Date of Award
Doctor of Philosophy (PhD)
School of Nutrition and Food Sciences
Douglas L. Park
The current study evaluated interactions between the mycotoxins aflatoxin B$\sb1$ (AFB$\sb1$) and fumonisin B$\sb1$ (FB$\sb1$) in pure systems as well as in corn. During storage at 25$\sp\circ$C with high moisture (ca. 50%), corn contaminated with Aspergillus flavus (L13) and/or Fusarium moniliforme (A00102) presented different aflatoxin and fumonisin levels. Toxin production/degradation varied over storage time (0-45 days). Evaluation of the mutagenicity of unifungal or bifungal corn extracts with the Salmonella/microsomal assay (tester strains TA-100 and TA-98) with metabolic activation (S9) showed positive mutagenic responses. Different ratios of pure AFB$\sb1$/FB$\sb1$ produced divergent mutagenic responses (tester strains TA-100 and TA-98) with S9. The mutagenicity of 10$\sp3$ ng AFB$\sb1$/plate was reduced by addition of 1 to 10$\sp2$ ng FB$\sb1$/plate. Higher FB$\sb1$ concentrations (10$\sp3$ to 10$\sp5$ ng/plate) caused an opposite effect. The mutagenic potential of 2-aminofluorene (2-AF) was also affected by FB$\sb1.$ This suggested that FB$\sb1$ affects the enzyme systems responsible for activating AFB$\sb1$ and 2-AF. Analysis by liquid chromatography of AFB$\sb1$/AFB$\sb1$-metabolites after reaction with FB$\sb1$ and S9 showed decreased recovery when 10$\sp3$ ng AFB$\sb1$ were exposed to 1 to 10$\sp2$ ng FB$\sb1$, but at higher FB$\sb1$ levels (10$\sp3$ to 10$\sp5$ ng), recovery was increased. Thin layer chromatography analysis of these samples suggested that unidentified AFB$\sb1$-metabolites derivatized with trifluoroacetic acid were indirectly detected as AFB$\sb1.$. FB$\sb1$ (1 to 10$\sp5$ ng/plate) inhibited gap-junction intercellular communication of Clone-9 rat liver cells. This could be a possible mechanism by which FB$\sb1$ acts as a non-genotoxic carcinogen. Addition of 1 to 10$\sp3$ ng AFB$\sb1$ to 10$\sp5$ ng FB$\sb1$ did not change the effect of FB$\sb1.$ An increase in the uptake of neutral red by Clone-9 rat liver cells exposed to AFB$\sb1$/FB$\sb1$ implied that peroxisome proliferation and oxidative metabolism may be involved in AFB$\sb1$/FB$\sb1$ interactions. H$\sb2$O$\sb2$ (3%) and NaHCO$\sb3$ (2%) were effective in decontaminating/detoxifying aflatoxin-fumonisin naturally co-contaminated corn without generating mutagenic by-products. This study showed preliminary evidence that simultaneous exposure to AFB$\sb1$/FB$\sb1$ can give different toxicological responses than single exposure to either of these compounds. More research is needed to better assess the toxicological impact of AFB$\sb1$/FB$\sb1$ co-contamination and to develop possible control strategies.
Lopez-garcia, Rebeca, "Aflatoxin B(1) and Fumonisin B(1) Co-Contamination: Interactive Effects, Possible Mechanisms of Toxicity, and Decontamination Procedures." (1998). LSU Historical Dissertations and Theses. 6746.