The possible mechanisms for the antifertility action of methanolic root extract of Rumex steudelii

Background: The practice of traditional medicine for the control of fertility in most parts of Ethiopia is based on the uses of plant medicines for many years. Rumex steudelii Hochst (Polygonaceae) , locally known as "Tult" or "Yeberemelas" is one of the traditionally used antifertility plants in Ethiopia. In our previous study, the methanolic extract of R. steudelii root was found to show antifertility activity in female rats. Objectives: The present study focused further on the possible mechanisms of the antifertility effect of the methanolic extract of R. steudelii. Methods: The effect of the extract on implantation, the uterus weight of immature ovariectomized rats and serum estrogenprogesterone ratio was evaluated. Its effect on isolated guinea pig uterus in the presence and absence of uterine muscle contractions inhibitors was also assessed. Test for in vivo abortifacient effect was also carried out. Results: It was found that the extract decreased the number of implantation sites significantly. At a contraceptive dose, it was also observed to have no estrogenic activity in immature rat bioassay. The extract did not affect the serum estrogen-progesterone ratio. It produced concentration dependent increase in uterine muscle contractions similar to those of the standard drug, oxytocin. Incubation of the tissue with three uterine muscle contractions inhibitors revealed that the extract produced uterine contractions perhaps by activating muscarinic and/or histaminic receptors. The in vivo abortifacient effect was not seen upon administration of both lower and higher doses of the extract in pregnant rats. Conclusion: All these observations suggest that the extract produced antifertility effect mainly by inhibiting implantation though antiestrogen, progesterogen and uterotonic effects could as well be possible mechanisms