Assessing chronic exposure to fumonisin mycotoxins: the use of hair as a suitable noninvasive matrix

This study describes for the first time the accumulation of measurable levels of fumonisin mycotoxins in the hair of nonhuman primates (vervet monkeys, Cercopithecus aethiops) and rats exposed to contaminated feed. Hair was subjected to reflux with methanol, and the resulting extract was cleaned up on strong anion exchange (SAX) and C18 solid-phase sorbents. Fumonisins FB1, FB2, and FB3 as well as their hydrolysis products commonly known as aminopolyols, AP1 and AP2, were detected in monkey hair using high-performance liquid chromatography coupled to electrospray ionization mass spectrometry (HPLC-ESI-MS). Despite matrix interferences, the two-stage mass spectrometric process (MS-MS) yielded product ion mass spectra, which served as diagnostic indicators thus providing unequivocal identification of FB1, FB2, and FB3 as well as AP1 and AP2. In vervet monkeys, the levels of exposure related well to the levels of toxin detected in hair, and levels as high as 5.98 mg FB1, 33.77 mg FB1, and 65.93 mg FB1/kg of hair were found in monkeys receiving control, low-dose, and high-dose contaminated diets, respectively. Hair was also analyzed from rats given either single gavage doses of 1 and 10 mg FB1/kg body weight or contaminated feed (50 mg FB1/kg), resulting in an exposure of approximately 4.25 mg FB1/kg body weight/day based on the measured daily feed intake. Analysis of rat hair over a four-week period indicated that mean levels up to 34.50 mg/kg and 42.20 mg/kg were detectable by the fourth week in the rats treated by gavage (10 mg FB1/kg body weight) and those receiving contaminated feed, respectively. This relationship indicates that hair can provide an easily applicable non-invasive matrix for assessing chronic exposure to fumonisin mycotoxins.

Toxicokinetics of ochratoxin A in vervet monkeys (Cercopithecus aethiops)

The toxicokinetics of ochratoxin A were investigated in vervet monkeys (Cercopithecus aethiops). Three female monkeys were treated intravenously with ochratoxin A at doses, respectively, of 0.8, 1.5 and 2 mg/ kg body weight (BW). Blood and urine samples were collected over a period of 21 days. Plasma and urine extracts were analysed by high-performance liquid chromatography (HPLC) with either fluorescence or negative ion electrospray ionization mass spectrometric detection. The clearance of ochratoxin A from plasma followed a two-compartment model. The elimination half-life of ochratoxin A in the monkeys was determined to be 19-21 days and the average total body clearance was 0.22 +/- 0.07 ml/h per kg and the average apparent distribution volume of the central compartment was 59 +/- 9 ml/kg and the peripheral compartment was 59 +/- 20 ml/kg. No evidence was found for any metabolic conversion of ochratoxin A.

Determination of patulin in apple juice by high-performance liquid chromatography-atmospheric pressure chemical ionization mass spectrometry

An HPLC-MS-MS method with selected reaction monitoring (SRM) for the determination of patulin in apple juice samples is described. Mass spectrometric detection was accomplished following atmospheric pressure chemical ionization (APCI) in both positive and negative ion modes. Collision induced dissociation (CID) of the protonated molecular ion led initially to the loss of H2O (fragment m/z 137). At higher energies CO is lost from both the protonated parent molecule (fragment m/z 127) and the dehydrated molecular ion (fragment m/z 109). In contrast, CID of the deprotonated molecular ion led initially to the fragment at m/z 109 corresponding to the loss of either CO2 or acetaldehyde, followed at higher CID energy by the loss of H2O (fragment m/z 135) and CO (fragment m/z 125) from the deprotonated molecular ion. Detection in the negative ion mode proved superior and a linear response was observed over the injected range from 6 to 200 ng patulin. Apple juice samples spiked with patulin between 10 and 135 microg/l were analyzed following liquid-liquid extraction with ethyl acetate and clean up with sodium carbonate. Utilizing reversed-phase HPLC with acetonitrile-water (10:90) at 0.5 ml/min, levels down to 10 microg/l were readily quantified and a detection limit of 4 microg/l was attainable at a signal-to-noise (SIN) ratio of 4. The MS data for the spiked samples compared well to the UV data and when plotted against each other displayed a correlation coefficient (R) of 0.99.

Production of the mycotoxins fusaproliferin and beauvericin by South African isolates in the Fusarium section Liseola

The production of fusaproliferin (FUS), a recently described mycotoxin, and beauvericin (BEA), a mycotoxin recently reported to co-occur with FUS in Fusarium-infected corn, by South African isolates in the Fusarium section Liseola, was investigated. Five isolates each of F. verticillioides, F. proliferatum, F. subglutinans, and F. globosum were cultured on corn kernels. Four each of the five South African isolates of F. proliferatum and F. subglutinans produced FUS (10-1725 and 330-2630 mg/kg, respectively). BEA was produced by four of the F. proliferatum strains (310-1130 mg/kg) and three of the F. subglutinans strains (140-700 mg/kg). The isolates of F. verticillioides failed to produce significant levels of either of these secondary metabolites. F. globosum was a weak producer of both in that one isolate of five produced 25 mg/kg FUS and five out of five produced BEA at levels ranging between 10 and 110 mg/kg. To further characterize these strains, their production of fumonisins B(1), B(2), and B(3), as well as moniliformin, was investigated. Of the four species investigated, fumonisins were produced by all except F. subglutinans, which in turn was the only species whose isolates in this study produced moniliformin (four of five isolates, ranging from 155 to 2095 mg/kg). Analysis of visibly Fusarium-infected home-grown corn collected in the Transkei region of the Eastern Cape Province of South Africa showed that nine of the ten samples contained low levels of FUS (up to 62 microg/kg), whereas all ten samples showed BEA contamination ranging from 8 to 1734 microg/kg with a mean of 258 microg/kg.

Determination of the Fusarium mycotoxins, fusaproliferin and beauvericin by high-performance liquid chromatography-electrospray ionization mass spectrometry

A method is described using LC-MS for the detection of the mycotoxins fusaproliferin (FUS) and beauvericin (BEA) in cultures of Fusarium subglutinans and in naturally contaminated maize. Protonated molecular ion signals for FUS and BEA were observed at m/z 445 and m/z 784, respectively. Collision induced dissociation of the readily dehydrated protonated molecular ion of the sesterterpene FUS (m/z 427) led to the loss of another water molecule (m/z 409) and acetic acid (m/z 385), while the cyclic lactone trimer BEA fragmented to yield the protonated dimer (m/z 523) and monomer (m/z 262), respectively. Detection of FUS was best performed in the MS-MS mode while BEA displayed a stronger signal in the MS mode. The on-column instrumental detection limits for pure FUS and BEA were found to be 2 ng and 20 pg (S/N=2) while those in naturally contaminated maize were 1 microg/kg and 0.5 microg/kg, respectively. Five South African strains of F. subglutinans were analyzed following methanol extraction of which four produced FUS at levels between 330 mg/kg and 2630 mg/kg while only three produced BEA at levels between 140 mg/kg and 700 mg/kg. Application of this method to naturally contaminated maize samples from the Transkei region of South Africa showed FUS at levels of 8.8-39.6 microg/kg and BEA at 7.6-238.8 microg/kg.

Determination of the mycotoxin moniliformin in cultures of Fusarium subglutinans and in naturally contaminated maize by high-performance liquid chromatography-atmospheric pressure chemical ionization mass spectrometry

A LC-MS method employing triethylamine as ion-pairing reagent for the determination of moniliformin in culture material and naturally contaminated maize samples is described. Mass spectrometric detection of moniliformin was accomplished following atmospheric pressure chemical ionization to yield the deprotonated molecular ion [M-H]- at m/z 97. The moniliformin response was found to be linear over the injected range 10 ng to 700 ng and a detection limit of 10 ng was attainable at a signal-to-noise (S/N) ratio of 4. Five South African strains of Fusarium subglutinans were grown on maize kernels and moniliformin extracted with an acetonitrile-water (95:5) mixture. Following sample clean up with reversed-phase (C18) solid-phase extraction cartridges, the extracts were subjected to LC-MS analysis. Triethylamine was used as an ion-pair reagent and found to improve the retention characteristics of moniliformin without any detrimental effects to the instrument. Moniliformin concentrations ranged between 130 mg/kg and 1460 mg/kg culture. Application of this method to naturally contaminated maize samples from Transkei showed that it was capable of measuring moniliformin levels down to 10 micrograms/kg in selected moldy maize cobs. This is the first report on the application of LC-MS to the analysis of moniliformin in cultures of F. subglutinans and in naturally contaminated maize.