Study on variation of essential oil quality and quantity in dry and fresh herb of Thyme and Tarragon

Background: Thymus vulgaris L. belongs to Lamiaceae family that has 14 aromatic and perennial species, Tarragon (Artemisia dracunculus L.) belongs to Asteraceae family, this genus has 34 annual and perennial species. These two species aren't self growing in Iran but are cultivated. Widely use of two species (Thyme, Tarragon) essential oils in different industries indicate that, plant water content affects on yield and constituens of essential oil. Objective: To find out the essential oil quality and quantity in dry and fresh aerial parts of Thyme and Tarragon herbs. Method: The aerial parts of Thyme and Tarragon are collected in dry and fresh from. The essential oils extracted with Clevenger set by hydrodistillation method. The yield and constituens of essential oils were determined by GC/mass. Results: No variation between yield and constituents of essential oil of Tarragon was observed in fresh and dried herb at 35°C. The essential oil yield and constituents of dried Thyme at 35°C obviously decreased as compared to fresh herb. Conclusion: The yield and constituents of essential oil of tarragon herb are same in fresh and dried form but yield of constituents and essential oil in aerial part of thyme decreased in dried form.