Chemical Synthesis of Deoxynivalenol-3-β-d-[(13)C₆]-glucoside and Application in Stable Isotope Dilution Assays.
Since deoxynivalenol (DON), the main representative of Fusarium toxic secondary metabolites, is a relatively common natural contaminant in barley, its traces can be detected in many commercial beers. Our previous study reporting for the first time the occurrence of relatively high levels of DON-3-glucoside (DON-3-Glc) in malt and beer prepared from relatively "clean" barley (semiscale experimental conditions) induced a follow-up investigation focused on this DON conjugate in commercial beers. The current survey involving in total 176 beers, representing different brands, and collected at various markets, has documented a ubiquitous occurrence of DON-3-Glc in this product. Its levels even exceeded that of free DON in some samples; the highest level found was 37 microg/L. In addition to glucosylated DON, its acetylated forms (ADONs) were also common contaminants in most of the beers. Generally, stronger beers (higher alcohol content) tended to contain higher levels of DON and its conjugates. No distinct relationship between the contamination of malt and beer was observed in samples collected from several breweries. Attention was also paid to comparison of data on malts obtained by LC-MS/MS and ELISA DON-dedicated kits. The latter provided apparently higher levels of DON, the most distinct difference being observed for malts processed at higher temperatures (caramel and roasted malts). The nature of this phenomenon has not yet been explained; in addition to cross-reacting species, other factors, such as the higher content of dark pigment, can also be the cause.