Distribution and excretion of a single dose of the mycotoxin fumonisin B1 in a non-human primate

An update on genotoxic and epigenetic studies of fumonisin B1

Fumonisins (FBs), a widespread group of mycotoxins produced by Fusarium spp., are natural contaminants in cereals and foodstuffs. Fumonisin B1 (FB1) is the most toxic and prevalent mycotoxin of this group, and it has been reported that FB1 accounts for 70-80% of FBs produced by the mycotoxigenic strains. The mode of action of FB1 depends on the structural similarity with sphinganine/sphingosine N-acyltransferase. This fact causes an accumulation of sphingoid bases and blocks the sphingolipid biosynthesis or the function of sphingolipids. Diverse toxic effects and diseases such as hepatocarcinogenicity, hepatotoxicity, nephrotoxicity, and cytotoxicity have been reported, and diseases like leukoencephalomalacia in horses and pulmonary oedema in horses and swine have been described. In humans, FBs have been associated with oesophageal cancer, liver cancer, neural tube defects, and infantile growth delay. However, despite the International Agency for Research on Cancer designated FB1 as a possibly carcinogenic to humans, its genotoxicity and epigenetic properties have not been clearly elucidated. This review aims to summarise the progress in research about the genotoxic and epigenetics effects of FB1.

Development and Limitations of Exposure Biomarkers to Dietary Contaminants Mycotoxins

Mycotoxins are toxic secondary fungal metabolites that frequently contaminate cereal crops globally, presenting exposure hazards to humans and livestock in many settings. The heterogeneous distribution of mycotoxins in food restricts the usefulness of food sampling and intake estimates for epidemiological studies, making validated exposure biomarkers better tools for informing epidemiological investigations. While biomarkers of exposure have served important roles for understanding the public health impact of mycotoxins such as aflatoxins (AF), the science of biomarkers must continue advancing to allow for better understanding of mycotoxins' roles in the etiology of disease and the effectiveness of mitigation strategies. This review will discuss mycotoxin biomarker development approaches over several decades for four toxins of significant public health concerns, AFs, fumonisins (FB), deoxynivalenol (DON), and ochratoxin A (OTA). This review will also highlight some knowledge gaps, key needs and potential pitfalls in mycotoxin biomarker interpretation.

Molecular toxicology and carcinogenesis of fumonisins: a review

Fumonisins, discovered in 1988 are a group of naturally occurring toxins produced by fusarium pathogenic fungi. Besides their presence in animal feeds, contamination of human foods such as corn, millet, oats, rye, barley, wheat and their products are widespread. Exposure to fumonisins results in species and organ specific toxicities including neurological disorders among equids, pulmonary edema in swine, esophageal cancer in humans and both kidney and liver related toxicities in rodents. This review seeks to consolidate groundbreaking research on the science of fumonisins toxicity, highlight recent progress on fumonisins research, and provide an overview of plausible mechanistic biomarkers for fumonisins exposure assessment.

Detection of Mycotoxins in Food Using Surface-Enhanced Raman Spectroscopy: A Review

Mycotoxins are toxic metabolites produced by fungi that contaminate many important crops worldwide. Humans are commonly exposed to mycotoxins through the consumption of contaminated food products. Mycotoxin contamination is unpredictable and unavoidable; it occurs at any point in the food production system under favorable conditions, and they cannot be destroyed by common heat treatments, because of their high thermal stability. Early and fast detection plays an essential role in this unique challenge to monitor the presence of these compounds in the food chain. Surface-enhanced Raman spectroscopy (SERS) is an advanced spectroscopic technique that integrates Raman spectroscopic molecular fingerprinting and enhanced sensitivity based on nanotechnology to meet the requirement of sensitivity and selectivity, but that can also be performed in a cost-effective and straightforward manner. This Review focuses on the SERS methodologies applied to date for qualitative and quantitative analysis of mycotoxins based on a variety of SERS substrates, as well as our perspectives on current limitations and future trends for applying this technique to mycotoxin analyses.

Possible Role of Phosphatidylcholine and Sphingomyelin on Fumonisin B1-mediated Toxicity

A major corn-related mycotoxin, fumonisin B1 (FB1), continues to attract attention of researchers as well as risk-assessors due to the diverse toxicological characteristics, including distinct target tissues in different animal species and opposite susceptibility in males and females in mice and rats. More than thirty years passed since the structure identification as a sphingoid-like chemical, but the causal mechanism of the toxicity remains obscure in spites of extensive studies. Considerable amounts of knowledge have been accumulated on the biochemical/toxicological actions of FB1, but the influence on lipid dynamics and mobilization in the body has not been focused well in relation to the FB1-mediated toxicity. Considerable influences of this toxin on mobilization of sphingolipids and phospholipids and also on adaptive changes in their compositions in tissues are implicated from recent studies on FB1-interacting ceramide synthases. Accumulated patho-physiological data also suggest a possible role of hepatic phospholipid on FB1-mediated toxicity. Thus, a mechanism of FB1-mediated toxicity is discussed in relation to the mobilization of phospholipids and sphingolipids in the body in this context.

A prospective study of growth and biomarkers of exposure to aflatoxin and fumonisin during early childhood in Tanzania

BACKGROUND

Aflatoxin and fumonisin are toxic food contaminants. Knowledge about effects of their exposure and coexposure on child growth is inadequate.

OBJECTIVE

We investigated the association between child growth and aflatoxin and fumonisin exposure in Tanzania.

METHODS

A total of 166 children were recruited at 6-14 months of age and studied at recruitment, and at the 6th and 12th month following recruitment. Blood and urine samples were collected and analyzed for plasma aflatoxin-albumin adducts (AF-alb) using ELISA, and urinary fumonisin B1 (UFB1) using liquid chromatography-mass spectrometry, respectively. Anthropometric measurements were taken, and growth index z-scores were computed.

RESULTS

AF-alb geometric mean concentrations (95% CIs) were 4.7 (3.9, 5.6), 12.9 (9.9, 16.7), and 23.5 (19.9, 27.7) pg/mg albumin at recruitment, 6 months, and 12 months from recruitment, respectively. At these respective sampling times, geometric mean UFB1 concentrations (95% CI) were 313.9 (257.4, 382.9), 167.3 (135.4, 206.7), and 569.5 (464.5, 698.2) pg/mL urine, and the prevalence of stunted children was 44%, 55%, and 56%, respectively. UFB1 concentrations at recruitment were negatively associated with length-for-age z-scores (LAZ) at 6 months (p = 0.016) and at 12 months from recruitment (p = 0.014). The mean UFB1 of the three sampling times (at recruitment and at 6 and 12 months from recruitment) in each child was negatively associated with LAZ (p < 0.001) and length velocity (p = 0.004) at 12 months from recruitment. The negative association between AF-alb and child growth did not reach statistical significance.

CONCLUSIONS

Exposure to fumonisin alone or coexposure with aflatoxins may contribute to child growth impairment.

In vivo formation of N-acyl-fumonisin B1

Fumonisins are fungal toxins found in corn and in corn-based foods. Fumonisin B1 (FB1) is the most common and is toxic to animals, causes cancer in rodents, and is a suspected risk factor for cancer and birth defects in humans. The hydrolyzed form of FB1 (HFB1) also occurs in foods and is metabolized by rats to compounds collectively known as N-acyl-HFB1 (also known as N-acyl-AP1). N-acyl-HFB1 is structurally similar to ceramides, metabolites which have important structural and signaling functions in cells. FB1 is N-acylated in vitro to ceramide-like metabolites which, like FB1, are cytotoxic. However, metabolism of FB1 and inhibition of ceramide synthase by its metabolites in vivo has not been demonstrated. Male rats were dosed ip with 0.5, 1, or 2 mg/kg body weight FB1 on five consecutive days and the liver and kidney thereafter processed for chemical analysis. N-acyl derivatives of fumonisin B1 were identified for the first time in these principal target organs of FB1 in rats, at levels up to 0.4 nmol/g tissue using mass spectrometry. The N-acyl chain length of the metabolites varied in a tissue-dependent manner with C16 derivatives predominating in the kidney and C24 derivatives being prevalent in the liver. The toxicological significance of N-acyl-fumonisins is not known and warrants investigation.

Toxic mechanisms induced by fumonisin b1 mycotoxin on human intestinal cell line

The gastrointestinal tract is the main target of exposure to mycotoxin fumonisin B1 (FB1), common natural contaminant in food. Previous studies reported that proliferating cells are more sensitive than confluent cells to the toxic effect of FB1. This study aims to investigate, by dose- and time-dependent experiments on human colon proliferating intestinal cell line (HT-29), the modifications induced by FB1 at concentrations ranging from 0.25 to 69 μM. The choice of highest FB1 concentration considered the low toxicity previously reported on intestinal cell lines, whereas the lowest one corresponded to the lower FBs levels permitted by European Commission Regulation. Different functional parameters were tested such as cell proliferation, oxidative status, immunomodulatory effect and changes in membrane microviscosity. In addition FB1-FITC localization in this cell line was assessed by using confocal laser scanning microscopy. Lipid peroxidation induction was the main and early (12 h) effect induced by FB1 at concentrations ranging from 0.5 to 69 μM, followed by inhibition of cell proliferation (up to 8.6 μM), the immunomodulatory effect (up to 17.2 μM), by assessing IL-8 secretion, and increase in membrane microviscosity (up to 34.5 μM). The toxic effects observed in different functional parameters were not dose-dependent and could be the consequence of the FB1 intracytoplasmatic localization as confirmed by confocal microscopy results. The different timescales and concentrations active of different functional parameters could suggest different cellular targets of FB1.

Multiple mycotoxin exposure determined by urinary biomarkers in rural subsistence farmers in the former Transkei, South Africa

Subsistence farmers are exposed to a range of mycotoxins. This study applied novel urinary multi-mycotoxin LC-MS/MS methods to determine multiple exposure biomarkers in the high oesophageal cancer region, Transkei, South Africa. Fifty-three female participants donated part of their maize-based evening meal and first void morning urine, which was analysed both with sample clean-up (single and multi-biomarker) and by a 'dilute-and-shoot' multi-biomarker method. Results were corrected for recovery with LOD for not detected. A single biomarker method detected fumonisin B1 (FB1) (87% incidence; mean±standard deviation 0.342±0.466 ng/mg creatinine) and deoxynivalenol (100%; mean 20.4±49.4 ng/mg creatinine) after hydrolysis with β-glucuronidase. The multi-biomarker 'dilute-and-shoot' method indicated deoxynivalenol-15-glucuronide was predominantly present. A multi-biomarker method with β-glucuronidase and immunoaffinity clean-up determined zearalenone (100%; 0.529±1.60 ng/mg creatinine), FB1 (96%; 1.52±2.17 ng/mg creatinine), α-zearalenol (92%; 0.614±1.91 ng/mg creatinine), deoxynivalenol (87%; 11.3±27.1 ng/mg creatinine), β-zearalenol (75%; 0.702±2.95 ng/mg creatinine) and ochratoxin A (98%; 0.041±0.086 ng/mg creatinine). These demonstrate the value of multi-biomarker methods in measuring exposures in populations exposed to multiple mycotoxins. This is the first finding of urinary deoxynivalenol, zearalenone, their conjugates, ochratoxin A and zearalenols in Transkei.

Fumonisin biomarkers in maize eaters and implications for human disease

Maize is the predominant food source contaminated by fumonisins and this has particular health risks for communities consuming maize as a staple diet. The main biochemical effect of fumonisins is the inhibition of ceramide biosynthesis causing an increase in sphingoid bases and sphingoid base 1-phosphates and a depletion of the complex sphingolipids, thereby disrupting lipid metabolism and sphingolipid-mediated processes and signalling systems. Attempts to use the elevation of sphinganine as a human biomarker of fumonisin exposure have to date been unsuccessful. Consequently, recent research has focussed on developing a urinary exposure biomarker based on the measurement of the nonmetabolised toxin. In animals, fumonisins are poorly absorbed in the gut and are mostly excreted unmetabolised in faeces, with only a small percentage (0.25-2.0%) in urine. This appears to also be true in humans were fumonisin B1 (FB1) is detectable in urine soon after exposure, but in very small amounts relative to total intake. However, with modern sensitive and selective analytical methods such as liquid chromatography-tandem mass spectrometry, these low levels can be readily determined. The first study to show a positive correlation between consumption of maize and urinary FB1 was conducted in a Mexican population consuming tortillas as a staple food. Further validation of this relationship was achieved in a South African subsistence farming community with a positive correlation between urinary FB1 and fumonisin exposure, as assessed by food analysis and food intake data. The most recent developments are aimed at measuring multiple mycotoxin biomarkers in urine, including FB1. Current exposure studies in Guatemala are combining the urinary biomarker with measurement of sphinganine-1-phosphate in blood spots as a measure of biochemical effect. Thus, the urinary FB1 biomarker could contribute considerably in assessing the adverse health impact of fumonisin exposure.

Effect ofin vitro digestion on fumonisin B1 in corn flakes

Low levels of fumonisins have been found frequently in corn based breakfast cereals and can occur bound to protein and other matrix components.In vitro digestion of two samples of corn flakes was carried out under "fed conditions." Fumonisins were measured as o-phthaldialdehyde/mercaptoethanol derivatives by LC-fluorescence. One sample of corn flakes (FN12) had high concentrations of fumonisin B1 (FB) (average 125 ng/g) and total bound FB1, (TB FB1) (average 92 ng/g) and the other (FN11) had a low level of free FB1 (average 29 ng/g) and no detectable TB FB1. After incubation of the samples with gastrointestinal tract solutions simulating saliva plus stomach and duodenal juices, chyme was analysed for FB1, hydrolyzed FB1 (HFB1) and partially hydrolyzed fumonisin B1 (PHFB1). The bioaccessibility (percentage of FB1 released from corn flakes into chyme) was 38-78% for incurred FB1 in FN12, 8-54% for incurred plus spiked FB1 in FN12, and 19-66% for incurred plus spiked FB1 in FN11. HFB1 and PHFB1 were not detected. If free FB1 was first extracted from sample FN12, no FB1 was detected in the chyme, indicating no contribution from TB FB1. Concentrations were corrected for method recovery of FB1 or, for bound FB1, partial method recovery of HFB1.

The role of biomarkers in evaluating human health concerns from fungal contaminants in food

Mycotoxins are toxic secondary metabolites that globally contaminate an estimated 25 % of cereal crops and thus exposure is frequent in many populations. Aflatoxins, fumonisins and deoxynivalenol are amongst those mycotoxins of particular concern from a human health perspective. A number of risks to health are suggested including cancer, growth faltering, immune suppression and neural tube defects; though only the demonstrated role for aflatoxin in the aetiology of liver cancer is widely recognised. The heterogeneous distribution of mycotoxins in food restricts the usefulness of food sampling and intake estimates; instead biomarkers provide better tools for informing epidemiological investigations. Validated exposure biomarkers for aflatoxin (urinary aflatoxin M(1), aflatoxin-N7-guaunine, serum aflatoxin-albumin) were established almost 20 years ago and were critical in confirming aflatoxins as potent liver carcinogens. Validation has included demonstration of assay robustness, intake v. biomarker level, and stability of stored samples. More recently, aflatoxin exposure biomarkers are revealing concerns of growth faltering and immune suppression; importantly, they are being used to assess the effectiveness of intervention strategies. For fumonisins and deoxynivalenol these steps of development and validation have significantly advanced in recent years. Such biomarkers should better inform epidemiological studies and thus improve our understanding of their potential risk to human health.

Calcium montmorillonite clay reduces urinary biomarkers of fumonisin B₁ exposure in rats and humans

Fumonisin B₁ (FB₁) is often a co-contaminant with aflatoxin (AF) in grains and may enhance AF's carcinogenicity by acting as a cancer promoter. Calcium montmorillonite (i.e. NovaSil, NS) is a possible dietary intervention to help decrease chronic aflatoxin exposure where populations are at risk. Previous studies show that an oral dose of NS clay was able to reduce AF exposure in a Ghanaian population. In vitro analyses from our laboratory indicated that FB₁ (like aflatoxin) could also be sorbed onto the surfaces of NS. Hence, our objectives were to evaluate the efficacy of NS clay to reduce urinary FB₁ in a rodent model and then in a human population highly exposed to AF. In the rodent model, male Fisher rats were randomly assigned to either FB₁ control, FB₁ + 2% NS or absolute control group. FB₁ alone or with clay was given as a single dose by gavage. For the human trial, participants received NS (1.5 or 3 g day⁻¹) or placebo (1.5 g day⁻¹) for 3 months. Urines from weeks 8 and 10 were collected from the study participants for analysis. In rats, NS significantly reduced urinary FB₁ biomarker by 20% in 24 h and 50% after 48 h compared to controls. In the humans, 56% of the urine samples analysed (n = 186) had detectable levels of FB₁. Median urinary FB₁ levels were significantly (p < 0.05) decreased by >90% in the high dose NS group (3 g day⁻¹) compared to the placebo. This work indicates that our study participants in Ghana were exposed to FB₁ (in addition to AFs) from the diet. Moreover, earlier studies have shown conclusively that NS reduces the bioavailability of AF and the findings from this study suggest that NS clay also reduces the bioavailability FB₁. This is important since AF is a proven dietary risk factor for hepatocellular carcinoma (HCC) in humans and FB₁ is suspected to be a dietary risk factor for HCC and oesophageal cancer in humans.

Quantitative determination of mycotoxins in urine by LC-MS/MS

Naturally occurring mycotoxins are responsible for a wide array of adverse health effects. The measurement of urinary mycotoxin levels is a useful means of assessing an individual's exposure, but the development of sensitive and accurate analytical methods for detecting mycotoxins and their metabolites in urine samples is challenging. Urinary mycotoxins are present in low pg ml⁻¹ concentrations, and the chromatographic identification of their metabolites can be obscured by other endogenous metabolites. We developed an analytical method focused on the selection of two appropriate multiple-reaction monitoring transition for unambiguous identification and quantification of carcinogenic aflatoxin M₁ (AFM₁), ochratoxin A (OTA) and fumonisin B₁, B₂ (FB₁, FB₂) in urine samples from a small volunteer group in a pilot study. AFM₁, OTA, FB₁ and FB₂ were concentrated selectively, interfering substances were removed using an immunoaffinity column (IAC), and mycotoxins were measured using liquid chromatography-tandem mass spectrometry (LC-MS/MS) in combination with a stable-isotope standard-dilution assay (SIDA). The method was sensitive enough to measure mycotoxins and their metabolites at pg ml⁻¹ levels in urine. The combination of LC-MS/MS and SIDA was critical to distinguishing pseudo-OTα interference from genuine OTα. Twelve urine samples contained OTA ranging from 0.013 to 0.093 ng ml⁻¹ (mean = 0.031 ng ml⁻¹). AFM₁ were detected in one sample at a 0.002 ng ml⁻¹ level, while FB₁ and FB₂ were undetectable in all 12 samples. None of the samples in this pilot study contained a detectable level of OTα, despite the presence of OTA, and this may suggest the need for further epidemiological investigation of OTA exposure in the Korean population.

Fumonisin B1 as a urinary biomarker of exposure in a maize intervention study among South African subsistence farmers

BACKGROUND

The consumption of maize highly contaminated with carcinogenic fumonisins has been linked to high oesophageal cancer rates. The aim of this study was to validate a urinary fumonisin B1 (UFB1) biomarker as a measure of fumonisin exposure and to investigate the reduction in exposure following a simple and culturally acceptable intervention.

METHODS

At baseline home-grown maize, maize-based porridge, and first-void urine samples were collected from female participants (n=22), following their traditional food practices in Centane, South Africa. During intervention the participants were trained to recognize and remove visibly infected kernels, and to wash the remaining kernels. Participants consumed the porridge prepared from the sorted and washed maize on each day of the two-day intervention. Porridge, maize, and urine samples were collected for FB1 analyses.

RESULTS

The geometric mean (95% confidence interval) for FB1 exposure based on porridge (dry weight) consumption at baseline and following intervention was 4.84 (2.87-8.14) and 1.87 (1.40-2.51) μg FB1/kg body weight/day, respectively, (62% reduction, P<0.05). UFB1C, UFB1 normalized for creatinine, was reduced from 470 (295-750) at baseline to 279 (202-386) pg/mg creatinine following intervention (41% reduction, P=0.06). The UFB1C biomarker was positively correlated with FB1 intake at the individual level (r=0.4972, P<0.01). Urinary excretion of FB1 was estimated to be 0.075% (0.054%-0.104%) of the FB1 intake.

CONCLUSION

UFB1 reflects individual FB1 exposure and thus represents a valuable biomarker for future fumonisin risk assessment.

IMPACT

The simple intervention method, hand sorting and washing, could positively impact on food safety and health in communities exposed to fumonisins.

Biomonitoring of Fusarium spp. Mycotoxins: Perspectives for an Individual Exposure Assessment Tool

Fusarium species are probably the most prevalent toxin-producing fungi of the northern temperate regions and are commonly found on cereals grown in the temperate regions of America, Europe and Asia. Among the toxins formed by Fusarium we find trichothecenes of the A-type or B-type, zearalenone, fumonisins or nivalenol. The current exposure assessment consists of the qualitative and/or quantitative evaluation based on the knowledge of the mycotoxin occurrence in the food and the dietary habits of the population. This process permits quantifying the mycotoxin dietary intake through deterministic or probabilistic methods. Although these methods are suitable to assess the exposure of populations to contaminants and to identify risk groups, they are not recommended to evaluate the individual exposition, due to a low accuracy and sensitivity. On the contrary, the use of biochemical indicators has been proposed as a suitable method to assess individual exposure to contaminants. In this work, several techniques to biomonitor the exposure to fumonisins, deoxynivalenol, zearalenone or T-2 toxin have been reviewed.

The African Fusarium/maize disease

There is a general but rather vague feeling that the use of maize (corn) as a staple foodstuff by black rural Africans is somehow a factor in, or is linked to, chronic disease found in these populations. An attempt is made in this review to consider the evidence for this connection and to identify what is actually the root of the problem. The main thrust of the argument to explain this perception is that maize is routinely contaminated with fungi and of these Fusarium verticillioides is found in maize throughout the world. Evidence is presented to this effect and, further, of the mycotoxins found in maize, the fumonisins are the most common and at the highest levels. Various animal chronic diseases arising from the consumption of contaminated maize are reviewed and possible human conditions listed, in some cases related to the known animal ones. A brief overview of the complicated cellular mechanisms of fumonisin B1 is given and it is concluded that the prime suspect in what might be called "the maize disease" can be attributed to the ingestion of this mycotoxin, sometimes in combination with other synergist mycotoxins and other disease factors, such as smoking and drinking.

Toxicokinetics of fumonisin B1 in turkey poults and tissue persistence after exposure to a diet containing the maximum European tolerance for fumonisins in avian feeds

The kinetic of fumonisin B1 (FB1) after a single IV and oral dose, and FB1 persistence in tissue were investigated in turkey poults by HPLC after purification of samples on columns. After IV administration (single-dose: 10mg FB1/kg bw), serum concentration-time curves were best described by a three-compartment open model. Elimination half-life and mean residence time of FB1 were 85 and 52min, respectively. After oral administration (single-dose: 100mg FB1/kg bw) bioavailability was 3.2%; elimination half-life and mean residence time were 214 and 408min, respectively. Clearance of FB1 was 7.6 and 7.5ml/min/kg for IV and oral administration, respectively. Twenty-four hours after the administration of FB1 by the intravenous route, liver and kidney contained the highest levels of FB1 in tissues, level in muscle was low or below the limit of detection (LD, 13microg/kg). The persistence of FB1 in tissue was also studied after administration for 9 weeks of a feed that contained 5, 10 and 20mg FB1+FB2/kg diet. Eight hours after the last intake of 20mg FB1+FB2/kg feed (maximum recommended concentration of fumonisins established by the EU for avian feed), hepatic and renal FB1 concentrations were 119 and 22microg/kg, level in muscles was below the LD.

Association between tortilla consumption and human urinary fumonisin B1 levels in a Mexican population

Fumonisins are mycotoxins produced by Fusarium spp. and commonly contaminate maize and maize products worldwide. Fumonisins are rodent carcinogens and have been associated with human esophageal cancer. However, the lack of a valid exposure biomarker has hindered both the assessment of human exposure and the evaluation of disease risk. A sensitive liquid chromatography-mass spectrometry method to measure urinary fumonisin B1 (FB1) following extraction on Oasis MAX cartridges was established and applied to urine samples from women in a cohort recruited in Morelos County, Mexico. Urinary FB1 was compared with dietary information on tortilla consumption. FB1 recovery in spiked samples averaged 94% as judged by deuterium-labeled FB1 internal standard. Urinary FB1 was determined in 75 samples from women selected based on low, medium, or high consumption of maize-based tortillas. The geometric mean (95% confidence interval) of urinary FB1 was 35.0 (18.8-65.2), 63.1 (36.8-108.2), and 147.4 (87.6-248.0) pg/mL and the frequency of samples above the detection limit (set at 20 pg FB1/mL urine) was 45%, 80%, and 96% for the low, medium, and high groups, respectively. Women with high intake had a 3-fold higher average FB1 levels compared with the "low intake" group (F = 7.3; P = 0.0015). Urinary FB1 was correlated with maize intake (P(trend) = 0.001); the correlation remained significant after adjusting for age, education, and place of residence. This study suggests that measurement of urinary FB1 is sufficiently sensitive for fumonisin exposure assessment in human populations and could be a valuable tool in investigating the associated health effects of exposure.

Determination of Fumonisin B1 in animal tissues with immunoaffinity purification

Immunoaffinity extraction combined with high-performance liquid chromatography (HPLC) with fluorescence detection was developed to determine Fumonisin B1 (FB1) in duck tissues. The method was linear over a concentration range of 0.013-0.250 microg of FB1/g of liver, kidney and muscle. The limit of quantification was 0.013 microg FB1/g in tissue. The mean percentage of extraction was 75% for liver and kidney and 53% for muscle. This method can be used in duck for the detection of FB1 contamination after exposure, the liver being the most contaminated tissue.

Biomarkers of exposure to fumonisin mycotoxins: a review

The investigation of adverse health effects associated with fungal mycotoxins requires the measurement of human exposure. Most frequently, this exposure is estimated from contamination levels of raw foodstuffs, which are the primary source of toxin exposure, and data on food consumption patterns. However, variations in food preparation methods, food intake, contamination level, intestinal absorption, toxin distribution and excretion lead to individual variations in toxin exposure that are more readily measured with a biomarker. Fumonisin biomarkers have been sought in the measurement of levels of the toxin in physiological samples such as serum, urine, faeces, hair and nails. However, due to the low bioavailability of fumonisin, these samples pose a variety of analytical challenges and also still require validation as biomarkers. The most widely researched fumonisin biomarkers have been those related to the disruption of de novo sphingolipid biosynthesis, namely elevated levels of the sphingoid base, sphinganine, or of its ratio with sphingosine. Elevation of these parameters in humans would potentially provide a biomarker of biochemical effect. A number of investigations into the possible elevation of sphinganine (or its ratio with sphingosine) in human blood and urine have generally failed to correlate with estimates of fumonisin exposure. The sphingoid bases occur naturally in human blood and urine such that their levels have normal ranges, which can be influenced by dietary factors other than fumonisin ingestion. The lower exposures from human diets, as compared with doses in experimental animals, have made detection of changes in these sphingoid biomarkers problematic.

Hydrolyzed fumonisins HFB1 and HFB2 are acylated in vitro and in vivo by ceramide synthase to form cytotoxic N-acyl-metabolites

Fumonisins B1 and B2 (FB1 and FB2) are the most abundant members of the fumonisins--mycotoxins that are produced by Fusarium verticillioides and are natural inhibitors of ceramide synthase. Their hydrolyzed forms, HFB1 and HFB2 (also called AP1 and AP2) are found in some foods, and they are not only inhibitors of ceramide synthase but also undergo acylation by this enzyme. This study characterized the conversion of HFB1 and HFB2 by ceramide synthase to their respective N-acylated metabolites using rat liver microsomes and palmitoyl-CoA or nervonoyl-CoA as cosubstrates, and examined animals that had been dosed with hydrolyzed fumonisins to ascertain if acylation occurs in vivo. Using an HPLC-MS/MS method that allowed the sensitive and selective detection of the acylation products, both HFB1 and HFB2 were found to be metabolized in vitro to nervonoyl- or palmitoyl-HFB1 and -HFB2 (i.e. C24:1-HFB1/2 and C16-HFB1/2, respectively). The apparent vmax was considerably higher for formation of C24:1HFB1 (157 pmol/min/mg protein) than for formation of C16HFB1 (8.7 pmol/min/mg protein). The acylation products also inhibited ceramide synthase and significantly reduced the number of viable cells in an in vitro [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT)] assay using a human colonic cell line (HT29). Furthermore, HPLC-MS/MS analysis of tissues from rats given intraperitoneal doses of HFB1 confirmed that formation of N-acyl-HFB1 occurs in vivo to produce metabolites with fatty acids of various chain lengths. The contribution of acylated HFB1 and HFB2 metabolites to fumonisin toxicity in vivo warrants further investigation.

Validation of fumonisin biomarkers in F344 rats

Fumonisins (FNs) are ubiquitous contaminants of cereal grains. Fumonisin B(1) (FB(1)) was linked to several animal and human diseases. To validate FB(1) biomarkers for studying human disease risks, F344 rats were administered by gavage with either a single dose of 0, 10 or 25 mg FB(1)/kg body weight (BW) or repeated doses of 0, 1.0, or 2.5 mg FB(1)/kg BW/day for 5 weeks. FB(1) excretion and FB(1)-induced metabolic alterations of sphingolipids in rat urine, feces and serum were assessed. Dose-dependent urinary and fecal excretion of free FB(1) were found in both single-dose- and repeat-dose-treated rats. In the single-dose study, urinary sphinganine (Sa) to sphingosine (So) ratio (Sa/So) reached a maximum at day 7 for the high-dose group and at day 5 for the low-dose group, whereas serum Sa/So showed only marginal changes. In the repeat-dose study, urinary Sa/So was persistently elevated at 2 weeks, while serum Sa/So was unchanged. Time course changes of sphinganine 1-phosphate (SaP) and sphingosine 1-phosphate (SoP) were also examined. Although serum Sa/So and SaP/SoP ratios showed no signs of time- or dose-dependent changes, a 10-fold increase in urinary SaP/SoP was observed, suggesting that urinary SaP/SoP is a more sensitive biomarker for FB(1) exposure. The accumulation of SaP and SoP was evident in the time course of SaP/Sa and SoP/So, which may reflect activity changes of enzymes closely related to the metabolism and catabolism of SaP and SoP. These results provide concrete evidence towards the practical use of excreted FB(1), Sa/So and SaP/SoP as biomarkers of exposure to FNs.

Synergistic effects of fumonisin B1 and ochratoxin A: are in vitro cytotoxicity data predictive of in vivo acute toxicity?

Contamination of food and feeds by mycotoxins is a major problem of human and animals health concern which is also extremely detrimental to economy. Mycotoxins producing moulds may produce a diversity of toxins such as aflatoxins, ochratoxins, trichothecenes, zearalenone, fumonisins, tremorgenic toxins and ergot alkaloids. Although toxicological, environmental and epidemiological studies have addressed the problem of these toxins one by one, more than one mycotoxin are found usually in the same contaminated commodities. That rises the incommensurable problem of multi-toxicosis in which the respective metabolites are also involved. These mycotoxins bear potential toxicity leading to acute and chronic effects in humans and animals, depending on species. The mechanisms that lead to toxic effects, such as immune toxicity, and carcinogenicity are complexe. The risk assessment for humans potentially exposed to multi-mycotoxins suffers very much from the lack of adequate food consumption data. Furthermore, for a given mycotoxin synergism and antagonism with other mycotoxins found in the same food commodities are not taken into account. The case of combination of ochratoxin A (OTA) and fumonisin B1 (FB1) has been addressed in the present paper with the purpose of predicting the in vivo toxicity using a simple in vitro test, i.e. neutral red uptake, in three different cell-lines, C6 glioma cells, Caco-2 cells and Vero cells. Using the equation of [ATLA 27 (1999) 957], in vivo toxicity (LD50) is in adequation with the in vitro data, (IC50 values) for both toxins as well as for the combination of 10 microM OTA and variable concentrations of FB1 (10-50 microM). A synergistic effect is prouved in vitro that is in line with some in vivo data from the literature. Such simple in vitro test may thus help predicting in vivo toxicity of combinations of mycotoxins naturally occurring in foodstuffs.

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.

Tissue sphinganine as a biomarker of fumonisin-induced apoptosis

NCTR measured sphinganine concentrations in the livers of mice and in the livers and kidneys of rats in conjunction with a tumour bioassay. In our model of the tumour incidence, target-tissue levels of sphinganine serve as a biomarker for a dose response of fumonisin B1 on cell death. Initially we questioned the utility of sphinganine levels in this role because they were highly variable when compared across time points. In spite of this concern, a conceptual framework and data are presented that support the use of sphinganine as a biomarker for a dose response of fumonisin B1 on cell death. This framework is reasonably consistent with observed sphinganine concentrations in the examined tissues, the literature on fumonisin's effects on sphingolipid synthesis, and our hypothesized mechanism through which fumonisin B1 increases age-specific tumour incidence.

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.

Biochemical and morphological effects of fumonisin B(1) on primary cultures of rat cerebrum

Chronic dietary consumption of the mycotoxin fumonisin B(1) (FB(1)) is associated with leukoencephalomalacia and neuronal degeneration, but identification of the cellular mechanisms underlying this neurotoxicity is difficult due to concurrent adverse systemic changes. For this reason, the present investigation used an in vitro approach to assess the short-term consequences of direct FB(1) (0. 5-75 microM) exposure on astrocytes and oligodendrocytes in primary cultures of rat cerebrum. Beginning at 5 days in vitro, the cultures were exposed to FB(1) at five concentrations (0.5-75 microM), and the cultures were evaluated at 10 and 15 days in vitro. The levels of the sphingolipid-associated constituents sphingosine and sphinganine were determined with a high-performance liquid chromatography. Relative to untreated cultures, exposure to FB(1) diminished the levels of sphingosine at 15 days in vitro, whereas FB(1)-exposed cultures showed significantly increased sphinganine levels and sphinganine/sphingosine ratios. In addition to these changes in sphingolipid constituents, FB(1)-exposed (0.5-75 microM) cultures exhibited a two-fold increase in the number of process-bearing cells by 15 days in vitro. Also, the activity of 2', 3'-cyclic nucleotide 3'-phosphohydrolase, an enzyme associated with myelin and oligodendrocytes, was increased in FB(1)-treated cultures. This study suggests that short-term exposure to FB(1) may modify the proliferation or differentiation of glial cells.

Sphinganine/sphingosine ratio in plasma and urine as a possible biomarker for fumonisin exposure in humans in rural areas of Africa

This study was conducted in the Transkei region of the Eastern Cape and KwaZulu-Natal province, South Africa and in the Bomet district, western Kenya. The sphinganine (Sa)/sphingosine (So) ratios in the plasma and urine of male and female volunteers consuming a staple diet of home-grown maize in Transkei, were 0.34 +/- 0.36 (mean +/- standard deviation) (n = 154) and 0.41 +/- 0.72 (n = 153), respectively and in plasma samples from KwaZulu-Natal it was 0.44 +/- 0.23 (n = 26). In Kenya, the ratios in plasma and urine were 0.28 +/- 0.07 (n = 29) and 0.34 +/- 0.20 (n = 27), respectively. Mean total fumonisin level in home-grown maize, randomly collected in Transkei from the same region where the human volunteers lived, was 580 ng/g (n = 40), as compared to the KwaZulu-Natal province, where no fumonisin (n = 17) were detected (< 10 ng/g) in the home-grown maize. In Kenya, only one of seven samples was contaminated with 60 ng/g fumonisins. No significant differences were found in the Sa/So ratios between males and females within the regions nor between the different regions (P > 0.05). It is possible that the ratio is not sensitive enough to act as a biomarker for fumonisin exposure in humans at these levels of contamination in maize. This is the first report on Sa/So ratios determined in rural populations in Africa consuming home-grown maize as their staple diet.

Elimination and excretion of a single dose of the mycotoxin fumonisin B2 in a non-human primate

The mycotoxin fumonisin B2 (FB2), which can be present at significant levels in maize infected with the fungus Fusarium moniliforme, was dosed both iv and by gavage to vervet monkeys. It was rapidly eliminated from the plasma of vervet monkeys dosed i.v. with 2 mg FB2/kg body mass. The concentration of FB2 in plasma after the iv dose was characterized by an initial distributional phase and a subsequent elimination phase with a mean half-life of 18 min. When two monkeys were dosed by gavage with a single bolus (7.5 mg/kg body mass), only one showed detectable trace levels of FB2 in plasma (25-40 ng/ml over the 3-5 hr period after dosing). This indicates that, like FB1, FB2 has a limited bioavailability. Urinary excretion of FB2 was extremely low, even after i.v. dosing. In total, a mean of 4.1% of the i.v. dose and 0.2% of the gavage dose was recovered in urine over a 7-day period. The predominant route of excretion was via the faeces, mainly as the unmetabolized toxin or as a partially hydrolysed analogue, with the latter accounting for between 6% and 47% of the dose. Limited amounts (maximum of 1.1%) of the fully hydrolysed aminopolyol backbone of FB2 were recovered in faeces.

In vivo effects of fumonisin B1-producing and fumonisin B1-nonproducing Fusarium moniliforme isolates are similar: fumonisins B2 and B3 cause hepato- and nephrotoxicity in rats

Fumonisins are mycotoxins produced by Fusarium moniliforme, F. proliferatum, and related Fusarium species found on corn. They occur naturally in corn-based feeds and foods and are suspected human esophageal carcinogens. Fumonisin B1 (FB1), the most common homologue, causes the animal diseases associated with F. moniliforme. Hepato- and nephrotoxicities, disrupted sphingolipid metabolism, and liver cancer have been found in rats fed FB1. To determine the in vivo effects of diets containing fumonisins B2 (FB2) or B3 or (FB3), male rats were fed culture materials (CM) of FB1 non-producing F. moniliforme isolates to provide low (4.6-6.7 ppm), mid (32-49 ppm) or high (219-295 ppm) dietary levels of either FB2 (FB2CM) or FB3 (FB3CM). Other groups were fed culture material of an FB1 producing isolate (FB1CM) providing 6.9, 53 or 303 ppm total fumonisins (FB1: FB2: FB3 = 1.0: 0.38: 0.15) and a tenth group was fed a control diet having no detectable fumonisins. One-half (n = 5/group) the animals were killed after three weeks, at which time the toxicological and histopathological effects of the three culture materials were similar, mimicked the effects of FB1, and included decreased body weight gains, serum chemical indicators of hepatotoxicity, decreased kidney weights, and apoptosis of hepatocytes and kidney tubular epithelium. FB1CM, FB2CM, and FB3CM affected sphingolipids, causing increased sphinganine to sphingosine ratios (Sa/So) in both liver and kidneys. The remaining animals (n = 5/group0 were fed a control diet for three additional weeks. All body weight and tissue specific effects, including increased Sa/So, induced by the FB2Cm, FB3CM and low level FB1CM diets were absent following the recovery period. Except for mild biliary lesions found in the high dose of FB1CM group and a few apoptotic hepatocytes present in one mid- and two high-dose FB1CM rats, no evidence of toxicity remained in these groups, following the recovery period.

Sensitive method for the detection of fumonisin B1 in human urine

Fumonisins are a group of carcinogenic mycotoxins that occur worldwide. This paper reports a sensitive method for the detection and quantitation of fumonisin B1 in human urine. Amberlite XAD-2 non-ionic polymeric adsorbent resin is used prior to strong anion-exchange (SAX) cartridge clean-up. As much as 100 ml of undiluted human urine can be loaded onto the column. Recoveries obtained using this method were 93.6, 95.1 and 94.4% when samples were spiked with 10, 50 and 500 ng/ml of fumonisin B1, respectively. This method is highly reproducible (R.S.D.<5%) and gives good sample clean-up, which is suitable for HPLC analysis.

Assessment of the embryotoxic potential of the total hydrolysis product of fumonisin B1 using cultured organogenesis-staged rat embryos

Aminopentol (AP1) is the total hydrolysis product of fumonisin B1 (FB1), the major and best characterized of the fumonisins, which are mycotoxins that are common contaminants of corn and corn meal. Some human populations expected to have significant exposure to AP1 have a high incidence of babies born with neural tube defects (NTD). The embryotoxicity of AP1 was evaluated in cultured rat embryos. Gestation day 9.5 embryos were exposed to 0, 3, 10, 30, 100 or 300 microM AP1 throughout the entire 45-hr culture period. At 100 microM AP1, growth and overall development were reduced significantly. There was also a significant increase in the incidence of abnormal embryos. 29% of the embryos had NTD, and 36% of the embryos had other abnormalities. At 300 microM AP1, the incidence of NTD was 15%, and 85% of the embryos had other abnormalities. These findings suggest that AP1, at concentrations of 100 microM and above, can induce NTD in organogenesis-stage cultured rat embryos. However, these NTD are in conjunction with significant overall retardation of growth and development as well as significant increases in the incidence of other defects. These studies also showed, when compared with previous findings, that AP1 is over 100-fold less toxic than FB1 to cultured rat embryos.

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

The presence of fumonisins and associated mycotoxins from Fusarium moniliforme in corn-based foods has recently become a concern in North America and elsewhere. Monitoring of various corn based foods and food commodities for fumonisins is ongoing in both the USA and Canada, and the results can be used for preliminary exposure assessments. The role of Fusarium moniliforme and the fumonisins in some diseases of livestock has been established. Considerable information is available on the mechanism of action of the fumonisins. With the availability of increased quantities of pure fumonisins, several subchronic toxicity studies, designed to establish dose response characteristics in rodents have now been completed. However, since concerns about the chronic toxicity of the fumonisins have not yet been adequately addressed, a tolerable daily intake cannot be established at this time. With the information at hand it is, nevertheless, possible to arrive at an interim risk assessment, which can be used to make interim risk management decisions. A total of 361 samples, covering 4 years of a Canadian survey, have been analyzed to date. Of these, 64 contained > or = 0.1 micrograms/g fumonisin B1, and 10 contained > or = 1 microgram/g. The 'all persons' estimate for the intake of fumonisins from these foods was < 0.089 micrograms/kg bw for 5-11 year-old children, and lower for other age groups. Based on an assessment of the available information on the toxicity of fumonisins, it can be concluded that these estimated intakes are unlikely to pose a health risk.

Fumonisins, mycotoxins of increasing importance: their nature and their effects

The fumonisins (FBs) are a group of closely related mycotoxins that are prevalent in maize. They were isolated from strains of Fusarium moniliforme (Sheldon), which were implicated in the aetiology of human oesophageal cancer in the Transkei, South Africa. Their discovery explained the cause of equine encephalomalacia, or "hole in the head" syndrome, when it was found by feeding trials in horses that they elicited the disease. Subsequently, they were found to cause hepatic cancer in rats and pulmonary oedema in pigs, with most animal species tested showing liver and kidney damage. FB1 is the most important of the group and, although poorly absorbed from the gastrointestinal tract, its action is at the cellular level, affecting sphingolipid metabolism. Ceramides derived from sphingosine metabolism are cell regulatory factors affecting, among other things, DNA synthesis. Because FB1 has a close molecular resemblance to sphinganine, it interferes with ceramide biosynthesis and, hence, the processes that it regulates, which is thought to explain its carcinogenic properties. Studies on the FBs are still at a relatively early stage, but it is already clear that they play an important role in animal mycotoxicoses and, by implication, in human disease. A more positive aspect is that they will be used in elucidating the role of sphingolipids in cellular regulation.

The reliability and significance of analytical data on the natural occurrence of fumonisins in food

Several methods are presently used to identify and quantify fumonisins in foods and feeds. HPLC procedures on derivatized fumonisins with fluorescence detection are most commonly used. The validity and significance of reported fumonisin levels depend on several factors such as the specificity, detection limit, accuracy and reproducibility of the analytical method as well as on the sampling procedure used, and the integrity and purity of the analytical standards. The importance of these factors is discussed and the results of two international collaborative studies are presented on the determination of fumonisins in corn by a reversed-phase HPLC method on o-phthaldialdehyde (OPA) derivatized fumonisins using fluorescence detection.

Mycotoxins, general view, chemistry and structure

Mycotoxins induce diverse and powerful biological effects in test systems; some are carcinogenic, mutagenic, teratogenic, estrogenic, hemorrhagic, immunotoxic, nephrotoxic, hepatotoxic, dermotoxic, and neurotoxic. Mycotoxins have been unambiguously linked to the etiology of several diseases in animals. The discovery of aflatoxins in the early 1960s led to the resurgence of interest in human mycotoxicoses; mycotoxins are now recognized as causal factors of primary liver cancer, ergotism and alimentary toxic aleukia. The fumonisins and ochratoxins are suspected of playing a role in the etiology of esophageal cancer and Balkan endemic nephrotoxicity, respectively.

Toxicokinetics of the mycotoxin fumonisin B2 in rats

Fumonisin B2 (FB2), a secondary metabolite of the fungus Fusarium moniliforme, was administered at a dose of 7.5 mg/kg body weight to male BD IX rats by ip injection or by gavage. FB2 was rapidly absorbed from the peritoneum, its level in plasma reaching a maximum within 20 min after injection. It was rapidly eliminated from plasma with a half-life of 26 min. After 24 hr, FB2 could not be detected in plasma (< 20 ng/ml). Analysis of rat plasma for FB2 following a gavage dose failed to detect any toxin over a 6-hr period after dosing. The elimination of FB2 in the urine and faeces was determined over a 3-day period after dosing. After i.p. injection, the mean urinary excretion over this period was 1.2% and faecal elimination accounted for 84.1% of the dose. Similarly, after dosing by gavage, 0.2 and 82.0% of the dose was recovered in urine and faeces, respectively. FB2 appeared to be excreted unmetabolized.

Fate of a single dose of 14C-labelled fumonisin B1 in vervet monkeys

The mycotoxin fumonisin B1 (FB1) was dosed as 14C-labelled FB1, to male vervet monkeys (Cercopithecus aethiops) both by intravenous (i.v.) injection (2 monkeys, dose 1.72 mg [86 kBq]/kg body weight) and by gavage (2 monkeys, dose 6.42 mg [321 kBq]/kg body weight). Excreta were collected over a 24-hr period, whereafter the monkeys were sacrificed and selected organs and contents of the gut collected to determine the distribution of the 14C-label. The bulk of the radioactivity recovered from tissue was found in the liver (mean of 1.92% in i.v.-dosed monkeys; 0.64% in gavage-dosed monkeys). Of the other organs analysed, the following mean amounts of radioactivity were recovered in organs of i.v.- and gavage-dosed monkeys, respectively: muscle, 0.62% and 0.14%; kidney, 0.37% and 0.03%; brain, 0.08% and 0.02%; lung, 0.07% and 0.03%; heart, 0.04% and 0.01%; spleen, 0.02% and < 0.01%; plasma, 0.66% and 0.12%; red blood cells, 0.11% and 0.01%; while a further 68.1% and 64.0% were recovered in excreta, bile, and the gut contents. Analysis of faeces and gut contents showed that radioactivity was due to FB1, its partially hydrolysed metabolites, and trace amounts of the fully hydrolysed aminopentol moiety. Analysis of bile showed an absence of hydrolysis products, indicating that hydrolysis occurred only in the gut, resulting in the removal of the tricarballylic acid moiety at the C14-position. Determination of FB1, levels in plasma following a gavage dose indicated that only limited amounts of FB1 were absorbed, as plasma levels peaked after 1-2 hr with levels below 210 ng/ml.