Abstract: The volatile components in essential oils of Conyza canadensis fresh flowers and fresh achenes extracted by steam distillation were analyzed by GC-MS. The results show that essential oils contained five compounds, including two kinds of hydrocarbons, two kinds of alcohols, one kind of ketone at above 96% of match quality. The volatiles contained four perfumes which were cis-2-methyl-5-(1-methylethenyl)-2-cyclohexen-1-ol (carveol), trans-2-methyl-5-(1-methylethenyl)-2-cyclohexen-1-ol (trans-carveol), and (s)-2-methyl-5-(1-methylethenyl)-2-cyclohexen-1-one(s-carvone).They also contained 2,6-dimethyl-6-(4-methyl-3-pentenyl)-bicyclohept-2-ene. The essential oil of C. canadensis fresh flowers and fresh achenes have potential values on perfume and herbicide because of terpenoids and alkyl ketones with allelopathy.

Key words: Conyza canadensis, fresh flower, fresh achene, essential oil, GC-MS