This dissertation had two objectives. The first was to determine total aflatoxin concentrations in sunflower seeds, cakes and crude oil sediments from small-scale oil processors across Tanzania. The towns selected for sunflower sample collection included Mbeya, Iringa, Morogoro, Dodoma, Singida, Babati-Manyara and Karatu-Arusha. We collected a total of 232 samples: sunflower seed (n = 90), cake samples (n = 92) and crude sunflower oil sediments (n = 50) across two years, which were analyzed for total aflatoxin concentrations using a direct competitive enzyme-linked immunosorbent assay (ELISA). The aflatoxin surveillance performed in June-August 2014, indicated that the highest aflatoxin levels in sunflower seeds were from the towns of Babati-Manyara, Singida, and Dodoma. The aflatoxin levels in sunflower cakes were exceedingly high in Singida, Dodoma, and Mbeya. The surveillance performed in August-October 2015, indicated that the highest aflatoxin concentrations in sunflower seeds were from Mbeya, Singida, and Morogoro. Singida, Dodoma, and Morogoro had shown unacceptable aflatoxin levels in sunflower cakes. Aflatoxin levels in oil sediments were considerably lower in both years except Morogoro, which showed two oil sediments exceedingly contaminated (41.7 and 85.3 ng/g). Concerning risk assessment, Dodoma and Babati-Manyara showed dietary exposures of 25 and 21 ng/kg bw/day, respectively, for sunflower seed consumption in 2014. Liver cancer risks for these exposures were 0.9 and 0.8 cases per year per 100,000 individuals, respectively. Samples from Morogoro suggested dietary exposure of 24 ng/kg bw/day for sunflower seed consumption in 2015 that carried a risk of 0.9 cases per year per 100,000 individuals. Although the crude oil sediment data showed that crude oils were safe, the general results of aflatoxin levels in seeds and cakes particularly from Manyara, Singida, Dodoma and Morogoro, and crude oil sediments from Morogoro, indicate that there is a potential risk of exposure to aflatoxin through sunflower products and intervention strategies are required. Our second objective was to determine the anti-aflatoxigenic properties of compounds from a traditional medicinal plant D. mafiensis root bark against vegetative growth, sporulation and aflatoxin production by Aspergillus flavus and Aspergillus parasiticus. The bioactive compounds diosquinone (DQ) and 3-hydroxydiosquinone (3HDQ) were elucidated and identified using 1H- and 13C-NMR and LC-MS methods. Growth inhibition was determined by measuring the colony diameters of the molds in culture. Total aflatoxin was quantified by direct competitive enzyme-linked immunosorbent assay (ELISA). DQ showed weak potency against A. flavus and A. parasiticus vegetative growth (MIC50 >100 μg/mL), and 3HDQ demonstrated a strong potency against A. flavus (MIC50 = 14.9 μg/mL) and A. parasiticus (MIC50 = 39.1 μg/mL). Despite its weak potency against vegetative growth, DQ strongly reduced total aflatoxin production by A. flavus and A. parasiticus for over 90 %. Counterintuitively, 3HDQ stimulated aflatoxin production by A. flavus at lower doses but started to reduce aflatoxin production at the dose of 100 μg/mL. 3HDQ strongly reduced total aflatoxin production by A. parasiticus even at lower doses. In summary, DQ and 3HDQ could be used as natural fungicides to prevent mold growth and aflatoxin accumulation in food and feed.
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