Composition of the essential oils from Portuguese Thymus albicans collected at different regions of Ria Formosa (Algarve)

The chemical composition of the essential oils from the leaves and the flowers of Thymus albicans Hoffin. et Link collected at three regions of Algarve, south of Portugal, was analyzed by GC and GUMS. The oils isolated from the flowers and the leaves were obtained in similar yields, 4.3% (v/w) and 4.2% (v/w), in the samples from Quinta do Lago, and 3.5% and 3.6%, in the samples from Ancao, respectively. in contrast, the oil yields from Gambelas ranged from 5.7%, in the leaf oils, to 9.2%, in the flower oils. The oils isolated from all samples of leaves and flowers were dominated by the oxygenated monoterpene 1,8-cineole (42.1-67.9%). in the samples collected at Quinta do Lago, high levels of linalool were also found (30.3-36.9%). The major monoterpene hydrocarbons in all samples were alpha-pinene (1.7-4.3%), sabinene (1.6-3.4%) and beta-pinene (2.6-4.9%). The concentrations of a-pinene (1.7-1.8%), camphene (0.2%) and beta-pinene (2.6-2.9%) in the samples from Quinta do Lago were in lower amounts than in the remaining samples. The most representative sesquiterpene hydrocarbons were beta-elemene (0.2-0.7%), beta-caryophyllene (0.1-0.8%) and gamma-cadinene (0.2-0.5%). The oxygenated sesquiterpene that was always present in higher amounts in the leaf oils than in the respective flower oils was viridiflorol (0.4-1.0%), the most important compound belonging to this fraction. The previous separation of the leaves and the flowers from this species evidenced the existence of quantitative differences in some components according to the plant part used. Still, for the same chemotype there were quantitative differences in some components, showing the existence of some variability demanding a more careful study to explain it