Intestinal myorelaxant and antispasmodic effects of the essential oil of Croton nepetaefolius and its constituents cineole, methyl-eugenol and terpineol

The effects of the essential oil of Croton nepetaefolius (EOCN), a medicinal plant from the north-east of Brazil, and its constituents cineole, methyl-eugenol and terpineol were studied on intestinal motility in vivo and on in vitro mechanical activity of intestinal smooth muscle. In mice, EOCN (10-100 mg/kg body weight, intragastrically) increased the intestinal transit of charcoal marker delivered to the stomach. This was also observed in animals pretreated with castor oil. In segments of guinea-pig ileum and cardial, pyloral and ileo-caecal sphincters, EOCN preferentially decreased basal tonus compared with the amplitude of spontaneous contractions with EC50 values in the range 0.9 - 16 and 8 - 150 mu g/mL respectively. In ileum, EOCN, cineole, methyl-eugenol and terpineol decreased tonus with EC50 values of 16, 322, 9 and 71 mu g/mL, respectively, and blocked 60 mM [K+]-induced contraction with IC50 values of 18, 419, 12 and 95 mu g/mL. The data show that EOCN possesses myorelaxant and antispasmodic properties in vitro, consistent with the use of Croton nepetaefolius in folk medicine as an intestinal antispasmodic, EOCN-induced stimulation of intestinal transit in vivo appears consistent with its in vitro effects, since a preferential decrease in tonus may reduce luminal resistance to bulk Bow of intestinal contents. (C) 1998 John Wiley & Sons, Ltd.