SELECTIVE MODULATORY EFFECTS OF THE ESSENTIAL OIL OF CROTON ZEHNTNERION ISOLATED SMOOTH-MUSCLE PREPARATIONS OF THE GUINEA-PIG

The effects of the essential oil of the plant Croton zehntneri (EOCz) in the concentration range 1-200 mu g/mL were studied on the mechanica l activity of various in vitro smooth muscle preparations of the guine apig. In isolated ileum EOCz induced a variable response such that in 57% of tissues basal tone was reduced (EC50 5 mu g/mL) whereas the res t remained unaffected by the oil. In concentrations above 10 mu g/mL E OCz induced spontaneous oscillatory contractions in all preparations. In contrast the basal tone of the aorta, portal vein and bladder remai ned unaltered by the oil. In the portal vein EOCz concentration-depend ently inhibited the amplitude of spontaneous contractions (IC50 109 mu g/mL) without reducing frequency, whereas in the bladder such activit y was increased by the oil (EC50 44 mu g/mL). In ileum precontracted w ith 60 mM KCI, EOCz induced a complete and concentration-dependent rel axation with an IC50 value of approximately 26 mu g/mL. In contrast EO Cz did not relax KCI-induced tone in the aorta or bladder, whilst elic iting less than 20% relaxation of the precontracted portal vein, Thus our data show that EOCz exerts differential modulatory effects on the contractility of various smooth muscles of the guinea-pig. That EOCz a ppears to selectively relax intestinal smooth muscle may support its u se in folk medicine as a gastrointestinal antispasmodic. (C) 1998 John Wiley & Sons, Ltd.