diurnal variation of essential of the oil components of pycnocycla spinosa decne. ex boiss

background pycnocycla spinosa decne. ex boiss is an aromatic plant which showed relaxant effects on isolated ileum contractions and antidiarrheal activity. thirty four components have been extracted from p. spinosa essential oil, of which several major constituents were found to show seasonal variation. objectives the aim of this work is to evaluate the diurnal variation of its oil constituents during specific hours of the day. materials and methods the pycnocycla spinosa samples were collected at different times of the day. the hydro-distilled aerial parts oils of collected p. spinosa were analyzed by gc and gc/ms. results fourteen monoterpenoid and nine sesquiterpenoid components were identified, of which the fluctuating constituents were p-cymene, trans-β-ocimene, β-citronellol, citronellyl pentanoate, geranyl isovalerate, α-humulene, caryophyllen oxide, α-cadinol, and α-eudesmol. the content of p-cymene in the essential oil in different daily times varied from 0.16 to 4.19%, and the geranyl isovalerate 7.75 -23.99%. conclusions essential oils with different qualities can be obtained according to the harvest time of the plant in a day.