Comparison of volatile constituents, and antioxidant and antibacterial activities of the essential oils of Thymus caucasicus, T. kotschyanus and T. vulgaris

A comparison of the chemical composition, and antioxidant and antibacterial activities of the essential oils obtained from the aerial parts of Thymus caucasicus, T. kotschyanus, and T vulgaris was carried out. The oils, obtained by hydrodistillation, were analyzed by GC and GC/MS. Twenty, 29 and 22 compounds representing 94.8%, 96.6% and 98.2% of the essential oils of T. caucasicus, T. kotschyanus and T. vulgaris, respectively, have been identified. The oil of T. caucasicus was characterized by 1,8-cineol (21.5%), thymol (12.6%), beta-fenchyl alcohol (8.7%), nerolidol (7.8%), terpinolene (7.2%), alpha-pinene (7.0%) and myrcene (6.8%). In the oil of T. kotschyanus, carvacrol (24.4%), beta-caryophyllene (14.5%), gamma-terpinene (12.4%), alpha-phellandrene (10.8%), p-cymene (9.8%) and thymol (6.8%) were the predominant compounds, whereas the main components of T. vulgaris oil were thymol (43.8%), p-cymene (15.2%), germacrene-D (11.7%), terpinolene (3.4%), carvacrol (3.2%), beta-caryophyllene (2.8%) and alpha-thujene (2.2%). In all three plants oil, hydrocarbon monoterpenes predominated over sesquiterpenes. Antioxidant activities were assessed by determining IC50 values in the DPPH radical scavenging assay. Antibacterial activity was determined by measuring minimum inhibitory concentration (MIC) using the broth dilution method. The essential oils of T. caucasicus, T. kotschyanus and T. vulgaris showed free radical scavenging and antibacterial activity.