Comparative chemical composition of the essential oil of Thymus vulgaris L. from different geographical sources
Variations in the essential oil composition of Thymus vulgaris L. cultivated in Estonia and in other European countries were determined using capillary gas chromatographic analysis methods. Fifty-nine components were identiﬁed, representing over 95% of the total oil yield. The principal components in the oils of common thyme were thymol (0.9%-75.7%), carvacrol (1.5%-83.5%), p-cymene (4.3%-34.4%), gamma-terpinene (0.9%19.7%), linalool (0.4%-4.8%), (E)-beta-caryophyllene (0.5%-9.3%) and terpinen-4-ol (tr.-3.8%). The sum of phenolic compounds (thymol and carvacrol) in the oils studied varied from 19.4% to 84.4%, and the sum of their precursors (p-cymene and gamma-terpinene) ranged from 5.7% to 38.5%. Thymol content was predominant in the oils of Holland (65.5%) and of Estonia (75.7%) but carvacrol content predominated in the Greek thyme oil (83.5%). Armenian thyme oil contained only 17.0% of thymol, but it was rich in neral and citronellol (32.5%), borneol (4.3%), citronellal (4.0%), 1,8-cineol (4.0%) and methyl eugenol and thymol acetate (7.5%). In Estonia, the thymol, thymol-carvacrol and thymol-p-cymene-gamma-terpinene chemotypes of the common thyme are distinguishable.