The essential oils isolated from the leaves of Ageratum houstonianum Mill. and Ageratum conyzoides L. by hydrodistillation were analysed by GLC and GC-MS. The essential oil of A . houstonianum contained 7-methoxy-2.2-dimethylchromene (precocene I) and ageratochromene (precocene 11) in almost similar amounts (32% and 24% respectively) whereas that of A. conyzoides was rich in precocene I (81%) and poor in precocene I1 (0.2%). Our findings are compared with those of the literature.

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