Quantification of Phorbol Esters in Jatropha curcas by HPLC-UV and HPLC-ToF-MS with Standard Addition Method

Abstract

Established analytic methods for the quantification of phorbol esters (PE), which are some toxic components in Jatropha curcas L., include HPLC with UV-detection with the commercially available phorbol myristate acetate (PMA) as internal standard or HPLC coupled with MS detection with an external calibration, mostly also with PMA. The differences in the fatty acid side chains and connection to the base structure of PMA compared to PE leads to different UV absorption and MS ionization effects and cause problems for exact quantitative measurements. In this paper, a method is presented which combines both detection types and shows differences between both results. For this purpose, an extraction routine is performed on a PE-containing seed oil to get a PE standard in high purity, which was used for a standard addition method on two real J. curcas oil samples, derived from Ghana and Mexico. Furthermore, a detection window of ≈10 ppm for the high accurate ToF-MS detection is set to eliminate isobaric interferences from co-eluting material. Method evaluation of inter-and intra-day variance as well as the recovery rate are performed and determined. With this method a limit of detection of 62 ng mL1 (UV) and 11 ng mL1 (MS) can be achieved. Practical Applications: Due to the good biological and technical properties of Jatropha curcas L., its seed oil seems perfect for the application as biodiesel feedstock. The toxicity on the other hand could cause problems when converting side products from the oil production to products of higher value. With the here described method an accurate and precise analysis procedure for the quantification of the toxic compounds namely, phorbol esters, could be applied for toxicity studies or routine checks in industry which is converting plant material from J. curcas, so that no toxic material is used for example as animal feed.