Toxin Repertoire: Diversity of (Iso)cereulide(s).

The emetic toxin cereulide () poses a significant safety risk in the food industry, causing emesis and nausea after consumption of contaminated foods. Analogously to cereulide, the structures of various isocereulides, namely, isocereulides A-G, have been recently reported and could also be identified in -contaminated food samples. The HPLC fractionation of extracts allows us to isolate additional isocereulides. By applying MS sequencing, post-hydrolytic dipeptide, amino acid and α-hydroxy acid analyses using UPLC-ESI-TOF-MS to purify the analytes, seven new isocereulides H-N (-) could be elucidated in their chemical structures. The structure elucidation was supported by one-dimensional and two-dimensional NMR spectra of the isocereulides H (), K (), L and N ( + ) and M (). The toxicity of - was investigated in a HEp-2 cell assay to determine their respective 50% effective concentration (EC). Thus, - exhibited EC values ranging from a 0.4- to 1.4-fold value compared to cereulide (). Missing structure-activity correlations indicate the necessity to determine the toxic potential of all naturally present isocereulides as single compounds to be able to perform a thorough toxicity evaluation of -contaminated foods in the future.