OXYTOCIN-LIKE EFFECT OF HARPAGOPHYTUM PROCUMBENS DC [PEDALIACEAE] SECONDARY ROOT AQUEOUS EXTRACT ON RAT ISOLATED UTERUS

Abstract

Harpagophytum procumbens DC [family: Pedaliaceae] is widely used in South African traditional medicine for the treatment, management and/or control of a variety of human ailments. Some traditional health practitioners of South Africa have claimed that H. procumbens secondary root is a useful obstetric remedy for induction or acceleration of labour, as well as for expulsion of retained placentas in pregnant women. In the present study, we have, therefore, examined the effects of Harpagophytum procumbens secondary root aqueous extract (HPE) on isolated uterine muscle strips taken from pregnant and non-pregnant, young female rats. The plant’s extract (HPE, 10–800 g/ml) induced concentration-related, significant (P<0.05–0.001) increases in the baseline tone (basal tension), and caused powerful spontaneous, rhythmic, myogenic contractions of the oestrogen-dominated uterine muscle strips taken from stilboesterol-pretreated, non-pregnant female rats. Relatively low to high concentrations of H. procumbens secondary root aqueous extract (HPE, 10–800 g/ml) also provoked concentration-dependent, significant (P<0.05–0.001) increases in the baseline tone (basal tension) and contracted uterine muscle strips taken from female rats in the early, middle and late stages of pregnancy. Moderate to high concentrations of the plant’s extract (HPE, 200–1000 g/ml) always provoked powerful contractions of isolated uterine muscle preparations of non-pregnant and pregnant rats. The results of this in vitro study indicate that H. procumbens secondary root aqueous extract (HPE) possesses significant contractile effect and/or uterotonic action on mammalian uterus. This finding probably suggests that the use of Harpagophytum procumbens secondary root preparations should be contra-indicated in pregnancy. The contractile effect and/or uterotonic action of the plant’s extract may be due to release of uterotonic substances or mediators. However, the findings of the present laboratory animal study lend pharmacological credence to the suggested folkloric, obstetric uses of the plant’s secondary root for induction or acceleration of labour, as well as for expulsion of retained placentas in pregnant women in some communities of Southern Africa.