected over a day period, during the flowering phase. The oils were isolated from both the fresh leaves and the fresh flowers by hydrodistillation and analyzed by GC and GC/MS. The highest oil yields were obtained from the flowers, the highest ones (2.0 % and 2.2 %, v/w) being observed when the flowers were collected 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. The minimal percentages detected in the leaf and the flower oils were 50.2 % and 46.7 %, respectively, observed at 23 h, while the maxi-mal ones were 61.0 % and 50.2 %, at 12 h. Camphor, δ-terpineol+borneol and terpinen-4-ol were also in higher amounts in the leaf oils than in the flower oils. In both the leaf and the flower oils, more elevated concentrations of δ-terpineol+borneol were detected at 23 h (9.7 % and 8.2 %, respectively). α-Pinene, camphene, sabinene and β-pinene were the monoterpene hydrocarbons whose concentrations exceeded 1.0 %. The flower oils were richer in α-pinene, sabinene, β-pinene and myrcene than the leaf oils. The most im-portant quantitative difference was observed for myrcene. The concentration of this compound was ten times superior in the flower oils relative to the leaf oils. Higher levels of p-cymene were observed in the leaf oils than in the flower oils. In almost all samples, elemol was the sole sesquiterpene whose concentration exceeded 1.0 %.
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