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Quantification of the Emetic Toxin Cereulide in Food Products by Liquid Chromatography-Mass Spectrometry Using Synthetic Cereulide as a Standard

Biesta-Peters, Elisabeth G., Reij, Martine W., Blaauw, Richard H., in 't Veld, Paul H., Rajkovic, Andreja, Ehling-Schulz, Monika, Abee, Tjakko
Applied and environmental microbiology 2010 v.76 no.22 pp. 7466-7472
Bacillus cereus, bioactive properties, boars, eukaryotic cells, foods, mass spectrometry, membrane potential, mitochondria, potassium, solutes, sperm motility, toxins, valinomycin
Bacillus cereus produces the emetic toxin cereulide, a cyclic dodecadepsipeptide that can act as a K⁺ ionophore, dissipating the transmembrane potential in mitochondria of eukaryotic cells. Because pure cereulide has not been commercially available, cereulide content in food samples has been expressed in valinomycin equivalents, a highly similar cyclic potassium ionophore that is commercially available. This research tested the biological activity of synthetic cereulide and validated its use as a standard in the quantification of cereulide contents in food samples. The synthesis route consists of 10 steps that result in a high yield of synthetic cereulide that showed biological activity in the HEp-2 cell assay and the boar sperm motility assay. The activity is different in both methods, which may be attributed to differences in K⁺ content of the test media used. Using cereulide or valinomycin as a standard to quantify cereulide based on liquid chromatography-mass spectrometry (LC-MS), the concentration determined with cereulide as a standard was on average 89.9% of the concentration determined using valinomycin as a standard. The recovery experiments using cereulide-spiked food products and acetonitrile as extraction solute showed that the LC-MS method with cereulide as a standard is a reliable and accurate method to quantify cereulide in food, because the recovery rate was close to 100% over a wide concentration range.