In vitro myometrial inhibition by the partitioned aqueous fraction of Anthocleista djalonensis leaves

This study investigated the effect on the uterus of the aqueous fraction of the partitioned methanol crude extract of the leaves of Anthocleista djalonensis (AD) and the possible mechanism of AD activity. AD inhibited the concentration-response curves induced by oxytocin and CaCl2 on the rat uterus in vitro and significantly reduced the EC50 in a concentration-dependent manner (p?< 0.05). A similar effect was observed with salbutamol and verapamil on the concentration-response curves obtained for oxytocin and CaCl2. The inhibitory effect of AD was not attenuated in the presence of propranolol. AD, salbutamol, and verapamil also produced a concentration-dependent relaxation on K+-induced sustained uterine contraction. In Ca2+-free medium, AD and salbutamol similarly inhibited oxytocin-induced contraction, but verapamil failed to produce this effect. The present results suggest that AD, being a mixture of phytochemicals, probably exerts inhibitory activity on in vitro uterine contractions of the nonpregnant, diethylstilboestrol-treated rat by multiple mechanisms that do not involve interaction with β-adrenergic receptors and do not solely depend on inhibition of calcium influx.