Addition/Correction pubs.acs.org/JAFC
Correction to Enzyme-Assisted Synthesis and Structural Characterization of the 3‑, 8‑, and 15-Glucuronides of Deoxynivalenol Silvio Uhlig,* Lada Ivanova, and Christiane Kruse Fæste J. Agric. Food Chem. 2013, 61 (8), 2006−2012. DOI: 10.1021/jf304655d S Supporting Information *
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TOCSY NMR spectra were run on the isolated DON 8-O-β-Dglucuronide in DMSO-d6, no coupling was observed from the H-15 protons to a hydroxyl proton. Thus, we conclude that the product of our microsomal synthesis was a cyclic hemiketal DON 8-O-β-D-glucuronide (3) according to Figure 1, and not a ketal as originally suggested.
e previously reported the enzyme-assisted synthesis of three glucuronic acid conjugates of deoxynivalenol (DON, 1) using rat and human liver microsomes.1 The major products were identified as the 3- and 15-O-β-Dglucuronides of 1, whereas a third and minor product was identified as an 8-O-β-D-glucuronide. The interpretation of the NMR spectra of the latter was ambiguous because of the limited amount of available substance and, thus, poor signal/ noise. Still, the attachment of the glucuronide moiety to C-8 was easily shown via HMBC correlations, and the 13C chemical shift of C-8 (110.2 ppm) indicated the presence of a ketal carbon. Our recent investigations into the reactions of 1 with different thiols showed that all reaction products were in equilibrium with a hemiketal derivative (2) as a result of intramolecular addition of the oxygen atom on C-15 to the C-8 carbonyl (Figure 1).2 In the NMR spectra of DON−thiol
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ASSOCIATED CONTENT
S Supporting Information *
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.jafc.6b01413 Selected regions of the HMBC spectra of DON 8-O-β-Dglucuronide and DON 15-O-β-D-glucuronide showing correlations between H-15 and neighboring carbons (PDF)
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REFERENCES
(1) Uhlig, S.; Ivanova, L.; Fæste, C. K. Enzyme-assisted synthesis and structural characterization of the 3-, 8-, and 15-glucuronides of deoxynivalenol. J. Agric. Food Chem. 2013, 61, 2006−2012. (2) Stanic, A.; Uhlig, S.; Solhaug, A.; Rise, F.; Wilkins, A. L.; Miles, C. O. Nucleophilic addition of thiols to deoxynivalenol. J. Agric. Food Chem. 2015, 63, 7556−7566.
Figure 1. Formation of deoxynivalenol 8-O-β-D-glucuronide from deoxynivalenol 8,15-hemiketal.
adducts we found several spectral features that were characteristic for DON hemiketal derivatives.2 These included a substantially smaller geminal coupling constant of the H-15 proton pair (i.e., 8.1−8.9 vs 10.4−11.9 Hz) and the absence of coupling of the H-15 protons to the hydroxyl proton (in nonhydroxylic solvents).2 In contrast, the H-15 protons of 1 in acetonitrile-d3 appeared as a pair of doublets of doublets (J ≈ 12.6 Hz) due to coupling to the 15-hydroxyl.2 The 2JH−H coupling constant of the H-15 proton pair was 8.8 Hz in the 8glucuronide versus 10.4 and 11.9 Hz in the 15- and 3glucuronides, respectively.1 In addition, one of the H-15 protons in the 8-glucuronide showed a HMBC correlation to C-8 at 110.2 ppm (three-bond correlation), whereas such a correlation was not observed in the C-3 and C-15 glucuronides (four-bond correlation). Furthermore, when 1H and SEL© XXXX American Chemical Society
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DOI: 10.1021/acs.jafc.6b01413 J. Agric. Food Chem. XXXX, XXX, XXX−XXX
