Structure, Absolute Configuration, and Antidiarrheal Activity of a Thymol Derivative from <i>Ageratina cylindrica</i>

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