Cytotoxicity, acute toxicity, and general pharmacological effects in mice of an arylnaphthalene lignan isolated from Jisticia hyssopifolia were studied. Elenoside was cytotoxic to human cancer cell lines in a range of concentrations from 10(-5) to 10(-4)M. It has an LD(50), ip in mice, of 305 mg/kg and central depressive properties at doses of 25, 50, and 100 mg/kg. Thus, elenoside appears to be a sedative with broad spectrum cytotoxicity.