title: Biosynthesis of seven carbon-13 labeled Alternaria toxins including altertoxins, alternariol, and alternariol methyl ether, and their application to a multiple stable isotope dilution assay.
abstract: An unprecedented stable isotope dilution assay for the genotoxic altertoxins along with exposure data of consumers is presented to enable a first risk assessment of these Alternaria toxins in foods. Altertoxins were produced as the most abundant Alternaria toxins in a modified Czapek-Dox medium with a low level of glucose as the carbon source and ammonium sulfate as the sole nitrogen source. Labeled altertoxins were synthesized in the same way using [(13)C6]glucose. Moreover, labeled alternariol, alternariol methyl ether, altenuene, and alternuisol were biosynthesized in another modified medium containing [(13)C6]glucose and sodium [(13)C2]acetate. A stable isotope dilution LC-MS/MS method was developed and used for food analysis. For altertoxin I, altertoxin II, alterperylenol, alternariol, and alternariol methyl ether, the limits of detection ranged from 0.09 to 0.53 μg kg(-1). The inter-/intra-day (n = 3 × 6) relative standard deviations of the method were below 13%, and the recoveries ranged between 96 and 109%. Among the various commercial food samples, some of the organic whole grains revealed low-level contamination with altertoxin I and alterperylenol, and paprika powder, which was heavily loaded with alternariol, alternariol methyl ether, and tentoxin, showed higher contamination level of altertoxin I and alterperylenol. Altertoxin II and III and stemphyltoxin III were not detectable. In addition, if the food was contaminated with altertoxins, it was likely to be co-contaminated with the other Alternaria toxins, but not necessarily vice versa. Maximum concentrations of altertoxin I and alterperylenol were detected in sorghum feed samples containing 43 and 58 μg kg(-1), respectively. This was significantly higher than that in the measured food samples.
authors.affiliation: Chair of Analytical Food Chemistry, Technische Universität München, Alte Akademie 10, 85354, Freising, Germany.
authors.forename: Yang
authors.initials: Y
authors.lastname: Liu
authors.forename: Michael
authors.initials: M
authors.lastname: Rychlik
mesh_terms: D000528:Alternaria / Q000378:metabolism*; D000821:Animal Feed / Q000032:analysis*; D002247:Carbon Isotopes / Q000032:analysis; D005506:Food Contamination / Q000032:analysis; D007201:Indicator Dilution Techniques; D009183:Mycotoxins / Q000096:biosynthesis* / Q000737:chemistry
chemical_list: D002247:Carbon Isotopes; D009183:Mycotoxins