Uterotonic effect of Harpagophytum procumbens DC (Pedaliaceae) secondary root aqueous extract on rat isolated uterine horns.

Some traditional health practitioners of South Africa have claimed that Harpagophytum procumbens DC (family: Pedaliaceae) secondary root is a useful obstetric remedy for induction or acceleration of labour, as well as for expelling retained placentas in pregnant women. In the present study, therefore, we investigated the effect of H. procumbens secondary root aqueous extract (HPE) on longitudinal, tubular uterine horn muscle strips taken from non-pregnant and pregnant, young adult, female rats. HPE (10-800 microg/ml) induced concentration-related and significant (P<0.05) increases in the baseline tone, and caused powerful rhythmic, myogenic contractions of, oestrogen-dominated rat longitudinal uterine horn muscle strips taken from stilboesterol-pretreated, non-pregnant female rats. Relatively low to high concentrations of HPE (10-800 microg/ml) also provoked concentration-dependent and significant (P<0.05-0.001) increases in the baseline tone of, and contracted, longitudinal, tubular uterine horn muscle strips taken from female rats in the early, middle and late stages of pregnancy. Moderate to high concentrations of HPE (200-1,000 microg/ml) always provoked powerful contractions of isolated longitudinal, tubular uterine horn muscle preparations of non-pregnant and pregnant rats. The results of this in vitro study indicate that H. procumbens secondary root aqueous extract possesses spasmogenic, uterotonic action on mammalian uterine muscles. These findings lend pharmacological credence to the suggested folkloric obstetric uses of the plant's secondary root for induction and/or acceleration of labour, as well as for expelling retained placentas in pregnant women.