Aqueous extracts of castor seed (Ricinus communis) increase the contractile activities of mouse uterine tissues in vivo

Administration of castor oil from seeds of Ricinus communis is a commonly cited herbal preparation used to induce labor. The ricinoleic acid found in castor oil is more polar than most fats and activates uterine EP3 prostanoid receptors. The purpose of this study was to determine if an aqueous extract from the castor seed would also demonstrate uterotonic behaviors, implicating ricinoleic acid’s solubility in water. Aqueous extracts of castor seed were tested on isolated mouse uterine tissues in an organ bath. Increases in uterine contractile forces were observed, and at higher concentrations were greater than those produced by acetylcholine and similar to those from oxytocin. Results suggest that ricinoleic acid is present in aqueous extracts. Attempts to characterize uterine contractile responses were done with the understanding that the extract may contain a number of active constituents whose contributions may be synergistic, additive, or antagonistic to the overall tissue contractile response.