Abstract

Thymus daenensis Celak. is an important medicinal plant grows in different climatic regions of Iran. A pot experiment was conducted to evaluate the essential oil yield and oil composition of thyme as affected by harvest time during 2010. Isolate the essential oil of the plant samples were determined by hydro-distillation in Clevenger Apparatus with three hours. Composition of the essential oils was determined by Gas chromatography mass spectrometry (GC-MS). Twenty six compounds, representing 98.5% of the essential oil were identified. The major compounds were thymol, p-cymene, γ-terpinene, β-caryophyllene and carvacrol. The results showed that thymol was the most abundant compound in thyme oil that a significant difference in its content due to harvest time was observed. The higher concentration of thymol was detected at full-flowering stage. In contrast, the higher concentration of γ-terpinene, a precursor of p-cymene, and p-cymene, a precursor of thymol was achieved at pre-flowering stage. Also, obtained results illustrated that phenolic compounds was higher in plant samples harvested at full-flowering stage. In addition, a significant increase in antioxidant activity of thyme was found to be due to harvest at full-flowering stage.

Key words: Thymus daenensis Celak., essential oil, hydro-distillation, gas chromatography mass spectrometry (GC-MS), harvest time.