1. Analysis of volatile fraction from selected thyme (Thymus L) species by means of GC-MS and HS-GC-MS D. Staszek1, M. Orłowska1, J. Rzepa1, G. Szymczak2, T. Kowalska1, M. Waksmundzka-Hajnos3 1Department of General Chemistry and Chromatography, Institute of Chemistry, University of Silesia, Katowice, Poland 2Botanical Garden, Maria Curie-Skłodowska University, Lublin, Poland 3Department of Inorganic Chemistry, Faculty of Pharmacy, Medical University of Lublin, Lublin, Poland  
I. Introduction
An influence of smells and aromas on psychical and physical condition of humans has been recognized a long time ago. In psychology and philosophy, aromatherapy is understood as a curative effect of essential oils, labeled as plant hormones, on human health [1,2]. Essential oils are the high-boiling liquids (boiling points thereof at ca. 105oC), known for their volatility. In chemical terms, essential oils are the mixtures of hydrocarbons, alcohols, aldehydes, ketones, esters and ethers, which belong to the group of terpenes (basically, mono- and sesquiterpenes), but they can also contain phenylpropane derivatives. Their activity can be quite differentiated such, as antibacterial, expectorant, sedative, and antipyretic. Essential oils can be isolated from plant material by hydrodistillation, extraction, pressing, etc. [3,4].
Common thyme (Thymus vulgaris L.) originates from the Mediterranean region. It is a tiny semi-shrub with characteristic, aromatic and nice smell of thymol.
It contains ca. 3.5% essential oils (occasionally up to 5.4%), up to 10% tannins, moreover, polyphenolic acids and flavonoids. Spectrum of its curative properties embraces expectorant, spasmolytic,
antifungal, and antibacterial activity [5,6].
II. Aim
It was an aim of this study to compare an efficiency of the two different methods of isolating essential oils (i.e., hydrodistillation followed by GC-MS and HS-GC-MS) for the following three thyme species: Thymus pulegioides, Thymus vulgaris and Thymus kosteleckyanus.
III. Experimental
Plant material employed in this study originated from Botanical Garden of The Maria Curie Sklodowska University In Lublin, Poland. Raw material consisted
of the three thyme species, i.e., Thymus pulegioides, Thymus vulgaris and Thymus kosteleckyanus. In this study, the volatile fraction originating from these three plant species was compared,
derived in two different ways. In case 1, the volatile fraction was isolated by means of hydrodistillation in the Deryng apparatus, followed by the GC-MS analysis. In case 2, the volatile fraction
was isolated and analyzed by means of the headspace-GC-MS technique.
A comparison of the chromatograms derived by means of the headspace desorption for the three different thyme species
Fig. 1. Chromatogram of a volatile fraction derived from Thymus vulgaris.
Fig. 2. Chromatogram of a volatile fraction derived from Thymus pulegioides.
Fig. 3. Chromatogram of a volatile fraction derived from Thymus kosteleckyanus.
A comparison of the chromatograms for essential oils isolated by means of the Deryng apparatus from the three different thyme species
Fig. 5. Chromatogram of a volatile fraction derived from Thymus pulegioides.
Fig. 6. Chromatogram of a volatile fraction derived from Thymus kosteleckyanus.
Fig. 4. Chromatogram of a volatile fraction derived from Thymus vulgaris.
Composition of essentials oils for the three different thyme species, as obtained with use of HS-GC-MS and GC-MS
Technics
2-methylbutanoic acid
α-thujene
α-pinene
camphene
sabinene
3-octanone
1-octen-3-ol
β-pinene
3-octanol
α-terpinene
D-limonene
mixture of isomers: p-cymene and o-cymene
eucalyptol
2-carene
γ-terpinene
β-terpineol
β-linalool
borneol
α-terpineol
2-isopropyl-5-methyl anisol
mixture of isomers:
thymol i carvacrol
caryophyllene
germacrene D
α-farnesene
α-nerolidol
spathulenol
HS-GC-MS
T. vulgaris  + -  +   - -
T. pulegioides
T. kosteleckyanus +
GC-MS
Volatile
compound
Species
 For essential oils originating from hydrodistillation, on the chromatograms the additional and intense peaks can be seen with the retention times ranging from 7.00 to 8.00 min. These compounds were identified as a mixture of p-xylene, m-xylene, and ethylbenzene, due to diluting the hydrodistilled essential oils with xylene for the analytical purpose.
IV. Conclusions
1) In terms of the numbers of isolated and identified compounds (qualitative analysis), HS-GC-MS proved more efficient than hydrodistillation followed by GC-MS.
2) The numbers of the identified compounds are comparable with all three analyzed thyme species, both when analyzed by means of HS-GC-MS and GC-MS. For HS-GC-MS, the obtained results are the following ones: T. vulgaris, 18 compounds; T. pulegioides, 17 compounds; T. kosteleckyanus, 18 compounds. For GC-MS, the obtained results are, as follows: T. vulgaris, 15 compounds; T. pulegioides, 15 compounds; T. kosteleckyanus, 14 compounds.
3) Composition of volatile fractions derived from T. vulgaris and T. pulegioides was similar, and that derived from T. kosteleckyanus was different from the former two.
V. References:
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[2] Aromaterapia: olejki eteryczne do pielęgnacji skóry, M.-C. Lapare, Warszawa, Bauer-Weltbild Media, 2005, str
[3] Krajowe rośliny olejkowe: występowanie, uprawa, skład chemiczny, zastosowanie, E. Pisulewska, Z. Janeczko, Kraków,
Know-How, 2008, str. 5-11
[4] Encyklopedia zielarstwa i ziołolecznictwa, H. Strzelecka, J. Kowalski, Warszawa, PWN, 2000, str
[5] Rośliny kosmetyczne, K. Jędrzejko, B. Kowalczyk, B. Bacler, Katowice, Wydaw. ŚAM, 2006, str
[6] Rośliny lecznicze i ich praktyczne zastosowanie, A. Ożarowski, W. Jaroniewski, Warszawa, Wydaw. IWZZ, 1987, str