Preparation And Characterization Of The Conjugated Fusarium Mycotoxinszearalenone-40-β-d-glucopyranoside, α-zearalenol-40-β-d-glucopyranosidernand β-zearalenol-40-β-d-giucopyranoside By Ms/ms And Two-dimensional Nmr

摘要

Glucosides of several Fusarium mycotoxins occur in naturally infected cereals and may contribute to an increased content to the total mycotoxin load of food and feed. The paper presents the results of a fermentation procedure to produce zearalenone-4O-β-D-glucopyranoside from zearalenone using an engineered Saccharomyces cerevisiae strain, expressing the Arabidopsis thaliana UDP-glucosyltransferase UGT73C6. About 24mg of zearalenone-4O-β-D-glucopyranoside was obtained from 50 mg of zearalenone and further purified. A total of l0mg of the glucoside were reduced with sodium borohydride, yielding 4.1 mg a-zearalenol-4O-β-D-glucopyranoside and 4.5 mg β-zearalenol-4O-β-D-glucopyranoside at purities higher than 99%. To confirm the identities of the three produced glucosides, MS and MS/MS spectra were acquired using negative electrospray ionization. Besides the deprotonated ions at m/z 479 or 481, respectively, in full-scan mode, fragments, adducts, and dimers were recorded and assigned. MS/MS spectra of the glucosylated substances yielded the deprotonated ions of the mycotoxins zearalenone, α-zearalenol,β-zearalenol and their fragments, respectively. Unambiguous structural assignment of the three substances was achieved using two-dimensional NMR methods. This way, the glucose attachment to position C-4, the β-configuration of the sugar unit and the stereo-chemical assignment of the zearalenol hydroxyl group at C-6' were proven.