Ricinine, a toxic compound found in castor plants (Ricinus communis), causes abdominal pain, nausea, and vomiting. Castor leaves and castor oil-based dietary supplements are commonly consumed, but their ricinine content has not been evaluated for safety. This study aimed to determine the ricinine concentration in these products and to evaluate the ricinine exposure level from their consumption. The developed method combines the Quick, Easy, Cheap, Effective, Rugged, and Safe (QuEChERS) technique and liquid chromatography–tandem mass spectrometry (LC–MS/MS). A matrix-matched calibration method for castor leaves is then proposed, which demonstrates high linearity over a wide concentration range (50–1000 µg/kg; r2 > 0.995). The intraday and interday accuracies ranged from 93.6% to 113.7%; the precisions were within 10%. The limits of detection and quantitation were ≤ 8.9 µg/kg and ≤ 26.9 µg/kg, respectively, and this validated method was successfully applied to commercial castor plant-based products. Ricinine exposure from the consumption of these foods was estimated to be 0.0001–0.2792 µg/kg body weight/day. This study assesses the safety of castor plant-based food products and could help prevent potential health risks associated with ricinine consumption.
