Intestinal hydrolysis and microbial biotransformation of diacetoxyscirpenol-a-glucoside, HT-2-ß-glucoside and N-(1-deoxyd-d-fructos-1-yl) fumonisin B1 by human gut microbiota in vitro

Authors: DAUD, NOSHIN - University Of Aberdeen; CURRIE, VALERIE - University Of Aberdeen; DUNCAN, GARY - University Of Aberdeen; Busman, Mark; GRATZ, SILVIA - University Of Aberdeen

Submitted to: International Journal of Food Sciences and Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/24/2019
Publication Date: 12/3/2019
Citation: Daud, N., Currie, V., Duncan, G., Busman, M., Gratz, S.W. 2019. Intestinal hydrolysis and microbial biotransformation of diacetoxyscirpenol-a-glucoside, HT-2-ß-glucoside and N-(1-deoxyd-d-fructos-1-yl) fumonisin B1 by human gut microbiota in vitro. International Journal of Food Sciences and Nutrition. 71(5):540-548. https://doi.org/10.1080/09637486.2019.1698015.
DOI: https://doi.org/10.1080/09637486.2019.1698015

Interpretive Summary: Mycotoxins produced by fungi can contaminate cereals and other crops and represent a threat to food safety and animal health. Detection and accurate quantitation of these toxins in food and feed is critical to reducing exposure. However, plants are able to modify these toxins, creating masked forms that are often less toxic, but not detected by normal toxin assays. In this study, we used a simulated gut to assess the metabolism of masked mycotoxins by gut microbes. We demonstrated that microbes found in the human gut convert masked forms of trichothecene and fumonisin mycotoxins into their parent compounds at rates that were dependent on the masked toxin and the human volunteer sampled. The results indicate that gut metabolism of grain contaminated with masked versions of the tested toxins may result in exposure to the parent toxin and potentially increased toxicity. We also demonstrated that chemically related mycotoxins are metabolized at different rates, necessitating careful evaluation of each new modified mycotoxin. This work provides a tool for regulators to conduct effective risk assessments for grain-based products contaminated with masked mycotoxins.

Technical Abstract: Fusarium mycotoxins are common contaminants in cereals and often co-occur with plant-derived mycotoxin sugar conjugates. Several of these modified mycotoxins are not degraded in the small intestine and hence carried through to the large intestine where microbial transformation may occur. This study aims to assess the gastrointestinal stability of the trichothecenes HT-2 toxin (HT-2), HT-2-b-glucoside (HT-2-Glc), diacetoxyscirpenol (DAS), DAS-a-glucoside (DAS-Glc) and fumonisin B1 (FB1), N-(1-deoxy-D-fructos-1-yl) fumonisin-B1 (NDF-FB1). All tested modified mycotoxins were stable under upper gastrointestinal (GI) conditions. In faecal batch culture experiments, HT-2-Glc was hydrolysed efficiently and no further microbial biotransformation of HT-2 was observed. DAS-Glc hydrolysis was slow and DAS was de-acetylated to 15-monoacetoxyscripenol. NDF-FB1 was hydrolysed at the slowest rate and FB1 accumulation varied between donor samples. Our results demonstrate that all tested modified mycotoxins are stable in the upper GI tract and efficiently hydrolysed by human gut microbiota, thus potentially contributing to colonic toxicity. Hence the microbial biotransformation of any novel modified mycotoxins needs to be carefully evaluated.