The molecular mechanism of the active ingredient in castor oil, used for many centuries as a laxative and labor-inducer, has been found.

“There were many theories as to how castor oil worked, including broad toxicity to intestine cells and effects on water and electrolytes,” said Stefan Offermanns, a biologist at the Max Planck Institute for Heart and Lung Research in Germany and lead author of the present study.

Instead, the researchers found that it is ricinoleic acid’s specificity to bind to particular receptor in the intestines and uterus that causes the laxative (and labor in pregnant women) effect associated with castor oil.

Ricinoleic acid is a fatty acid and makes up about 90 percent of the castor oil.

Study was conducted on animal models. It was found that ricinoleic acid works by attaching itself to EP3 receptor.

“We show that the active component of castor oil, ricinoleic acid, is a selective agonist of EP3and EP4 receptors, and that the pharmacological effects of castor oil are mediated by activation of EP3 receptors on smooth-muscle cells,” write Stefan Offermanns and colleagues.  

 “When you study classic, old drugs, you almost always learn something from them. The major surprise here was how specifically castor oil worked,” said Offermanns.

“They did these experiments quite elegantly and comprehensively and at one level, this finding is sort of a quaint little curiosity, but there’s more to it than that,” said Phillip Bennett, biologist at Imperial College London.

Castor Oil has been used as a laxative for some 3,500 years. Alternative medicine or folk remedies still recommend use of castor oil.

U.S. FDA categorizes castor oil as safe and effective, according to Nature.

According to a related study, women given castor oil have increased chances of initiation of labor within 24 hours than women who are not given castor oil. Researchers of related studies say that use of castor oil to induce labor is an economical and safe in uncomplicated pre-mature rupture of membranes

The study is published in the Proceedings of the National Academy of Sciences.