Toxicology and pharmacology of sodium ricinoleate

Abstract

Ricinoleic acid constitutes approximately 90% of the fatty acid content of castor oil. Castor oil is known for its purgative effects and can be used to induce labor. Both castor oil and ricinoleic acid are approved for use in food. The mechanistic basis for purgative actions likely includes the membrane-disruptive effects of detergent-like molecules, such as sodium ricinoleate (a ‘soap’). These effects have been shown to be dose-related and to exhibit a threshold below which no laxative response was evident, in both animals and in humans. Castor oil was not toxic in subchronic feeding studies in rodents at doses ranging up to 10–20% of the diet. Sodium ricinoleate, as a surfactant, demonstrates predictable skin and mucus membrane irritant effects, and may induce a Type IV dermal sensitization response in those previously sensitized to it. However, food-grade castor oil and sodium ricinoleate are prepared in such a manner as to be free of the castor bean constituents that have been proven to be the source of reported Type I immediate hypersensitivity responses. Feeding studies with castor oil in rodents provide a basis for a no observable adverse effect level (NOAEL) estimate of 7500 mg/kg/day and 5000 mg/kg/day in mice and rats, respectively ( NTP, 1992). Applying an uncertainty factor of 100 to the lesser of these NOAELs, one can thus estimate an acceptable daily intake (ADI) in man to be 50 mg/kg, or 3000 mg of castor oil per day in an average 60 kg person. As ricinoleic acid constitutes approximately 90% of castor oil, applying this calculation to the 3000 mg/day estimated ADI in humans for castor oil (given the rapid hydrolysis of castor oil glyceride in the gastrointestinal tract), the acceptable daily intake of ricinoleic acid may be as high as 2400 mg/person.