Essential Oil Polymorphism in Finnish Thymus Species

Abstract

Chemical polymorphism concerning the essential oils of the genus Thymus is a widespread phenomenon, especially in the northern species. The two Finnish species, T. serpyllum ssp. serpyllum and T. serpyllum ssp. tanaenis, turned out to form four different chemotypes each, with hedycaryol, germacra-1(10),5-dien-4-ol, germacra-1(10),4-dien-6-ol, linalool, and linalyl acetate as type-characterizing compounds. Otherwise the oils of the two subspecies were similar containing myrcene, trans-β-ocimene, β-caryophyllene, and germacrene D as the main terpene hydrocarbons. 1,8-Cineol and camphor represented another great portion in both oils.

If Finland is regarded as an area of T. serpyllum (s.l.), a total of six types of plants can be defined with regard to the essential oil chemistry only. Including the frequency of these six types at the four areas investigated, a certain gradient from the south to the north can be seen. A most interesting aspect is the fact that the most frequent, linalyl acetate containing chemotype of the northern Lapland has nearly the same oil composition as T. praecox ssp. arcticus in Island, Norway, and Greenland.

Key words

Essential oil polymorphism - Thymus species - chemotypes