37 Research Article Received: 22 December 2010 Revised: 16 June 2011 Accepted: 20 July 2011 Published online in Wiley Online Library: 14 October 2011 (wileyonlinelibrary.com) DOI 10.1002/jsfa.4674 A survey of free and conjugated deoxynivalenol in the 2008 corn crop in Ontario, Canada Si-Trung Tran, Trevor K Smith * and George N Girgis Abstract BACKGROUND: Deoxynivalenol (DON, vomitoxin), one of the most important mycotoxins produced by many Fusarium species, is found as a common contaminant of crops worldwide. Recent studies have described the presence of conjugated forms of DON (glycosides and fatty acid). The aim of the current study was therefore to investigate the natural occurrence of free and conjugated DON in Canadian corn. RESULTS: Free and conjugated DON was determined by gas chromatography-mass spectrometry (GC-MS) and enzyme-linked immunosorbent assay (ELISA) in 86 corn samples collected from the 2008 crop in Ontario, Canada. Free DON concentrations determined by ELISA were similar to values determined in most samples using GC-MS. Conjugated DON was detected in 72 samples. Levels of free DON ranged from 0.17 to 14.00 μgg -1 using GC-MS. The highest levels of free DON were found in corn samples from the southern and southwestern regions of Ontario, while samples from eastern regions were less contaminated. Conjugated DON was found mainly in corn from the east-central region, with five of six samples showing high levels of conjugated DON (up to 43% increase in DON following acid hydrolysis). Low levels of conjugated DON (≤10% increase in DON following acid hydrolysis) were detected in the majority of corn samples from the southwestern region (nine of 19 samples) and from the central region (16 of 36 samples). CONCLUSION: The current survey emphasizes the frequency of conjugated DON in Ontario grown corn and the potential challenges in understanding the hazard posed by DON-contaminated foodstuffs and feedstuffs. c  2011 Society of Chemical Industry Keywords: deoxynivalenol; conjugated; corn; Ontario INTRODUCTION Deoxynivalenol (DON) is one of the most common mycotoxins produced by many Fusarium species and is found as a contaminant of cereal grains worldwide. 1–4 DON was first isolated by Vesonder et al. 5 from Fusarium-infected corn in the USA and was named ‘vomitoxin’ because of the capacity to induce emesis in swine. DON has been reported to cause a variety of toxicoses in animals and to potentially affect human health. 6–8 There are marked species differences with respect to sensitivity to DON toxicity. Feed-borne DON can reduce production efficiency and cause serious economic losses to livestock and poultry producers. 9 The most frequent mycotoxin occurring in Canadian-grown grain is DON. 4 Fusarium species are often associated with corn which is immature or high in moisture at harvest. These molds develop under cool and wet conditions, especially during the autumn in the field or in storage in winter. In a previous survey, Andrew et al. 10 reported that the occurrence of mycotoxins in Canada was most frequent in Ontario, particularly in the more humid southern areas such as the Niagara peninsula. Conjugated (masked) mycotoxins have been described as non- detectable using conventional analytical techniques owing to a lack of understanding of their chemical nature and a lack of analytical standards. DON, zearalenone and fumonisin have all been reported to exist in both free and conjugated forms. 11–13 These compounds, moreover, have recently been described as a potential problem in human and animal health because they may be hydrolyzed during digestion, thereby generating free compounds. Conjugated mycotoxins are thought to arise from plant metabolism and are bound to different compounds including glucose, fatty acids, glutathione and hemicellulose. 14–18 The lack of research information on the frequency of conjugated mycotoxins raises uncertainties when regulations are introduced regarding the acceptable levels of mycotoxins in grains for human and animal consumption. A survey of the natural occurrence of free and conjugated DON was conducted, therefore, in an Ontario corn crop. ∗ Correspondence to: Trevor K Smith, Department of Animal and Poultry Science, University of Guelph, 50 Stone Rd E, Guelph, ON N1G 2 W1, Canada. E-mail: tsmith@uoguelph.ca Department of Animal and Poultry Science, University of Guelph, Guelph, ON N1G 2 W1, Canada J Sci Food Agric 2012; 92: 37–41 www.soci.org c  2011 Society of Chemical Industry