Comparison of the Chemical Composition and Antimicrobial Activity of <i>Thymus serpyllum</i> Essential Oils

Abstract

The chemical composition of the essential oils obtained by hydrodistillation from the aerial parts of Thymus serpyllum and Thymus serpyllum ‘Aureus’ has been investigated by gas chromatography-mass spectrometry (GC-MS). Forty-seven compounds (99.67% of the total oil) were identified in the essential oil of T. serpyllum. The main components found in the oil were carvacrol (37.49%), γ-terpinene (10.79%), β-caryophyllene (6.51%), p-cymene (6.06%), (E)-β-ocimene (4.63%) and β-bisabolene (4.51%). Similarly, carvacrol (44.93%), γ-terpinene (10.08%), p-cymene (7.39%) and β-caryophyllene (6.77%) dominated in the oil of T. serpyllum ‘Aureus’. A total of forty three compounds were identified in this oil, representing 99.49% of the total oil content. On the basis of the obtained data it was proved that the content of 1-octen-3-ol, eucalyptol, (Z)-β-ocimene, (E)-β-ocimene, γ-terpinene, carvacrol methyl ether, germacrene D and β-bisabolene was significantly higher for T. serpyllum while T. serpyllum ‘Aureus’ was characterized by a significantly higher content of 3-octanone, 3-octanol, p-cymene, borneol and carvacrol. The isolated essential oils were evaluated for their antimicrobial activity against nine reference strains (Escherichia coli, Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus agalactiae, Enterococcus faecalis, Bacillus cereus, Micrococcus luteus, Proteus vulgaris and Candida albicans) by the microdilution technique. Based on this test, the minimum inhibitory concentrations (MIC) of essential oil were calculated. The volatile oil obtained from T. serpyllum showed the highest antimicrobial activity relative to the strain of E. coli (MIC=0.025 µL/mL) and to the yeast C. albicans (MIC=0.05 µL/mL). Similarly, a significant antimicrobial activity exhibited T. serpyllum ‘Aureus’ essential oil, although the MIC values obtained in that case for E. coli and C. albicans strains were twice as high and were respectively 0.05 µL/mL and 0.1 µL/mL.