Synthesis of four carbon-13-labeled type A trichothecene mycotoxins and their application as internal standards in stable isotope dilution assays

The first stable isotope dilution assay (SIDA) for the simultaneous quantitation of the most abundant type A trichothecenes in foods and feeds was developed. Synthesis of carbon-13-labeled T2-toxin, HT2-toxin, diacetoxyscirpenol, and monoacetoxyscirpenol was accomplished by [C-13(2)]-acetylation of T2-triol and scirpentriol, respectively. Scirpentriol was prepared from diacetoxyscirpenol by complete alkaline hydrolysis and subsequently was converted to [C-13(6)]-triacetoxyscirpentriol by peracetylation with [C-13(4)]-acetic anhydride. The latter compound was selectively hydrolyzed using ammonium hydroxide to give [C-13(4)]- diacetoxyscirpenol and [C-13(2)]- monoacetoxyscirpenol in reasonable yields. Analogously, [C-13(6)]-T2-triacetate was prepared from T2-triol and subjected to controlled hydrolysis to yield [C-13(4)]-T2-toxin and [C-13(2)]-HT2-toxin. All synthesized products were characterized by NMR and MS experiments. Using the prepared isotopically labeled standards, SIDAs were developed for the quantitation of type A trichothecenes in food and feeds. The mycotoxins were quantified by LC-single and tandem MS after cleanup on multifunctional columns. The method revealed good sensitivity with low detection and quantification limits along with excellent recovery and good precision in interassay studies. Food samples were analyzed using the developed SIDA and showed substantial contamination of oat products with T2-toxin and HT2-toxin. Diacetoxyscirpenol was detected on potatoes, whereas monoacetoxyscirpenol was not present in the analyzed samples.