COMPOSITION AND VARIABILITY OF THE ESSENTIAL OILS OF THYMUS SPECIES FROM SECTION MASTICHINA FROM PORTUGAL

The composition and chemical polymorphism of the essential oils of sev eral populations of Thymus mastichina subsp. mastichina, T. mastichina subsp, donyanae and T. albicans, which belong to the Section Mastichi na of the genus Thymus, were investigated by GC and GC-MS. Ail represe ntative population samples of these three taxa were characterized by t heir high 1,8-cineole content, which is a discriminatory and common fe ature of the essential oils of the Section Mastichina. Linalool is ano ther major constituent of the essential oils of some populations of T. mastichina subsp, mastichina and T. albicans. The essential oil of T. masfichina subsp. donyanae is also characterized by large amounts of borneol. This feature distinguishes its essential oil from the type su bspecies. To study the infraspecific variability of each taxon, the re sults obtained in the GC analyses of the volatile oil of several indiv idual plants from each population were submitted to a Principal Compon ent Analysis and a Cluster Analysis, which showed that the essential o ils of the only population investigated of T. mastichina subsp, donyan ae have no chemical polymorphism, whereas the oils of T. mastichina su bsp, masfichina and T. albicans have infraspecific variability. Some c orrelation between the amount of linalool in the essential oil of T. m astichina subsp. masfichina and the Atlantic humidity was established. (C) 1997 Elsevier Science Ltd.