The leaves of Ageratina cylindrica afforded a thymol derivative that was characterized by physical and
spectroscopical methods as (8S)-8,9-epoxy-6-hydroxy-l0-benzoyloxy-7-oxothymol isobutyrate (1). The absolute configuration of
1 was established as 8S by vibrational circular dichroism spectroscopy in combination with density functional theory calculations
and by evaluation of the Flack and Hooft X-ray parameters. Compound 1 showed weak antiprotozoal activity against Entamoeba
histolytica and Giardia lamblia trophozoites and a high inhibitory effect on hyperpropulsive movement of the small intestine in
rats.