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The level of aflatoxin varies in the hulls, seed coats, and kernels of pistachios. Inoculation of fresh pistachio kernels with Aspergillus flavus produced colonies of A. flavus in wounded kernels, with the seed coat or without it. The fungal colonies and aflatoxin were undetected in intact kernels without seed coats. Fungal colonies could be found in the hulls but not aflatoxin. Wounded kernels with hulls had lower levels of aflatoxin than kernels without hulls.

A biosynthesis of aflatoxin B1 involved the incorporation of (super 18)O molecular oxygen at C-16, C-8, and C-1. Efficient (super 18)O-labeling were observed at the three carbon positions. The incorporation of (super 18)O at C-1 involved a two-step mechanism of the final oxidative steps in the biosynthesis. Xanthone underwent a monooxygenase reaction followed by the cleavage of the A-ring. This resulted to another monooxygenase reaction forming the reactive intermediate which eventually rearranged and decarboxylated to aflatoxin B1.

Aflatoxins are produced by the fungi Aspergillus flavus and A. parasiticus and are toxic and carcinogenic secondary metabolites. The GAP13 construct is a suitable genetic tool to study the induction of aflatoxin in situ and to measure the activation of gene for aflatoxin biosynthesis. Aflatoxin accumulation, transcript analysis and beta-glucuronidase(GUS) expression shows that the GAP13 reporter construct effectively regulates the activity of ver1 gene independent of culture conditions. The reporter construct was obtained by fusing the promoter region of ver1 with the GUS and also from the maize kernels.

Aflatoxins are biologically active secondary metabolites made by Aspergillus parasiticus, A. nomius and A. flavus fungi and can be deadly to humans if they are ingested. Genes involved in aflatoxin biosynthesis can be cloned to help generate understanding of the molecular biology that creates the toxins, as the cloned genes extract the molecular mechanisms that controls the expression and the timing of these genes. Analysis of the biosynthesis can provide insight on how to prevent the toxins from forming in foods.

Nucleotide sequence and transcript mapping analyses help analyze the physical structure of the nor-1 gene that regulates the biosynthesis of aflatoxins by Aspergillus parasiticus. Primer extension and RNase protection analyses and a comparison of the nucleotide sequence of the nor-1 genomic and cDNA clones yield the transcription initiation and polyadenylation sites. Aflatoxin production levels decrease when Aspergillus parasiticus NR-3 (niaD Afl+) is transformed with the plasmid, pNA51-82, yielding niaD+ transformants that accumulate norsolorinic acid.

3', 5'-bis(O-tert-butyldimethylsilyl) derivative of 2'-deoxy adenosine reacts with an epoxide producing an adenine N7 adduct. NMR experiments reveal the occurrence of adduction at N7 positive of the base through trans opening of the epoxide. Use of this sample reveals the formation of adenine N7 adduct in the reaction of aflatoxin B1 exo-8,9-epoxide with calf thymus DNA. NMR studies using various substituted methyladenines suggest guidelines for predicting assignments on the aflatoxin adduct.

Experimental studies on the influence of neem leaf volatiles on submerged cultures of aflatoxigenic Aspergillus parasiticus show that volatile components of neem leaves affect fungal growth and aflatoxin production in A. parasiticus. Gas spectroscopy-mass spectroscopic study of the neem volatiles reveals the presence of 68 compounds and 10% of the total headspace volatiles constitute C3 to C9 alkenals, which are toxic to aflatoxigenic. A. spp, explaining the reduced biomass in neem-treated cultures due to bioactivity.

Two Aspergillus homologous genes, afl2 and apa2, regulate aflatoxin biosynthesis and are termed aflR genes. The aflR codes for a protein that contains a zinc cluster DNA-binding motif are present in various fungal transcriptional regulatory proteins. Genes with DNA sequences similar to aflR are expressed in the species. The A. oryzae and A. sojae aflR locus encodes an antisense transcript whose accretion destabilizes mRNA.

Five atoxigenic Aspergillus flavus strains repress aflatoxin contamination by toxigenic strains in cottonseeds and transform aflatoxin precursors to aflatoxin B1 to reduce contamination. The AF36 strain was the most effective in inhibiting contamination when simultaneously inoculated with toxigenic strains. The conversion of aflatoxin precursors to aflatoxin B1 reveals an aflatoxin biosynthetic pathway in the strains.

The aflatoxin B1 (AFBI) exo epoxide isomer reacts with DNA through an S2 mechanism, resulting in specific trans ring opening of the isomer, whereas the endo isomer is inactive. Dymethyldioxirane-catalyzed oxidation or cytochrome p450 oxidase-catalysed enzymatic reactions yield the two AFB1 isomers. The results confirm that the exo epoxide is the potent mutagen in AFB1.

Studies on whether homologous recombination of changing DNA and genomic DNA can be employed to stop the working of a model gene cloned from Aspergillus parasiticus were undertaken. The niaD gene was employed due to simple positive and negative selection procedure formulated to examine nitrate reductase function. The technique employed in the blocking of niaD gene can be used to induce non-aflatoxin-producing strains for use as biocontrol catalysts.

The volatile compounds produced by atoxigenic and toxigenic strains of Aspergillus flavus were analyzed by gas chromatography-mass spectrometry. The results showed a correlation between aflatoxin biosynthesis and the production of sesquiterpenes. Moreover, a decline in aflatoxin concentration also resulted in the decline of emitted volatile sesquiterpenes. These results have implications in the molecular regulation of aflatoxin biosynthesis.

Three trials using 207 crossbred pigs were conducted to evaluate the effects of aflatoxin-contaminated corn on young pigs and to determine whether several nutritional and nonnutritional dietary amendments would benefit performance or health in situations of aflatoxin |B.sub.1~ contamination. In Trial 1 using 90 pigs in a 49-d trial, linear (P |is less than~ .01) and quadratic (P |is less than~ .05) decreases in ADG were observed with increasing (0, 420, 840 ppb) dietary aflatoxin level. This growth decrease was associated with linear reductions (P |is less than~ .01) in ADFI and decreases in gain/feed. Serum indicators of protein synthetic capabilities and of liver damage were also adversely affected. Improvements in growth rate for the total trial period in the presence of 840 ppb of aflatoxin were obtained with the addition of the 2 ppm of folic acid (P |is less than~ .05) or .5% hydrated sodium calcium aluminosilicate (HSCA) (P |is less than~ .01); the magnitude of improvement was greater for the HSCA. The addition of HSCA to the contaminated diet also restored the serum clinical chemistry profile to that exhibited by pigs fed the diet without contaminated corn. The addition of .6 ppm of Se to a basal diet containing .3 ppm of Se was generally without effect. In Trial 2, 63 pigs were used in a 42-d trial to further assess the effectiveness of both folic acid and HSCA, as well as of two sodium bentonites, in reducing the effects of aflatoxin from naturally contaminated diets (800 ppb of aflatoxin). Folic acid had no positive effect in this trial, but HSCA improved ADG (P |is less than~ .01) and all clinical chemistry indicators that had been negatively affected by the contaminated diet (P |is less than~ .05). Both sodium bentonites provided as much improvement in ADG (P |is less than~ .01) as the HSCA and also improved all clinical chemistry indicators that had been adversely affected by the aflatoxin (P |is less than~ .05). In Trial 3 using 54 pigs in a 42-d trial, linear (P |is less than~ .05) and quadratic (P |is less than~ .025) improvements in ADG and ADFI and linear (P |is less than~ .05) improvements in those serum clinical chemistry indicators adversely affected by the contaminated diet were observed with additions of .25, .50, and .75% sodium bentonite to a diet naturally contaminated with 800 ppb of aflatoxin. There was no benefit to including more than .50% sodium bentonite to the contaminated diet. In situations of aflatoxin contamination, dietary alterations or additions can be made to diminish the adverse effects of aflatoxin.

Aspergillus flavus and A. parasiticus are naturally occurring soil fungi that are capable of invading food and feed crops and contaminating them with aflatoxin. Aflatoxin is a human carcinogen produced [...]

The effects of mycotoxins on the reproduction of domestic livestock are evaluated. Mold contamination of animal feed is already being studied, but many mycotoxins remain unaffected by mold inhibitors. Aflatoxin, ochratoxin, ergot, doexynivalenol and zearalenone are the five most significant mycotoxins in North America. Of these, zearalenone is the most important, as it possesses estrogenic activity. Although mycotoxins can be detected by laboratory studies, field techniques which will allow detection on farms and grain elevators would allow more effective monitoring.

Spectroscopic studies reveal evidence of enal and epoxide formation as intermediates in the metabolism of furans, of interest biomedically as aflatoxins. Menthofuran, a potentially toxic terpene in mint oil, was oxidized with dimethyldioxirane to ultimately form stable ene lactones. H NMR monitors detected chemical shift values akin to the hemiacetal proton of the 8,9-epoxide of aflatoxin B1, interpreted as hemiacetal protons in diastereomeric epoxides formed from methofuran. This was corroborated by C NMR and FAB MS data on related reactions.

West African Aspergillus section Flavi isolates differ from those found in North America. While both isolates produce aflatoxin B, 40 and 100% of West African isolates also produce aflatoxin G(sub 1) in NH(sub 4) medium and urea medium, respectively. In contrast, North American isolates do not produce aflatoxin G(sub 1). This physiological and geographical divergence of West African and North American isolates of Aspergillus section Flavi may affect aflatoxin management.

The gene disruption and enzyme activity of hypC, an open reading frame in the region between the pksA (aflC) and nor-I (aflD) genes in the aflatoxin biosynthesis gene cluster is reported. The gene HypC, the anthrone oxidase involved in aflatoxin biosynthesis encodes a 17-kDa oxidase that converts norsolorinic acid anthrone to nonsolorinic acid.

A study conducted reported on extrusion-cooking as an effective means of removing total Aflatoxins (AF) from contaminated rice meal. Extrusion-cooking was observed to reduce aflatoxin (AF) content, which ranged from 51% to 95% depending on the type of AF and the studied variables.

Three enzymes encoded by verA, Ver-1 and aflY are required for conversion of versicolorin A (VA) to demethylsterigmatocystin and a study was conducted to show that a fourth enzyme encoded by a previously uncharacterized gene, aflX (ordB) is also required for this conversion. The protein encoded by aflX is predicted to have domains typical of an NADH-dependent oxidoreductase and has 27% amino acid identity to a protein encoded by the aflatoxin cluster gene, aflO (avfA).

A novel method of toxin inactivation using aqueous ajowan extract is described and the inactivation factor (IF), which is responsible for the activity, is studied. Thin layer chromatography analysis of the toxins after treatment with IF showed relative reduction of aflatoxin G(sub 1)>G(sub 2)>B(sub 1)>B(sub 2).

Studies done to determine whether AFB1 and intestinal mucus influence each otherEs binding by surface structures of two probiotic preparations are reported. The results reveal that probiotics adhering to the intestinal wall are less likely to bind and consequently accumulate AFB1 in the host and on the other hand probiotics with AFB1 bound to their surfaces are less likely to adhere to the intestinal wall and prolong expose to dietary AFB1. It is concluded that specific probiotics may be potent and safe means to reduce absorption and increase excretion of dietary AFB1 from the body.

Research has demonstrated that 25 identified genes clustered within a 70-kb DNA region in the chromosome are involved in aflatoxin biosynthesis. These genes and their enzymes involved in aflatoxin biosynthetic pathway are reviewed and a new naming scheme that follows the naming convention in Aspergillus is proposed.

Research indicates that the mismatched C(sup)5-A9sup)16 base pair positioned 5' to an (sup)AFBG damage sites exhibits predominantly wobble conformation existing as a mixture of protonated and nonprotonated species. Furthermore, an adducted DNA duplex accommodates the wobble pair with minor perturbation.

Natural natrolite zeolite is used to neutralize pistachio nuts obtained by floating-nut separation. It was found that such separation generally yields nuts that are smaller and lighter with distinctive dark brown discoloration along the shell structure as well as insect-infected kernels and those containing highly variable levels of aflatoxins.

For this work, two different plastic microfluidic devices are designed and fabricated for applications in high-throughput residue analysis of food contaminants and drug screening of small-molecule libraries. Microfluidic networks on copolyester and poly(dimethylsiloxane) substrates are fabricated by silicon template imprinting and capillary molding techniques. The first device is developed to perform affinity capture, concentration, and direct identification of targeted compounds using electrospray ionization mass spectrometry. Poly(vinylidene fluoride) membranes sandwiched between the imprinted copolyester microchannels in an integrated platform provide continuous affinity dialysis and concentration of a reaction mixture containing aflatoxin [B.sub.1] antibody and aflatoxins. The second microfluidic device is composed of microchannels on the poly(dimethylsiloxane) substrates. The device is designed to perform miniaturized ultrafiltration of affinity complexes of phenobarbital antibody and barbiturates, including the sequential loading, washing, and dissociation steps. These microfabricated devices not only significantly reduce dead volume and sample consumption but also increase the detection sensitivity by at least 1-2 orders of magnitude over those reported previously. Improvements in detection sensitivity are attributed to analyte preconcentration during the affinity purification step, limited analyte dilution in the microdialysis junction, minimal sample loss, and the amenability of ESI-MS to nanoscale sample flow rates.

Many disease-causing filamentous fungi of plants and animals produce toxins, notorious among these is aflatoxin, which can cause liver cancer in people and livestock who have eaten affected nuts and [...]