Toxicological effects in rats chronically fed low dietary levels of fumonisin B(1)

The toxicity of low dietary levels of fumonisin B(1) (FB(1)), i.e. 1, 10 and 25 mg FB(1)/kg diet, were monitored in rats over a period of 24 months. No effects on the body weight gain and feed intake profiles were noticed, while the relative liver weight was significantly (P<0.05) reduced in the FB(1)-treated rats. Mild toxic effects, including single cell necrosis (apoptosis), proliferation of bile duct epithelial cells (DEC), and early signs of fibrosis, bile duct hyperplasia and in one case, adenofibrosis, were noticed in the liver of the rats fed the highest (25 mg/FB(1)/kg diet) dietary level. A significant (P<0.05) increase in the level of oxidative damage was also noticed in the liver of the rats of high dosage dietary group. The toxic effects were less severe in the 10 mg FB(1)/kg dietary group, whilst only a few ground glass foci were observed in the 1 mg FB(1)/kg dietary group. Hepatocyte nodules, staining positively for glutathione-S-transferase (placental form, PGST), were observed macroscopically in the 25 mg FB(1)/kg treated group and to a lesser extent in the 10 mg FB(1)/kg treated rats. The most prominent toxic lesions by FB(1) (10 and 25 mg FB(1)/kg dietary groups) in the kidneys were restricted to the tubular epithelium manifesting as granular cast, necrosis, apoptosis, calcification and the presence of regenerative foci in the proximal convoluted tubules. The existence of a cytotoxic/proliferative threshold with respect to cancer induction by FB(1) in rat liver became apparent, with a dietary level of <10-mg FB(1)/kg diet as a no effect threshold for the induction of hepatocyte nodules.     

Effects of orally administered fumonisin B1 (FB1), partially hydrolysed FB1, hydrolysed FB1 and N-(1-deoxy-D-fructos-1-yl) FB1 on the sphingolipid metabolism in rats

Fumonisin B₁ (FB₁) is a Fusarium mycotoxin frequently occurring in maize-based food and feed. Alkaline processing like nixtamalisation of maize generates partially and fully hydrolysed FB₁ (pHFB₁ and HFB₁) and thermal treatment in the presence of reducing sugars leads to formation of N-(1-deoxy-D-fructos-1-yl) fumonisin B₁ (NDF). The toxicity of these metabolites, in particular their effect on the sphingolipid metabolism, is either unknown or discussed controversially. We produced high purity FB₁, pHFB₁a+b, HFB₁ and NDF and fed them to male Sprague Dawley rats for three weeks. Once a week, urine and faeces samples were collected over 24 h and analysed for fumonisin metabolites as well as for the sphinganine (Sa) to sphingosine (So) ratio by validated LC–MS/MS based methods. While the latter was significantly increased in the FB₁ positive control group, the Sa/So ratios of the partially and fully hydrolysed fumonisins were indifferent from the negative control group. Although NDF was partly cleaved during digestion, the liberated amounts of FB₁ did not raise the Sa/So ratio. These results show that the investigated alkaline and thermal processing products of FB₁ were, at the tested concentrations, non-toxic for rats, and suggest that according food processing can reduce fumonisin toxicity for humans.     

The effect of a single gavage dose of fumonisin B(1) on the sphinganine and sphingosine levels in vervet monkeys.

This is the first report of sphinganine (Sa) and sphingosine (So) levels determined in serum and urine of vervet monkeys (Cercopithecus aethiops) dosed with pure fumonisin B(1) (FB(1)). Initially, experimental vervet monkeys were given a single gavage dose of either 1 or 10 mg FB(1) /kg body weight. Blood and urine were sampled daily and on day seven the monkeys were terminated and the kidneys and livers harvested. In a subsequent experiment, other vervet monkeys were similarly dosed and blood and urine samples were collected over a 50-day period. In the high-dose monkeys the serum Sa/So ratio, as well as levels of serum cholesterol and liver function enzymes, increased during the first week after dosing and remained elevated for several weeks thereafter. The urinary Sa/So ratio and the serum renal function indicators showed a more rapid response and a correspondingly more rapid return to pre-dosing levels. In the low-dose monkeys serum Sa and the Sa/So ratio were the only parameters to increase above the control levels. The Sa/So ratio in liver and kidney tissue showed an elevation over controls in a dose-dependent manner. The serum Sa/So ratio was exclusively elevated above the control levels in the low- and high-dose monkeys and seems more relevant as a marker for fumonisin exposure than any of the other indicators.     

The effect of repeated gavage doses of fumonisin B1 on the sphinganine and sphingosine levels in vervet monkeys.

Fumonisins occur widely around the world in maize products intended for human and animal consumption posing a health hazard. Direct measurement of fumonisins in physiological fluids as a biomarker of exposure is not practicable, however fumonisins disrupt sphingoid metabolism by inhibition of sphinganine N-acyltransferase. In this study the disruption in sphinganine (Sa) and sphingosine (So) levels in plasma and urine was measured in vervet monkeys (Cercopithecus aethiops) dosed with repeated gavages of 1mg fumonisin B1 (FB1)/kg body weight three times/week continuously over a 51-day period. The plasma Sa/So ratio reached a maximum (mean of 4.3) after 30 days in the dosed monkeys with a three-fold increase above the ratio of the control monkeys and then declined slowly to double the value in controls after 51 days. The lack of a clear elevation in urinary Sa/So ratios after 51 days of multiple exposure in the dosed monkeys indicates that the plasma ratio is more sensitive than urinary changes in monkeys. This is confirmed by the plasma levels of liver function enzymes of which aspartate transaminase, glutamyl-transferase and lactate dehydrogenase were increased in the dosed monkeys, while the plasma indicators of renal function were not increased above the levels in the control monkeys. Thus repeated low doses of FB1 can cause sustained disruption of sphingoid metabolism.     

Effects of aflatoxin B(1) and fumonisin B(1) on blood biochemical parameters in broilers

The individual and combined effects of dietary aflatoxin B(1 )(AFB(1)) and fumonisin B(1) (FB(1)) on liver pathology, serum levels of aspartate amino-transferase (AST) and plasma total protein (TP) of broilers were evaluated from 8 to 41 days of age. Dietary treatments included a 3 × 3 factorial arrangement with three levels of AFB(1 )(0, 50 and 200 μg AFB(1)/kg), and three levels of FB(1 )(0, 50 and 200 mg FB(1)/kg). At 33 days post feeding, with the exception of birds fed 50 mg FB(1 )only, concentrations of AST were higher (p < 0.05) in all other treatment groups when compared with controls. Plasma TP was lower (p < 0.05) at six days post feeding in groups fed 200 μg AFB(1)/kg alone or in combination with FB(1). At day 33 days post feeding, with the exception of birds fed the highest combination of AFB(1 )and FB(1 )which had higher plasma TP than control birds(, )plasma TP of birds fed other dietary treatments were similar to controls. Broilers receiving the highest levels of AFB(1) and FB(1) had bile duct proliferation and trabecular disorder in liver samples. AFB(1) singly or in combination with FB at the levels studied, caused liver damage and an increase in serum levels of AST.     

Toxic effects of Ustilago maydis and fumonisin B1 in rats

The toxicity of Ustilago maydis and the possible synergism with fumonisin B1 (FB1) were studied in Fischer rats by evaluating pathological changes and biochemical parameters in blood serum (LDH, ALT, GGT, ChE) and tissue homogenate of brain and liver (AChE, ChE, GGT, ALP). One experimental group (US) consumed diet with 70% of U. maydis galls and the other group (US+FB1) was fed pellets containing 70% of U. maydis galls and 1 mg of FB1 per kg of diet for 17 days. Control group (C) consumed standard pellets. During the trial, experimental animals were more excited, showing hyperactivity. Body mass gains slightly increased in both groups compared to the control. Gross pathological changes in liver, lungs, uterus and ovaries were more pronounced in the US+FB1 than in the US group. Specific catalytic activities of AChE decreased by 61% and by 63% in the liver and brain homogenate of the US group (p<0.05) compared to the control, indicating neurotoxic activity of U. maydis. Also, specific catalytic concentration of AChE and ALP was significantly decreased in the liver of the US+FB(1) group (p<0.05). Activity of LDH in the blood serum was increased up to 166% and 165% in the US+FB1 group (p<0.05) compared to the control and US group values, respectively, which indicates that FB1 was responsible for the disruption of cell membrane integrity. These findings suggest that Ustilago maydis and FB1 showed neurotoxicity in Fischer rats, which could be related to the alkaloids of U. maydis and disruption of sphingolipid metabolism by FB1 activity.     

Differential effects of fumonisin B1 on cell death in cultured cells: the significance of the elevated sphinganine

Fumonisins are specific inhibitors of ceramide synthase in sphingolipid metabolism. An alteration in sphingolipid metabolism as a result of fumonisin exposure is related to cell death (Yoo et al., 1992). The objective of this study was to investigate whether elevated free sphinganine levels are related to the sensitivity of cultured cells to fumonisin exposure. Fumonisin B1 elevated the intracellular free sphinganine concentraions in both LLC-PK1 and Chinese hamster ovary (CHO) cells. However, CHO cells are resistant to fumonisin cytotoxicity at 50 microM, while LLC-PK1 cells are sensitive at concentrations greater than 35 microM. The intracellular concentration of free sphinganine in LLC-PK, cells treated at 50 microM fumonisin B1 for 72 h was approximately 1450 pmol/mg protein relative to the 37 pmol observed in the control culture. Under the same conditions, the population of apoptotic cells in the 50 M fumonisin B1-treated culture was approximately 37% of the total compared to 12% in the control. The caspase III-like activity after 72 h in the 50 microM fumonisin B1-exposed culture increased to approximately 50 pmol/mg protein/hr compared to 6 pmol/mg protein/hr in the control. L-cycloserine, a serine palmitoyltransferase inhibitor, reduced the fumonisin B1-stimulated caspase III-like activity down to the control level. Under the same culture conditions, the intracellular concentration of free sphinganine after L-cycloserine plus fumonisin B1 treatment was 140 pmol/mg protein compared to 1450 pmol/mg protein in fumonisin B1 alone. The intracellular concentration of free sphinganine in CHO cells treated with 50 microM fumonisin B1 for 72 h was approximately 460 pmol/mg protein, indicating that the mass amount of elevated free sphinganine in the CHO cells was about 32% of that in LLC-PK1 cells. Adding exogenous sphinganine to the CHO cells along with 50 microM fumonisin B1 treatment for 72 h caused both necrosis and apoptosis. In conclusion, the elevated endogenous sphinganine acts as a contributing factor to the fumonisin-induced cell death.     

The effect of a single gavage dose of fumonisin B(2) on the sphinganine and sphingosine concentrations in vervet monkeys.

The disruption in sphinganine (Sa) and sphingosine (So) concentrations in plasma and urine of vervet monkeys (Cercopithecus aethiops) was measured following a single gavage dose of either 1 (low dose) or 10 mg (high dose) fumonisin B(2) (FB(2))/kg body weight. Blood and urine were collected over a 51-day period. In the low-dose monkeys, none of the parameters measured increased significantly above the control values. In the high-dose monkeys the plasma Sa/So ratios were significantly increased (P< 0.05) above the corresponding control ratios after 3 days and continued to be significantly raised for another 27 days, whereafter the ratios declined to control values after 51 days. The plasma aspartate transaminase (AST) activities increased significantly above their control values from day 5 to day 23 and the gamma-glutamyl transferase (GGT) activities from day 7 until the end of the study period. The plasma cholesterol concentration and alanine transaminase (ALT) and lactate dehydrogenase (LDH) activities increased transiently, but not significantly, and returned to control values within the study period. The urinary Sa/So ratio, plasma creatinine and urea values in both groups of monkeys did not increase above the control values. This study demonstrated that a single large dose of FB(2) can cause transient disruption of sphingoid metabolism in vervet monkeys.     

Interaction of fumonisin B(1) and aflatoxin B(1) in a short-term carcinogenesis model in rat liver

The co-existence of the fumonisin and aflatoxin mycotoxins in corn merited studies to investigate their possible synergistic toxicological and carcinogenic effects. When utilising a short-term carcinogenesis model in rat liver, both the compounds exhibited slow cancer initiating potency as monitored by the induction of foci and nodules stained positively for the placental form of gluthatione-S-transferase (GSTP(+)). However, when rats were treated in a sequential manner with AFB(1) and FB(1) the number and size of GSTP(+) lesions significantly increased as compared to the separate treatments. Histopathological analyses indicated that the individual treatments showed far less toxic effects, including occasional hepatocytes with dysplastic nuclei, oval cell proliferation and, in the case of FB(1), a few apoptotic bodies in the central vein regions. The sequential treatment regimen induced numerous foci and dysplastic hepatocyte nodules, and with oval cells extending from the periportal regions into the centrilobular regions. This would imply that, in addition to the cancer promoting activity of FB(1) of AFB(1)-initiated hepatocytes, the AFB(1) pre-treatment enhanced the FB(1) initiating potency, presumably by rendering the liver more susceptible to the toxic effects of FB(1). The co-occurrence of AFB(1) and FB(1) in corn consumed as a staple diet could pose an increased risk and should be included in establishing risk assessment parameters in humans.     

Standard and Fpg-modified comet assay in kidney cells of ochratoxin A- and fumonisin B(1)-treated rats

The effect of ochratoxin A (OTA), fumonisin B(1) (FB(1)), and their combinations on DNA damage was studied using the standard alkaline comet assay and the Fpg-modified comet assay. Rats were orally receiving OTA (5 ng/kg b.w., 0.05 mg/kg b.w., and 0.5mg/kg b.w., respectively) for 15 days, FB(1) (200 ng/kg b.w., 0.05 mg/kg b.w., and 0.5mg/kg b.w., respectively) for 5 days, and the combinations of two lower OTA and FB(1) doses. The tail length, tail intensity, and Olive tail moment (OTM) obtained with the standard comet assay and Fpg-modified comet assay were significantly higher in treated animals than in controls, even at the lowest dose of OTA or FB(1) (p<0.01). The Fpg-modified comet assay showed significantly greater tail length, tail intensity, and OTM in all treated animal than did the standard comet assay (p<0.05), which suggests that oxidative stress is likely to be responsible for DNA damage. DNA damage detected by the standard comet assay at all OTA or FB(1) doses indicates that some other mechanism is also involved. Combined OTA+FB(1) treatment measured either by the standard comet or the Fpg-modified comet assay showed a synergistic increase in the tail intensity and OTM in kidney cells, even at doses that correspond to the daily human exposure in Europe.     

Elevation of sphinganine 1-phosphate as a predictive biomarker for fumonisin exposure and toxicity in mice

Fumonisins are specific inhibitors of ceramide synthase in sphingolipid metabolism. An alteration in sphingolipid metabolism as a result of fumonisin B1 (FB1) exposure is related to cell death, and sphinganine/sphingosine ratio has been used as an indicator of fumonisin exposure in animals. The objective of this study was to investigate a new biochemical marker for the prediction of fumonisin-induced toxicity. When mice were treated with FB1 (10 mg/kg ip/d) for 5 d, the serum levels of sphingoid bases and their 1-phosphate were markedly elevated. The accumulation of sphingosine 1-phosphate (So-1-P) and sphinganine 1-phosphate (Sa-1-P) in serum following FB1 treatment was more apparent than elevated levels of sphingosine (So) and sphinganine (Sa). Sa-1-P/So-1-P ratio in serum was more elevated than Sa/So ratio following fumonisin B1 treatment, indicating that phosphorylation of sphingoid bases may be a sensitive biomarker for fumonisin exposure. In addition, the tissue levels of Sa and Sa-1-P were also significantly elevated in kidneys, liver, heart, lung and brain. FB1-induced toxicity was confirmed microscopically in both liver and kidneys. Liver lesions consisted of centrilobular hypertrophy and cytoplasmic vacuolization. In addition, hepatic binucleated cells were increased and acidophilic body was observed in FB1-treated mice. Kidney lesions were consistent with tubular nephrosis, and tubules were dilated and contained cell debris in FB1-exposed mice. These results suggested that the elevation of Sa-1-P as well as Sa in serum would be a specific biomarker for predicting FB1 exposure, and elevated tissue levels of Sa-1-P may be related to fumonisin toxicity in animals.     

S-adenosylmethionine or 5'-methylthioadenosine are unable to prevent fumonisin B1 hepatotoxicity in mice despite increased oxidation in liver

Fumonisins are mycotoxins produced by the fugus Fusarium verticillioides, a common fungus growing on corn. Fumonisin B(1) (FB(1)) is the most toxic and prevalent fumonisin detected in corn and corn-based foods. It produces species-, gender-specific damage, and is hepatotoxic and nephrotoxic in rodents. Disruption of sphingolipid metabolism resulting from inhibition of ceramide synthase leads to alterations of cell signaling events, particularly tumor necrosis factor (TNF)alpha signal pathways and to the toxic effects of FB(1). It has been reported that FB(1) toxicity involves oxidative stress. S-adenosylmethionine (SAM) and methylthioadenosine (MTA), an intermediate metabolite in SAM metabolism, are hepatoprotective by modulating TNFalpha expression and increasing reduced glutathione (GSH) levels. The current study investigated the effects of SAM and MTA on FB(1) hepatotoxicity in C57BL/6N mice. The animals were given SAM or MTA by intraperitoneal injection of 25 mg kg(-1) body weight every 12 h when they received subcutaneous injection of 2.25 mg FB(1) kg(-1) body weight once daily for 5 days. The results showed that neither SAM nor MTA protected FB(1)-induced liver damage indicated by the increases in activities of plasma alanine aminotransferase and aspartate aminotransferase as well as the number of apoptotic hepatocytes. Both agents prevented an increase of free sphingosine but not sphinganine. Neither SAM nor MTA modified the FB(1)-induced expression of TNFalpha, interleukin (IL)-1alpha or IL-1 receptor antagonist. The decreased GSH in liver following FB(1) treatment was not protected by either agent. The data indicate that SAM and MTA are ineffective in protecting against FB(1) toxic effects.     

Lupus-prone NZBWF1/J mice, defective in cytokine signaling, are resistant to fumonisin hepatotoxicity despite accumulation of liver sphinganine

Fumonisin B1 (FB1) is a mycotoxin produced by Fusarium verticillioides, commonly present in corn and other cereals. Exposure to FB1 causes organ-specific diseases in various species, e.g., equine leukoencephalomalacia and porcine pulmonary edema; in mice the response is hepatotoxicity. We earlier reported that ceramide synthase inhibition by FB1, the initial biochemical effect of this mycotoxin, results in modulation of cytokine network in response to accumulated free sphingoid bases. In the current study we used NZB/NZW-F1 (NZBW) mice that have modified cytokine expression and develop lupus beginning at 5 months of age. The NZBW and C57BL/6J (CBL) mice (appropriate control) were given five daily subcutaneous injections of either saline or 2.25 mg FB1/kg/day and euthanized 24 h after the last treatment. Peripheral leukocyte counts were higher after exposure to FB1 in CBL but not in NZBW. FB1 treatment caused increases of plasma alanine aminotransferase and aspartate aminotransferase activity in CBL mice indicating hepatotoxicity; no elevation of circulating liver enzymes was recorded in NZBW mice. Hepatotoxic responses were confirmed by microscopic evaluation of apoptotic cells. The FB1-induced proliferation of cells observed in CBL strain was abolished in NZBW animals. The sphinganine accumulation in liver after FB1 was equal in both strains of mice. The NZBW strain lacked the FB1-induced increases in the expression of liver tumor necrosis factor alpha, interferon gamma, receptor interacting protein (RIP), and tumor necrosis factor alpha-related apoptosis-inducing ligand (TRAIL), observed in CBL. Results confirmed our hypothesis that initial altered sphingolipid metabolism caused by FB1 leads to perturbation of liver cytokine network and ultimate cellular injury; the mice deficient in cytokine signaling are refractory to FB1 hepatotoxicity.     

Calcium montmorillonite clay reduces AFB1 and FB1 biomarkers in rats exposed to single and co‐exposures of aflatoxin and fumonisin

Aflatoxins (AFs) and fumonisins (FBs) can co‐contaminate foodstuffs and have been associated with hepatocellular and esophageal carcinomas in humans at high risk for exposure. One strategy to reduce exposure (and toxicity) from contaminated foodstuffs is the dietary inclusion of a montmorillonite clay (UPSN) that binds AFs and FBs in the gastrointestinal tract. In this study, the binding capacity of UPSN was evaluated for AFB₁, FB₁ and a combination thereof in Fischer 344 rats. Rats were pre‐treated with different dietary levels of UPSN (0.25% or 2%) for 1 week. Rats were gavaged with a single dose of either 0.125 mg AFB₁ or 25 mg FB₁ per kg body weight and a combination thereof in the presence and absence of an aqueous solution of UPSN. The kinetics of mycotoxin excretion were monitored by analyzing serum AFB₁‐albumin, urinary AF (AFM1) and FB₁ biomarkers over a period of 72 h. UPSN decreased AFM1 excretion by 88–97%, indicating highly effective binding. FB₁ excretion was reduced, to a lesser extent, ranging from 45% to 85%. When in combination, both AFB₁ and FB₁ binding occurred, but capacity was decreased by almost half. In the absence of UPSN, the combined AFB₁ and FB₁ treatment decreased the urinary biomarkers by 67% and 45% respectively, but increased levels of AFB₁‐albumin, presumably by modulating its cytochrome metabolism. UPSN significantly reduced bioavailability of both AFB₁ and FB₁ when in combination; suggesting that it can be utilized to reduce levels below their respective thresholds for affecting adverse biological effects. Copyright © 2013 John Wiley & Sons, Ltd.     

Initial studies on the toxicokinetics of fumonisin B1 in rats.

Fumonisin B1 (FB1), the major compound in the fumonisin group of secondary metabolites of Fusarium moniliforme Sheldon, is associated with some human and animal diseases. After intraperitoneal dosing to rats (7.5 mg/kg), FB1 was rapidly absorbed and reached a maximum concentration in plasma within 20 min after injection. Thereafter, it underwent rapid removal from plasma, displaying a mono-exponential elimination phase that fitted a one-compartment model with a half-life of 18 min. Collection of 24- and 48-hr urine samples indicated that only 16% of the applied dose was eliminated unmetabolized in urine, all within the first 24-hr period following dosing. In contrast to this, a similar dose of FB1 given by gavage resulted in the recovery of only 0.4% of the FB1 in urine.     

Cytotoxicity of fumonisin B(1) in spheroid and monolayer cultures of rat hepatocytes

Fumonisin B(1) (FB(1)), the most prevalent member of toxins produced by several species of Fusarium molds, which occur mainly in maize, causes several fatal hepatopathies and nephropathies of animals. The current study was scrutinized to ascertain different cytotoxic and morphological transformations in rat hepatocytes induced by the treatments of diverse concentrations (300, 500, or 1000 microM) of fumonisin B(1) in vitro, using both monolayer and spheroid cultures. In each hepatocyte culture, the cytotoxicity of FB(1) was augmented in dose- and time-response manners. Morphological transformations among FB(1)-treated groups integrated accumulation of lipid droplets, cytoplasmic vacuolation in hepatocyte monolayers, and bleb formation in the hepatocyte spheroids. Additionally, electron microscopy revealed the loss of microvilli, mitochondrial swelling, and formation of lamellar membranous whorl in the vacuoles and bile canaliculi-like structures. Appearance of electron dense bodies in the monolayers, and loss of cell-to-cell contact in spheroids were depicted in 1000 microM FB(1)-treated hepatocytes. These outcomes insinuate different vital events in explaining morphological transformations in the cell membrane and organelles, induced by fumonisins in rat hepatocytes.     

Application of adsorbent agents technology in the removal of aflatoxin B(1) and fumonisin B(1) from malt extract.

The commercially hydrated sodium calcium aluminosilicate (HSCAS) and the Egyptian montmorillonite (EM) had an excellent capability of adsorbing AFB(1) and FB(1) in an aqueous solution at different tested levels. The adsorption ratio of HSCAS ranged from 95.3% to 99.1% and 84.7% to 92.4% of the available AFB(1) and FB(1) respectively. EM showed an adsorption ratio ranged from 95.4% to 99.2% and 78.2% to 92.2% for AFB(1) and FB(1) respectively. Both adsorbents were effective at 0.5% level. Results of the ability of these adsorbents at level of 0.5% (w/v) to adsorb AFB(1) and FB(1) in malt extract spiked with 50, 100 and 200 ppb indicated that the capability of adsorbing of HSCAS ranged from 98.5% to 98.9% and 88.2% to 91.9% for AFB(1) and FB(1) respectively. Whereas, the capability of adsorbing of EM ranged from 98.1% to 98.7% and 88.2% to 92.5% for AFB(1) and FB(1) respectively.     

Deamination of fumonisin B(1) and biological assessment of reaction product toxicity

Fumonisin B(1), a potent mycotoxin found in grain, has been resistant to degradation and detoxification by a variety of methods, including milling, fermentation, ammoniation, and ozonation. The primary amine of this compound contributes significantly to its toxicity; therefore, the major aim of this research was to remove this moiety via diazotization. In this study, fumonisin B(1) was deaminated in aqueous solution under conditions of acidic pH and low temperature (pH 1.0 and 5 degrees C) with the addition of NaNO(2). The concentration of fumonisin B(1) in the solution was analyzed by HPLC using o-phthaldialdehyde to derivatize the primary amine. Progress of the reaction was monitored as a loss of the derivatized peak as observed by HPLC with fluorescence detection. TLC analysis showed the disappearance of fumonisin B(1) following diazotization. Further, TLC displayed at least four reaction products that were not primary amines. Matrix-assisted laser desorption/ionization mass spectrometry coupled with time-of-flight analysis of the diazotization products also showed a diminished amount of authentic fumonisin B(1) and allowed identification of a product formed by the replacement of the primary amine with a hydroxyl group. The adult Hydra attenuata bioassay indicated a marked decrease in the toxicity of the products in comparison to parent fumonisin B(1). Optimization of this reaction could result in a rapid and practical method for the reclamation of fumonisin B(1)-contaminated feeds.     

Effect of fumonisin B(1) on rat hepatic P450 system

The effects of the mycotoxin fumonisin B(1) (FB(1)) on the hepatic cytochrome P450 system were investigated in male rats dosed daily by oral gavage with 3 mg FB(1) per kg body weight for 9 consecutive days. FB(1) treatment resulted in a reduced weight gain. At the same time, CYP2E activity was increased, which is considered to mark the metabolic changes inherent to growth retardation in young rats. Treatment with FB(1) also resulted in a selective inhibition of CYP2C11 and to a lesser extent, CYP1A2 in liver microsomes obtained from treated animals, whereas it did not affect significantly the activity of CYP2A1/2A2, CYP2B1/2B2, CYP3A1/3A2 and CYP4A. The significant inhibition of CYP2C11 is considered to reflect a suppressed activity of protein kinase activity resulting from the inhibition of sphingolipid biosynthesis caused by FB(1).