The effects of drying methods on essential oil content and composition of Thymus daenensis Celak

Thymus species are well known as medicinal plants because of having biological and pharmacological properties. Thymus daenensis is an endemic aromatic medicinal plant to Iran. Essential oil of Thymus daenensis is a rich source of thymol which gives high antimicrobial and antioxidant activity to this plant. In this research, the aerial parts of Thymus daenensis were collected at full flowering stage from Alborz Research Station in Karaj. For finding the effect of drying methods on essential oil yield and composition, the plant material were dried in four different conditions (oven 30°C, 40°C, 50°C and shade). After drying the samples, their essential oils were obtained by water distillation in three replications and were analyzed by GC and GC/MS. Oil yield and percentage of main components were statistically compared by Duncan's test in SAS software. Oil yields (w/w) of the oven-dried 30°C, 40°C, 50°C and shade-dried samples were 1.42%, 1.12%, 1.24% and 1.29%, respectively. Thymol (75.3%, 75.7%, 72.0% and 67.2%), allo-aromadendrene (5.7%, 5.2%, 5.4% and 3.9%), γ-terpinene (2.9%, 2.8%, 5.9% and 10.2%), p-cymene (4.2%, 4.1%, 5.1% and 5.5%) and carvacrol (2.2%, 4.1%, 1.6% and 2.4%) were identified as the main components in oven-dried 30°C, 40°C, 50°C and shade-dried samples, respectively. Statistical analysis showed a significant difference between oil yields of oven-dried 30°C sample with other samples. The highest percentage of thymol was obtained from oven-dried 30°C and 40°C that showed a significant difference with other drying methods.