Prevalence of non-regulated fungal and other metabolites in South African maize (2017–2019): A multi-year study using LC-MS/MS

Recent improvements in detection techniques, coupled with the impacts of climate change, have uncovered a wide range of previously unregulated fungal metabolites. Non-regulated mycotoxins have recently gained attention in the scientific community due to their high prevalence and concentrations in maize, as well as their unknown toxicity. This study aimed to determine the natural occurrence of non-regulated fungal metabolites in commercial maize intended for human and animal consumption. A total of 752 pre-harvest maize samples were collected from selected silos in three provinces over a three-year harvest season and analyzed using liquid chromatography-tandem mass spectrometry (LC-MS/MS). We detected 105 non-regulated metabolites, with aurofusarin, culmorin, W493, cyclo(L-Pro-L-Val), and cyclo(L-Pro-L-Tyr), being the most frequently detected (above 90 % occurrence in samples) in the range of 3.99–6104.82 µg/kg, 8.29–6292.65 µg/kg, 1.26–2618.40 µg/kg, 3.91–244.84 µg/kg, 4.03–209.18 µg/kg respectively. While the toxicity of most of these metabolites remains understudied, others like 3-nitropropionic acid, sterigmatocystin, diplodiatoxin, aurofusarin, fusaric acid, butenolid, and phomopsolide B, have established toxicities. The high co-occurrence and prevalent concentrations of some of these metabolites raise safety concerns. Therefore, toxicological studies and the establishment of consumption limits for these metabolites are crucial for ensuring food safety.