Journal
PHYTOCHEMISTRY
Volume 77, Issue -, Pages 171-178Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.phytochem.2012.01.019
Keywords
Zea mays; Triticum aestivum; Electrophile; Thiol reactivity; Benzoxazinone; DIMBOA; Glutathione
Categories
Funding
- Biotechnology and Biological Sciences Research Council [BBC51227X1]
- Engineering and Physical Sciences Research Council [EP/G05021X/1] Funding Source: researchfish
- EPSRC [EP/G05021X/1] Funding Source: UKRI
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Maize, wheat and other grasses synthesise large quantities of benzoxazinones and their glucosides, which act as antifeedant and allelopathic agents. These activities are probably due to the electrophilic nature of the aglycones, however, the mechanism of their action is unclear. In biological systems, glutathione (GSH) is the major electrophile-reactive compound so the reaction of the major maize benzoxazinone DIMBOA with GSH was studied. GSH reacts with DIMBOA to form eight isomeric mono-conjugates and eight isomeric di-conjugates. Through NMR studies with the model thiol 2-mercaptoethanol, these were structurally elucidated as unusual spirocycles. Similar reactivity was observed with proteins, with cysteinyl thiols being modified by DIMBOA. The thioether bonds formed were stable and not easily reduced to the parent thiol. DIMBOA can therefore readily deplete GSH levels and irreversibly inactivate enzymes with active-site cysteine residues, with clear implications for potentially toxic effects when young grasses are ingested, whether by insect pests or humans. (C) 2012 Elsevier Ltd. All rights reserved.
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