seasonal variation of mono- and sesquiterpenoid components in the essential oil of dracocephalum kotschyi boiss.

background and objectives: dracocephalum kotschyi is a plant which belongs to the lamiaceae family and exists mostly in south-west asian countries, including iran. this plant is used as antispasmodic, analgesic and anti-inflammatory to treat rheumatoid diseases. methods: in order to investigate the impact of the harvesting time changes on the quantity and quality of mono- and sesquiterpenoid components of d. kotschyi aerial parts, ten samples were collected from cultivated plants from 19 april to 27 august 2013. also samples of flower and root were harvested in order to investigate their essential oil components. the essential oils were obtained through hydrodistillation method. the components were studied and identified by gc and gc ⁄ ms systems. results: the highest yield of the essential oil was obtained on 3 may (1.10% v.w) and the lowest on 28 july (0.29% v.w). totally 55 compounds were identified in the essential oil while the highest percentage belonged to monoterpenes especially the oxygenated ones. most variations were observed in geraniol (1.40-15.34%), geranyl acetate (trace-14.41%) and neryl acetate (0.62-17.51%). the major value in most cases belonged to geranial. conclusion: the results of this study indicate that the harvesting time of plant is an effective factor in the quality and quantity of theessential oil of dracocephalum kotschyi.