Occurrence of mycotoxins in Nigerian food commodities and health risk assessment

M.Tech.A variety of fungal species belonging to the genera Aspergillus, Penicillium, Fusarium and Alternaria, Cladosporium are common contaminants of food commodities such as grains, cereals, seeds, nuts, and fruits. These fungal species in turn produce mycotoxins under favourable conditions as secondary metabolites, which have been recorded to have harmful effects in both animals and man. The concern for mycotoxin contamination of food commodities grown and produced in sub-Saharan Africa has grown considerably over the years with increased and improved strategies on mycotoxin monitoring. The aim of this project was to determine and evaluate the quality of food commodities grown and produced in selected rural areas of the southern part of Nigeria in relation to fungi and mycotoxins, evaluate the health implications of the mycotoxins, as well as, suggest possible solutions to reduce exposure of the population in these areas to fungi and mycotoxins in the food. This study was of much importance as the populace of these areas depend solely on the food commodities grown and produced in these areas. Ochratoxin A, aflatoxins, deoxynivalenol, fumonisins and zearalenone are major mycotoxins occurring naturally in most food commodities that have important health significances and as such, it was important to determine the exposure of people in this part of the country to these major mycotoxins. A total of 144 samples comprising of rice (41), maize (39), cocoa (39) and cocoa-based powder beverage (25) collected from the fields, markets and stores were screened for Aspergillus, Fusarium and Penicillium species producing mycotoxins using conventional methods and DNA sequencing which were preceded by serial dilution of samples on agar plates. Further analysis for mycotoxin extraction was done using multi-mycotoxin extraction, strong anion exchange columns and immunoaffinity columns, which was followed by identification and quantification via thin layer chromatography (TLC) and high performance liquid chromatography (HPLC). Mycological screening of samples showed incidences of various species of filamentous fungi including A. flavus, A. parasiticus, A. ochraceus, A. niger, F. verticillioides, F. proliferatum and F. graminearum, with highest incidences of A. flavus in rice (65.9%), F. verticillioides in maize (76.9%), A. flavus in cocoa (77.8%) and Cladosporium in cocoa-based powder beverages (32%). Mycotoxicological analysis showed occurrences of aflatoxins, ochratoxin A, zearalenone, fumonisins and deoxynivalenol in all food samples analysed with fumonisins, aflatoxins, ochratoxin A and deoxynivalenol prevalent in maize samples; ochratoxin A, aflatoxins and fumonisisn prevalent in rice samples; aflatoxins, ochratoxin A and fumonisins prevalent in cocoa samples and ochratoxin A, fumonisins and zearalenone prevalent in cocoa-based powder beverage samples. Levels of mycotoxin contamination varied from field to market place to storage with higher contamination of mycotoxins in samples from markets and store houses. In order to determine the health implications of the extracted mycotoxins, cytotoxicity analysis was done using MTT (methylthiozol tetrazolium)- assay on human blood lymphocytes and results showed a reduction in cell viabilities on cells exposed to extracts contaminated with mycotoxins at varying concentrations over 24hrs and 48hrs duration. It was seen that although levels of mycotoxins in samples were below and some above the set regulatory limits of mycotoxins in food, daily exposure to these mycotoxins over a long period of time could be dangerous health-wise influencing symptoms such as immunosuppression, kidney disorders, reproductive health disorders, liver and oesophageal cancers. It is therefore necessary to educate rural population and other populace on the health implications of ingesting these mycotoxins as well as teach them simple and cheap methods of preventing mycotoxin contamination of food commodities