In vitro determination of the uterine stimulatory effect of the aqueous leaf extract of Ficus exasperata

Ethnopharmacological relevance: The leaves of Ficus exasperata Vahl (Moraceae) are used by traditional healers in Southern Nigeria to arrest pre-term contractions and are also used as an abortifacient in some parts of Africa. Aim of study: An earlier study on the aqueous leaf extract of Ficus exasperata (AET) showed that the extract at lower concentrations inhibited oxytocin-induced uterine contractions and at higher concentrations, stimulated uterine contraction. This study thus aims to determine, the possible mechanisms by which AET stimulates uterine contraction in vitro. Materials and methods: The contractile effect of AET (5.0 × 10-2 to 100 × 10-2 mg/ml) and oxytocin (which was used as a reference drug) were examined in the presence of the following antagonists: atropine (1.18 and 11.91 nM); indomethacin (1.42 and 14.25 nM); verapamil (2.03 and 20.35 nM); phentolamine (4.09 and 40.91 nM), or diphenhydramine (4.45 and 44.47 nM). The EC50 and Emax were determined and statistically analyzed using one-way ANOVA and Dunnett post hoc test. Results: There was no significant difference in the EC50 and Emax of AET and oxytocin in the presence of atropine. Diphenhydramine and phentolamine significantly inhibited (p < 0.01) the extract but both drugs had no effect on oxytocin. However, significant differences (p < 0.01) were observed in the EC50 and Emax of AET and oxytocin in the presence of verapamil and indomethacin. Conclusions: These results suggest that the stimulation of uterine contractility by AET may arise from the activation of histamine H1- and/or α-adrenergic receptors, interference with calcium channels and/or stimulation of prostaglandin synthesis in utero. © 2009 Elsevier Ireland Ltd. All rights reserved.