Degradation rates of phorbol esters in Jatropha curcas L. oil and pressed seeds under different storage conditions

BACKGROUND: Phorbol esters (PEs), found in Jatropha curcas crude oil (JCO) and J. curcas pressed seeds (JPS), are known as bioactive compounds in agricultural and pharmaceutical applications. The degradation rates of PEs in JCO and JPS under various conditions is important for the utilisation of PEs. Thus the objective of this study was to determine the PE degradation rates in JCO and JPS under different storage conditions. RESULTS: PE degradation rates were found to be first-order reactions. The slowest degradation rate was at 0.9 × 10⁻³ d⁻¹ for both JCO and JPS unexposed to light at 4 °C. Light intensity (1097 lx and 4690 lx, representing diffused sunlight and fluorescent lighting, respectively) and temperature (25 to 35 °C) were the significant degradation factors. Light exposure led to 280% to 380% higher degradation rates in JCO than in JPS due to light penetration through the transparent oil. Dried and sterilised JPS showed an 80% to 90% lower PE degradation rate than untreated JPS under all storage conditions since biodegradation was assembly limited. CONCLUSION: The PEs were unstable under the studied conditions, especially when exposed to light and room temperature. To protect against PE degradation, a material should be stored in a light-protected container and below 4 °C.