Comparative analysis of content and composition of essential oils of Thymus vulgaris L. from different regions of Europe

Abstract

Common thyme (Thymus vulgaris L., Lamiaceae) is one of the most well-known plants in the world, widely used in medicine, culinary arts, and cosmetics. The aim of this study was to analyse the content and composition of essential oils (EO) obtained from the T. vulgaris commercial samples grown in Estonia and in various European countries. Gas chromatography was used to characterize the quality and diversity of chemotypes of the studied plant raw material of different origins. The samples of the T. vulgaris herb contained 3–28 mL/kg of EO, and in five samples it was below the European Pharmacopoeia (Ph. Eur.) requirement (minimum 12 mL/kg). In total, 44 EO compounds were identified in the essential oils of the studied T. vulgaris samples. Among them, five principal compounds were carvacrol (2.3–87.5%), thymol (0.9–71.2%), p-cymene (0.3–26.0%), γ-terpinene (0.1–16.1%), and (E)-β-caryophyllene (0.6–9.2%). It was concluded that the main compound of T. vulgaris EO (n = 37) was thymol with an average content of 41.1%. Monoterpenoids (90.5%) and sesquiterpenoids (5.7%) were the most dominating groups of terpenoids in the studied EO. Regarding the minimum and maximum content of key compounds in EO, none of the studied samples (n = 22) fully met the requirements of Ph. Eur. 11. The content of the four most important terpenoids (thymol, carvacrol, p-cymene, and γ-terpinene) in the EO of T. vulgaris does not change much from the beginning to the end of the flowering period. Correlations between the content of the most important (>2%) components (n = 14) of the studied EO (n = 37) showed a level >0.9 in several cases. Among seven studied chemotypes of T. vulgaris EO, five contained thymol as one of the main components.

Keywords

• common thyme
• gas chromatography
• chemotype
• thymol
• carvacrol
• p­-cymene
• γ­-terpinene.