Deoxynivalenol (DON) is a mycotoxin commonly contaminating wheat, barley and corn. DON glucuronide (DONGLU) is a major DON metabolite. We synthesized and purified DONGLU and tested its immunotoxicity, hypothesizing that DONGLU would be much less toxic to K562 cells compared with DON. DONGLU was synthesized using rat liver microsomes, uridine-50-diphosphoglucuronic acid and DON, and purified with a Sephadex LH-20 column and reverse phase HPLC. b-Glucuronidase hydrolysis formed a product with retention time and UV spectrum identical with DON. Using atmospheric pressure chemical ionization in negative mode, the molecular mass (M1) of purified DONGLU was 471 g/mol; in agreement with an expected molecular weight of 472 g/mol. MS and NMR indicated that the glucuronide moiety was conjugated with the carbon-3-hydroxyl group of DON. The cytotoxicity of DON and DONGLU were compared in cell culture using human erythroleukemia cell line K562. Fifty percent inhibition of cell number was observed with a DON concentration of 1.31 lM using a methylthaizol tetrazolium (MTS) cell viability assay whereas no significant cytotoxicity was observed for DONGLU at up to 270 lM. DONGLU did not influence DON toxicity at 0.5 lM, 1.3 lM and 8.4 lM concentration combinations of each compound. These data verified that DONGLU is a detoxification product of DON.