Development of a stable isotope dilution analysis for the quantification of the Bacillus cereus toxin cereulide in foods.
An increasing number of severe food borne intoxications are caused by a highly stable depsipeptide, named cereulide, which is produced by emetic Bacillus cereus strains. As cereulide poses a health risk to humans, the development of an appropriate method for the analysis of this toxin is mandatory. Therefore, the reference material of cereulide as well as its (13)C(6)-isotopologue was prepared by means of a biosynthetic approach using a B. cereus culture, followed by a rapid but efficient downstream purification. After structure confirmation by means of liquid chromatography (LC)-time-of-flight mass spectrometry, LC-tandem mass spectrometry, and one-/two-dimensional NMR spectroscopy, a stable isotope dilution analysis (SIDA) was developed for the quantification of cereulide in foods using the (13)C(6)-cereulide as the internal standard. Validation experiments were performed, and the data were compared to the quantitative analysis using the structurally related valinomycin instead of the (13)C(6)-cereulide as an internal standard. Trueness, repeatability, and reproducibility expressed as relative standard deviation showed values <10 or <8% for valinomycin or <8% for (13)C(6)-cereulide, respectively. Furthermore, the MS response of the valinomycin was found to be significantly influenced by the food matrix, thus leading to rather low recovery rates of 91% from boiled rice and 80% from boiled rice supplemented with 10% sunflower oil. In comparison, the use of (13)C(6)-cereulide as an internal standard gave good recovery rates of 104 and 111% from both matrices, thus demonstrating the robustness and accuracy of the developed SIDA.
Bauer
Tobias
T
Microbiology Unit, ZIEL Nutrition and Food Research Center, WZW, Technische Universitat Munchen, 85354 Freising, Germany.
Stark
Timo
T
Hofmann
Thomas
T
Ehling-Schulz
Monika
M
D001409:Bacillus cereus / Q000737:chemistry* / Q000378:metabolism; D001427:Bacterial Toxins / Q000032:analysis* / Q000378:metabolism; D002247:Carbon Isotopes / Q000032:analysis* / Q000378:metabolism; D047630:Depsipeptides / Q000032:analysis* / Q000378:metabolism; D005506:Food Contamination / Q000032:analysis*; D007553:Isotope Labeling / Q000379:methods*
D001427:Bacterial Toxins; D002247:Carbon Isotopes; D047630:Depsipeptides; C089294:cereulide