Approaches to the risk assessment of fumonisins in corn-based foods in Canada

Mycotoxins in corn-based food products consumed in Brazil: an exposure assessment for fumonisins

Samples from 10 different corn-based food products commercially sold in the Federal District of Brazil were analyzed for fumonisins (FB1 and FB2) using HPLC/fluorescence following naphthalene-2,3 dicarboxaldehyde (NDA) derivatization (limit of quantification (LOQ) = 0.020 mg/kg). Samples were also analyzed for aflatoxins (B1, B2, G1, and G2) on a thin-layer chromatrography (TLC) plate under UV light (LOQ of 2 microg/kg). From the 208 samples analyzed, 80.7 and 71.6% had quantifiable levels of FB1 and FB2, respectively. Mean levels of total fumonisins (FB1 + FB2) ranged from 0.127 mg/kg for corn flakes to 2.04 mg/kg for cornmeal ( creme de milho). No FBs were detected in any of the fresh, sweet corn on the cob samples analyzed. Aflatoxins were not detected in any of the 101 samples analyzed. The daily intakes of fumonisins through the consumption of corn-based food products was estimated using consumption data estimated from the 2002/2003 Brazilian Household Budget Survey and the level of fumonisins found in this and other studies conducted in Brazil. In the Federal District, the calculated total daily intake for the total and the consumers-only populations represented, respectively, 9.0 and 159% of the provisional maximum total daily intake (PMTDI) of 2 microg/kg body weight per day. At the national level, the intakes were calculated based on the fumonisin levels found in the Federal District and on published data from studies conducted elsewhere in the country. They represented 24.1 and 355% PMTDI for the total and the consumers-only populations, respectively. The high incidence of fumonisins in some corn-based products and the exposure levels found for specific subpopulations in the present study indicate the need for setting safe regulatory levels for fumonisins in food in Brazil.

An overview of rodent toxicities: liver and kidney effects of fumonisins and Fusarium moniliforme

Fumonisins are produced by Fusarium moniliforme F. verticillioides) and other Fusarium that grow on corn worldwide. They cause fatal toxicoses of horses and swine. Their effects in humans are unclear, but epidemiologic evidence suggests that consumption of fumonisin-contaminated corn contributes to human esophageal cancer in southern Africa and China. Much has been learned from rodent studies about fumonisin B1(FB1), the most common homologue. FB1 is poorly absorbed and rapidly eliminated in feces. Minor amounts are retained in liver and kidneys. Unlike other mycotoxins, fumonisins cause the same liver cancer promotion and subchronic (studies (3/4) 90 days) liver and kidney effects as (italic)F. moniliforme. FB 1 induces apoptosis of hepatocytes and of proximal tubule epithelial cells. More advanced lesions in both organs are characterized by simultaneous cell loss (apoptosis and necrosis) and proliferation (mitosis). Microscopic and other findings suggest that an imbalance between cell loss and replacement develops, a condition favorable for carcinogenesis. On the molecular level, fumonisins inhibit ceramide synthase, and disrupt sphingolipid metabolism and, theoretically, sphingolipid-mediated regulatory processes that influence apoptosis and mitosis. Liver sphingolipid effects and toxicity are correlated, and ceramide synthase inhibition occurs in liver and kidney at doses below their respective no-observed-effect levels. FB1 does not cross the placenta and is not teratogenic in vivoin rats, mice, or rabbits, but is embryotoxic at high, maternally toxic doses. These data have contributed to preliminary risk evaluation and to protocol development for carcinogenicity and chronic toxicity studies of FB1 in rats and mice.

Determination of fumonisins B1 and B2 in cornflakes by high performance liquid chromatography and immunoaffinity clean-up

The determination of fumonisins in cornflakes is a challenging matter as the actually available methods for the analysis of corn do not perform well when applied to this more complex matrix. After testing several factors that may affect the analytical performance, an accurate method for the determination of fumonisin B1 (FB1) and B2 (FB2) in cornflakes has been developed. The method uses immunoaffinity chromatography for clean-up and high performance liquid chromatography (HPLC) for quantification of the toxins. Samples were extracted twice with acetonitrile-methanol-water (25:25:50) and the combined extracts were diluted with phosphate buffered saline (PBS) and applied to a FumoniTest immunoaffinity column. After washing with PBS, fumonisins were eluted from the column with methanol and reacted with o-phthaldialdehyde/2-mercaptoethanol to form fluorescent derivatives. Fumonisin derivatives were analysed by reversed phase HPLC with fluorometric detection using methanol-0.1 M phosphate buffer (77:23; pH adjusted at 3.35) as mobile phase. The average recoveries for FB1 and FB2 spiked in the ranges of 0.33 2.80 microg/g and 0.17-1.40 microg/g were 102.6% and 95.1%, respectively, with average relative standard deviations of 9% and 8%. The limit of quantification for FB1 and FB2 was 0.005 microg/g based on a signal-to-noise ratio of 6.1 by using a sensitive fluorescence detector. The method was used to analyse 18 cornflakes and cornflake cereals samples/for FB1 and FB2 contamination. All but one sample were found to be contaminated, with maximum FB1 and FB2 concentrations of 1.092 microg/g and 0.235 microg/g, respectively. Mean FB1 and FB2 concentrations were 0.157 microg/(g and 0.036 microg/g, respectively.

Occurrence of fumonisin B1 and B2 in beer

A total of 29 nationally distributed brands of beer, representing 25 domestic US and four imported brands, were purchased in retail outlets in Lincoln, Nebraska and analysed for concentrations of fumonisin B1(FB1) and B2(FB2). Immunoaffinity column extraction and cleanup of fumonisins from the beer samples, coupled with detection and analysis by gradient high performance liquid chromatography (HPLC), provided a limit of quantitation for each toxin of 0.3 ng/ml. Of the brands of beer sampled, 86% were positive for FB1 and 41% were positive for FB2. No beer contained a detectable quantity of FB2 without a detectable quantity of FB1. The total fumonisin (FB1 + FB2) content of positive samples ranged from 0.3 to 12.7 ng/ml, with a mean concentration for all positive samples of 4.0 +/- 3.4 ng/ml (n = 25). Considering that the level of fumonisin contamination of corn in recent harvest years has been minimal, the results of this limited survey could represent levels associated with current agricultural and brewing practices.

A survey of fumonisins, deoxynivalenol, zearalenone and aflatoxins contamination in corn-based food products in Argentina

The presence of mycotoxins in corn-based foods available in Argentina was determined in order to make a preliminary exposure assessment. Thirty-eight samples [corn meal ('polenta') and corn flakes] of different local brands were analysed for zearalenone, deoxynivalenol and aflatoxins by TLC and fumonisins (FB1, FB2 and FB3) by HPLC. None of the 38 samples contained any detectable amount of aflatoxins (< 2 micrograms/kg), zearalenone (< 50 micrograms/kg) and deoxynivalenol (< 50 micrograms/kg). By contrast fumonisin contamination was found in 95% of the samples. The highest fumonisin levels were found in corn meal: FB1 (range positives: 60-2860 micrograms/kg; mean positive value: 556 micrograms/kg), FB2 (61-1090 micrograms/kg; 232 micrograms/kg) and FB3 (18-1015 micrograms/kg; 150 micrograms/kg). Low levels of fumonisin B1 were detected in 16/17 corn flakes samples (2-38 micrograms/kg). Total fumonisin levels in corn meal were more than 1000 micrograms/kg in 24% (5/21) of the samples. Although it is not the staple food in Argentina, maize consumption is very important, especially among children. A daily fumonisin intake of 11.3 micrograms/kg of body weight was estimated for child consumers (1-5 years old) based on an average consumption of 200 g of corn meal/day. Calculated at an average rate for all children (consumers or not) the intake estimate was 0.9 microgram/kg of body weight.

Studies on extraction of fumonisins from rice, corn-based foods and beans

Different solvent mixtures were examined for extraction of fumonisins from various naturally contaminated and spiked foods and foodstuffs: rough rice, retail rice, rice flour, white corn flour, corn meal, corn starch, corn flakes, tortilla/corn chips, white bean flour, white beans, mung beans, adzuki beans and infant cereals. Most of the naturally contaminated samples were analyzed using the extraction solvent mixtures methanol-acetonitrile-water (25:25:50) (solvent A) and methanol-water (75:25 or 80:20) (solvents B, BB); some were extracted with 0.1 M sodium hydrogen phosphate-acetonitrile (1:1, adjusted to pH 3.0 with o-phosphoric acid) (solvent C) and methanol-0.025 M borate buffer (3:1, adjusted to pH 9.2 with 1 N sodium hydroxide) (solvent D). A 1-ml SAX solid phase extraction column was used for the cleanup in all cases except for infant cereals, for which immunoaffinity chromatography was used; fumonisin concentrations were determined by liquid chromatography.Solvent A gave slightly better extraction of fumonisins from one of two samples of naturally contaminated rough rice than solvent B (fumonisin B1: 4080 ng/g versus 3150 ng/g; fumonisin B2:1100 ng/ g versus 922 ng/g) and much better extraction than solvent C (1210 ng/g fumonisin B1 and 315 ng/g fumonisin B2) or solvent D (372 ng/ g fumonisin B1 and 191 ng/g fumonisin B2). However, spike recoveries on a similar rice naturally contaminated at a lower level were only in the 43-53% range (solvent A). Recovery of fumonisins was very poor from spiked white rice flour but satisfactory from other rice foods.Solvent A similarly gave slightly better extraction of fumonisins from a sample of naturally contaminated white corn flour than solvent B (fumonisin B1 1260 ng/g versus 931 ng/g; fumonisin B2: 511 ng/g versus 447 ng/g ) and better extraction than solvents C and D. Solvent A was also a better solvent for extraction of fumonisins from naturally contaminated tortilla chips and infant cereals. Study of naturally contaminated corn starch was confounded by instability of fumonisins in this food. Recovery of fumonisins from spiked corn meal, tortilla chips, corn flakes, various types of beans and infant cereals with solvent A and/or solvent B (or BB) was satisfactory.

Glutathione S-transferase-placental form expression and proliferation of hepatocytes in fumonisin B1-treated male and female Sprague-Dawley rats

Fumonisin B1 (FB1), a mycotoxin produced by a common corn contaminant Fusarium moniliforme and a hepatocarcinogen in rats, has been previously suggested to act as a poor initiator, but a better promoter of gamma-glutamyltranspeptidase (GGT)-positive rat liver preneoplastic lesions. Using glutathione S-transferase-placental form (GSTP) as a more sensitive marker of initiation, we have further evaluated the initiating capacity of various doses of purified FB1 administered (a) intraperitoneally (i.p.) to male Sprague-Dawley (SD) rats for 4 days and (b) orally (PO) to male and female SD rats for 11 days. Compared to their respective controls, significant increases in GSTP-positive hepatocytes were observed in male rats administered FB1 i.p. at 10 mg/kg body weight/day for 4 days, as well as in male and female rats treated with 35 and 75 mg/kg body weight/day FB1 p.o. for 11 days. The percentage section area of liver occupied by GSTP-positive mini-foci comprising of three to 12 cells was increased significantly in male rats given 10 mg/kg FB1 i.p., or in p.o.-treated males and females with 75 mg/kg FB1. Both i.p. and p.o. FB1 treatments resulted in dose-related enhanced hepatocyte proliferation as measured by proliferating cell nuclear antigen (PCNA) labeling with significant increases in the number of PCNA-positive nuclei at the same i.p. and p.o. dose levels where the number of GSTP-positive cells were elevated. In all studies, enhanced PCNA and GSTP expression occurred at FB1 doses which, based on serum biochemical and histopathological data previously reported from our laboratory, were shown to be hepatotoxic. Therefore, our data suggest that in a manner similar to known genotoxic carcinogens, FB1 has the capacity to initiate GSTP-positive hepatocytes with their subsequent development into GSTP mini-foci at exposure levels that induce enhanced hepatocyte proliferation in response to liver toxicity. In SD rats, this occurs as early as within 4 days of i.p. treatment or 11 days of p.o. treatment.

Response of growing swine to dietary exposure to pure fumonisin B1 during an eight-week period: growth and clinical parameters

Consumption of corn or corn-based products contaminated with Fusarium moniliforme/fumonisins has been associated with a variety of animal and human diseases and is a major food/feed safety issue. This study focused on the clinical toxicity and performance parameters in growing swing exposed to low to moderate levels of pure fumonisin B1 (FB.) for 8 weeks. Male (castrated) and female pigs were fed diets containing 0,0.1,1.0, and 10 mg FB1/kg diet (ppm). Weight gains and feed consumption were measured weekly. Blood samples were collected throughout the study, and various clinical and hematological parameters were measured. Because fumonisins are potent inhibitors of sphingolipid biosynthesis, sphinganine and sphingosine concentrations were determined in the liver, lung, and kidney. Organ weights and carcass quality were measured at the end of the trial. In general, male pigs were more adversely affected by FB1 in the diet than females. The average daily gain for males decreased by 8% for pigs fed 1.0 ppm and by 11% at 10.0 ppm, when compared to the control (0 ppm). Males fed 0.1 ppm showed an erratic growth pattern during the first 5 weeks of the experiment. Feed consumption for the same animals was somewhat higher than that of the controls during each of the first 4 weeks but thereafter was 6-7% lower each week as compared to controls. Female pigs fed FB1-diets showed a general enhancement of feed consumption until week 4. Among clinical chemistry parameters, cholesterol increased in males for the 1.0 and 10.0 ppm diets as compared to controls after 2 weeks, while the levels in both sexes were elevated for the 1.0 ppm diet only by the end of the experiment. Serum liver enzyme concentrations were altered during week 2 only. Changes were observed in the weight of the pancreas and adrenals for male pigs fed FB1 diets as compared to controls. The free sphinganine to free sphingosine ratio (biomarker of exposure in FB1-consuming animals) increased in all three organs for the 10 ppm diet, regardless of sex. The study indicated that FB1 can cause different effects at each dose level, at concentrations as low as 0.1 ppm (showing erratic growth) followed by a reduced growth and biochemical abnormalities in blood (1.0 ppm) and sphingolipid alterations in tissues (10.0 ppm). Some of these effects occurred below the exposure level that caused alteration in sphingolipid metabolism.