Fumonisins are mycotoxins produced by Fusarium moniliforme (FM), a major worldwide fungal contaminant of corn, and other Fusarium species. Consumption of FMcontaminated corn has been associated with high incidences of human esophageal cancer in sections of China and southern Africa. One fumonisin, fumonisin B1 (FB1), has been shown to cause equine leukoencephalomalacia and porcine pulmonary edema, fatal FM-induced field toxicoses of horses and swine, respectively. Hepatocarcinomas have been found in male rats chronically fed 50ppm FB1. Fumonisins are inhibitors of de novo sphingolipid biosynthesis in vitro and it has been proposed that in vivo toxicity may result from altered sphingolipid metabolism. Diets containing 0, 1, 3, 9, 27, or 81ppm FB1 were fed to rats and mice for 90days. Although previous studies established that FB 1 is hepatotoxic in rats, FB 1 did not cause liver damage to rats in this study. Nephrosis was found in male rats fed ≥ 9 ppm FB 1 and, to a lesser extent, in females fed 81 ppm FB 1. In contrast FB1 was hepatotoxic in female, but not male, mice fed the 81 ppm diets. Thus, the “no observed effect levels, ” 3 ppm for rats and 27 ppm for mice, and organ-specific effects differed in the two species. In a second, four-week study, sphingolipid metabolism was altered in male and female rats fed 15, 50, or 150 ppm FB1. The degree of tissue injury as determined by serum chemical and morphological endpoints was correlated with the magnitude of renal, hepatic, and urinary sphingolipid profile alterations. These findings support the hypothesis that sphingolipid metabolism plays a role in FB 1 toxigenesis in vivo. Further studies to compare sphingolipid metabolism and toxicity in rats and mice as well as to further study the in vitro and in vivo effects of fumonisins on sphingolipid metabolism are warranted.
The fluorescence emission of chaetochromin A was examined at various conditions and its mode of binding to serum albumin and mitochondrial membrane protein(s) was discussed. Chaetochromin A emitted fluorescence in pyridine and N, N-dimethylformamide (DMFA), and did not in ethanol and benzene. The excitation and emission wavelengths were 415 and 515nm, respectively. Chaetochromin A was not fluorescent in bufferized aqueous solution (pH 7.4). In the presence of BSA, it was fluorescent, exhibiting the pH-dependent alteration of fluore-scence intensity. The magnitude of fluorescence intensity was the largest at pH around 7.5. Chaetochromin A was not fluorescent in the presence of anionic detergent sodium dodecyl sulfate (SDS), but was eminently fluorescent in the presence of cationic detergent benzalkonium chloride (pH 7.4).
Imported corn samples (32 samples) were analyzed for fumonisins using two different methods. Each ground corn sample was extracted with 50% acetonitrile/water. Fumoni-sins were analyzed by both high-performance liquid chromatography (HPLC) using o-phthaldialdehyde (OPA) derivatization method and an enzyme-linked immunosorbent assay (ELISA) test kit system (Agri-Screen for fumonisin, Neogen corp., Michigan, U.S.A.). Concentrations of fumonisins in the samples analyzed by HPLC were as follows; more than 5ppm in one sample, between 1 and 5ppm in 7 samples and between 0.05 and 1ppm in 10 samples. On the other hand, 6 samples were positive for fumonisin in comparison with 5ppm fumonisin B1 standard in the analysis by ELISA test-kit system. The number of fumonisin-contaminated samples detected by using ELISA test-kit system were smaller than that detected by using HPLC but the Agri-Screen ELISA test-kit system is con-venient for quick screening of fumonisins in corn samples.