Masked Mycotoxins:  Determination of a Deoxynivalenol Glucoside in Artificially and Naturally Contaminated Wheat by Liquid Chromatography−Tandem Mass Spectrometry

Abstract

Conjugated mycotoxins, in which the toxin is usually bound to a more polar substance like glucose, are referred to as masked mycotoxins, as these substances escape routine detection methods but can release their toxic precursors after hydrolysis. This is the first report on the natural occurrence of a glucoside of deoxynivalenol (DON) in Fusarium-infected wheat and maize. To obtain appropriate standards, we chemically synthesized deoxynivalenol-3-beta-D-glucopyranoside (DON-3-glucoside) and deoxynivalenol-15-beta-D-glucopyranoside (DON-15-glucoside). The synthesis products were characterized by liquid chromatography-tandem mass spectrometry. The DON-glucosides showed different collision-induced dissociation (CID) fragmentation behaviors and could therefore be distinguished. Wheat plants were either treated with DON (n = 52) or with Fusarium spp. (n = 4) at anthesis, and after harvest, wheat ears were analyzed for DON and DON-glucosides. All 56 treated wheat samples contained DON and a DON-glucoside with the same retention time, molecular mass, and CID fragmentation behavior as the synthetic DON-3-glucoside. Moreover, the DON-glucoside was also found in two out of three analyzed naturally DON-contaminated maize and in five out of five naturally contaminated wheat samples, in a range from 4 to 12% of the DON concentration. To further confirm the identity of the DON-glucoside, the compound was isolated from wheat extracts and characterized as DON-3-glucoside with NMR. The results of this study indicate the importance to consider both DON and DON-3-glucoside with regard to food and feed safety.

Occurrence of free and conjugatedFusariummycotoxins in cereal-based food

“…Metabolism by the host plant generally aims at detoxification of these compounds which is often accomplished by attachment of hydrophilic groups, thus increasing their solubility in water (Engelhardt et al 1999;Karlovsky 1999). In this manner, DON is converted to DON-3-glucopyranoside (D3G) (Sewald et al 1992;Berthiller et al 2005), and ZON can be altered to ZON-4 glucopyranoside (Z4G) (Engelhardt et al 1988) by plants.…”

Changes in the content of various Fusarium mycotoxins forms in germinating winter wheat and spring barley kernels

“…Maul et al (2012) determined 30% reduction of DON in steeping process. Berthiller et al (2005) detected 1:3 ratio of D3G to DON in wheat kernels. From our results, it was concluded that the ratio could be higher in harvested kernels, even 1:1 (Figure 2a, barley).…”

“…Conjugated forms arise from DON as detoxification products decreasing toxicity of DON in plants (Berthiller et al 2005) or they are intermediate products on DON biosynthetic pathway in Fusarium (McCormick et al 2011), as in case of ADONs. It is evident that testing of primary produced DON in plants is insufficient for evaluation of total content of Fusarium mycotoxins, both in non-processed raw material and processed products.…”

Mycotoxins in Wheat and Mitigation Measures

“…Modified mycotoxins represent another emerging topic. Plant metabolites have been identified so far for DON, NIV, fusarenon-X, T-2 toxin, HT-2 toxin, ZEA, ochratoxin A (OTA), destruxins, fusaric acid, and modified fumonisins have been found, especially in wheat and other cereal commodities [41][42][43][44][45][46]. The acetylated derivatives of DON, 3-ADON, and 15-ADON are frequently detected in DON-contaminated grains [47].…”