This paper deals with the effects of elenoside, (3-hidroxymethyl-1-methoxy-5,6-methylene-dioxy-4-(3,4-methylenedioxyphenyl)-2-naftoic acid lactone-β-D-glucoside) an arylnaphthalene lignan with broad spectrum cytotoxicity in a human tumor cell line panel, isolated from Justicia hyssopifolia (Acanthaceae) grown in the Canary Islands (Spain), on isolated cardiac auricle of rabbits, urinary excretion of rats, and on isolated rat ileum. These effects, using a vehicle (propylene glycol–ethanol–plant oil–Tween 80 (40 : 10 : 50 : 2) as a standard, are presented. Elenoside at concentrations of 3.2×10⁻⁴, 6.4×10⁻⁴, and 1.2×10⁻³ M produced an increase in the contraction force of auricles in a concentration-dependent way. At doses of 25 and 50 mg/kg, an antidiuretic effect and a decrease in sodium excretion were observed. Elenoside at concentrations of 3.2×10⁻⁴, 6.4×10⁻⁴ and 1.2×10⁻³ M produced an increase in the contraction force of ileum in a concentration-dependent manner. Elenoside produced the concentration dependent inhibition of ⁸⁶Rb uptake. These results indicate that elenoside has digitalis-like activity similar to mammalian lignans. Moreover, this lignan has an irritant effect on the gastrointestinal tract.