People have long taken castor oil to help ease constipation and induce labor, but until now, little was known about how the pressed oil of the castor bean actually works. Now, scientists have found that ricinoleic acid, a key component of castor oil, targets prostaglandin receptors on smooth muscle cells in the intestines and uterus to stimulate contractions, according to research published today (May 21) in Proceedings of the National Academy of Sciences.
Researchers in Germany identified EP3, a receptor for prostaglandin E2, a hormone-like molecule that mediates a range of functions, including labor and temperature control, after screening human cell lines for responses to ricinoleic acid. Although ricinoleic acid administered to normal mice produced diarrhea, mice lacking EP3 showed no ill effects from ricinoleic acid ingestion. Ricinoleic acid also stimulated uterine contractions in pregnant wild type uterine tissue, but not in uteri from EP3-deficient mice.
Castor oil’s specific mechanism of action is “unexpected because castor oil has been regarded as an agent that exerts its effects through unspecific mechanisms,” the authors noted, but the data identify EP3 receptors as “potential targets for drugs to induce laxation.”
Read more about the science behind different alternative medicines, including probiotics, acupuncture, and medical marijuana, in The Scientist’s July issue.