Seasonal variation in uterotonic activity of Rhoicissus tridentata extracts.

BACKGROUND: Rhoicissus tridentata lignotubers are widely used in southern African traditional pregnancy-related remedies. OBJECTIVES: To determine the seasonal variation in contractile activity of extracts from different parts of the plant. METHODS: Isolated rat uterus tissue was used to compare the contractile activity of crude aqueous extracts of R. tridentata made from plant material harvested every 3 months over a period of 2 years. RESULTS AND CONCLUSIONS: The activity of the plant extracts from plants harvested in summer and autumn were 4-5-fold higher than extracts from plants harvested in winter or spring. The tubers stimulated the greatest degree of contractions, followed by the stems, roots and leaves. These results highlight the need to standardise the timing of harvesting R. tridentata.

The pharmacological action of Rhoicissus tridentata on isolated rat uterus and ileum.

Decoctions and infusions of Rhoicissus tridentata subsp cuneifolia (Vitaceae) roots and lignotubers are widely used in South African traditional herbal remedies during pregnancy. The pharmacological action of an aqueous extract of R. tridentata subsp cuneifolia roots was investigated using isolated rat uterus and ileum. The extract directly stimulated concentration dependent contractions of the uterus and ileum. Pretreatment with the muscarinic antagonist atropine (40 nM) and the cyclooxygenase inhibitor indomethacin (5 microM) both blocked the contractile response to the Rhoicissus extract suggesting that muscarinic receptors and cyclooxygenase metabolites could be involved in the contractile response to the extract. The serotonergic antagonist methysergide (1 microM) and the alpha-adrenoceptor antagonist prazosin (2 microM) had no effect on the direct action of the extract. This infers that the contractile response to the plant extract is independent of serotonin receptors and alpha-adrenoceptors.