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PubMed1986

Effect of metal ions on aflatoxin production by Aspergillus parasiticus.

The effect of iron, copper, cobalt, cadmium, zinc, molybdenum, magnesium and manganese salts was studied on aflatoxin production in relation to mycelial mass. Iron, copper and cadmium salts decreased the aflatoxin production to different levels but a mixed trend was observed depending on salt concentration, with molybdenum, magnesium and manganese. Cobalt and zinc salts stimulated aflatoxin production at all concentrations studied. The maximum increase in aflatoxin production, 655% and 519% was observed in the presence of zinc sulfate and sodium molybdate, respectively. A negative correlation was observed between aflatoxin production and vegetative growth of fungus.

Aflatoxins↗

PubMed2002

Variability in nitrogen regulation of aflatoxin production by Aspergillus flavus strains.

Aflatoxins are toxic and carcinogenic metabolites of several Aspergillus species. The effect of nitrate on aflatoxin production and expression of the key regulatory genes involved in aflatoxin biosynthesis, aflR and aflJ, were compared among isolates of the S(B) and S(BG) strains of A. flavus. Aflatoxin production by two of the three strain S(B) isolates did not differ significantly between the two media tested, whereas for S(BG) A. flavus isolates, the level of aflatoxins in buffered nitrate medium was as much as 20-fold lower than in ammonium salts medium. Expression of aflR was not significantly affected by growth of cultures in nitrate medium for most of the isolates. However, on nitrate medium, expression of aflJ was 2.6-fold higher for the S(B) isolates than it was on ammonium salts medium, whereas for the S(BG) isolates aflJ expression was 2-fold lower on nitrate than on ammonium salts medium. This difference may result from the presence in the aflJ/aflR intergenic region of S(BG) isolates of fewer putative binding sites (HGATAR sites) for AreA, the positive-acting, wide domain transcription factor involved in regulation of nitrogen metabolism.

Aflatoxins↗

PubMed2001

Pre-termination in aflR of Aspergillus sojae inhibits aflatoxin biosynthesis.

The aflR gene product is the main transcriptional regulator of aflatoxin biosynthesis in Aspergillus parasiticus and Aspergillus flavus. Although A. sojae strains do not produce aflatoxins, they do have an aflR homologue. When compared with the aflR of A. parasiticus, the A. sojae gene contains two mutations: an HAHA motif and a premature stop codon. To investigate the functionality of the A. sojae aflR gene product, we used a GAL4 one-hybrid system in yeast. The transcription-activating activity of AflR from A. sojae was 15% of that from A. parasiticus. The introduction of an additional aflR from A. sojae into an A. parasiticus strain did not affect aflatoxin productivity. A hybrid aflR comprising the amino-terminal region of A. sojae aflR and the carboxy-terminal region of A. parasiticus aflR suppressed the effect associated with pre-termination of the A. sojae AflR. We conclude that the premature stop codon of the A. sojae aflR is the key to its functionality and leads to prevention of aflatoxin biosynthesis through loss of the transcription of aflatoxin biosynthesis-related genes.

Aflatoxins↗

PubMed2005

Validation of an ELISA test kit for the detection of total aflatoxins in grain and grain products by comparison with HPLC.

An ELISA Microtiter Plate, Total Aflatoxin Test called AgraQuant was validated to measure total aflatoxins in a range from 4 to 40 ppb in corn, corn meal, corn gluten feed, corn gluten meal, corn germ meal, corn/soy blend, popcorn, sorghum, wheat, milled rice, soybeans, peanuts and cottonseed. The test is performed as a solid phase direct competitive ELISA using a horseradish peroxidase conjugate as the competing, measurable entity. For the test method, aflatoxins are extracted from ground samples with 70% methanol and sample extracts plus conjugate are mixed and then added to the antibody-coated microwells. After 15 min incubation at room temperature, the plate is washed and enzyme substrate is added and allowed to incubate for an additional 5 min. Stop solution is then added and the intensity of the resulting yellow color is measured optically with a microplate reader at 450 nm. Results obtained from internal validation studies assessing accelerated stability indicate a minimum of 1 year shelf life for the kits; accuracy and precision are comparable to HPLC in the range of 0-320 ppb and limit of detection in corn is 2.5 ppb. Comparison of the method to HPLC, ability to detect individual aflatoxins and ruggedness of the test kits at 18-30 degrees C determined this test to be rugged, sensitive, accurate, precise and effective comparable to HPLC for measuring total aflatoxins ranging from 4 to 40 ppb in the commodities evaluated.

Aflatoxins↗

PubMed2006

Does aflatoxin as an environmental mycotoxin adversely affect the renal and hepatic functions of Egyptian lactating mothers and their infants? A preliminary report.

BACKGROUNDS/AIMS: Aflatoxin as a mycotoxin constitutes a real human threat. Its presence in human milk was previously reported in different countries. This work is the first Egyptian report that aimed to assess the presence of aflatoxin in both mothers' milk and the infants' sera and studied its correlation with infants' kidney functions. METHODS: Fifty healthy breast lactating mothers and their infants who were exclusively breast fed for at least 4 months were included. All of them were subjected to thorough laboratory evaluation including determination of aflatoxin concentration by high performance liquid chromatography. RESULTS: Twenty-four mothers (48%) and their infants had been contaminated with aflatoxin with the following mean contamination levels (ng/ml); mothers' serum of 8.9+/-4.2, mothers' milk of 1.9+/-0.6 and infants' serum of 1.8+/-0.9. The presence of this contamination level is not associated with renal or hepatic dysfunction. CONCLUSION: Mothers and their infants in our locality showed a relatively high aflatoxin contamination rate. We did not find a correlation of this contamination level and either renal or hepatic dysfunction.

Adult↗

PubMed2006

Potential aflatoxin and ochratoxin a production by Aspergillus species in poultry feed processing.

Poultry feeds are prone to fungal growth and mycotoxin production during processing. The identification of biota with the ability to produce mycotoxins is essential. The aims of this study were (1) to monitor the mycobiota counts at different stages of poultry feed processing; (2) to determine the occurrence of Aspergillus species; (3) to evaluate the natural incidence of aflatoxins and ochratoxin A. The ability of Aspergillus spp. and its teleomorphs isolated here to produce these toxins was also investigated. Samples (144) were collected at random from a factory in Brazil. The occurrence of Aspergillus and Eurotium species was demonstrated on DRBC and DG18 media and the production of aflatoxins and ochratoxin A and their natural incidence were determined by TLC and HPLC methods. A. flavus and E. chevalieri were the most prevalent species isolated. Fungal contamination was not found after the pelleting process, though Aspergillus and Eurotium species were recovered from trough samples. High levels of aflatoxin and ochratoxin A producers were found at all stages of poultry feed processing. Also, high natural contamination with aflatoxins and ochratoxin A was found in the samples. Contact of feed with remainder poultry feed could lead to fungal contamination, so the risk of aflatoxin and/or ochratoxin A contamination of feed must be taken into account.

Aflatoxins↗

PubMed1978

Fluorescence studies of the interactions of serum albumin and rat alpha1-fetoprotein with aflatoxin B1. Specificity and binding parameters.

The interaction of bovine serum albumin and rat alpha1-fetoprotein with aflatoxin B1 has been followed by the fluorescence quenching of the protein in presence of the ligand. The binding parameters (n, number of sites and Kd, dissociation constant) have been determined for the bovine serum albumin-alflatoxin B1 system: n = 3.5 and Kd = 3.1 +/- 0.5 . 10(-5) M and for the alpha-fetoprotein-aflatoxin system: n = 4 and Kd = 3.7 +/-0.5 . 10(-5) M. The competition of anilino-naphthalene-sulfonate and aflatoxin B1 for the same hydrophobic sites on bovine serum albumin has been demonstrated. The fluorescence quenching of various proteins (lysozymes, egg-albumin, gamma-globulin) by aflatoxin B1 have shown that there is not a strict specificity of aflatoxin towards proteins.

Aflatoxins↗

PubMed1975

Effect of aflatoxins on oxidative phosphorylation by rat liver mitochondria.

The in vitro effect of aflatoxins M1, B1 and G1 on oxidative phosphorylation by rat liver mitochondria with succinate as substrate has been studied. All these toxins inhibit the electron transport chain at a 1-10-4 M concentration and the site of inhibition is between cytochrome b and cytochrome c or c1. Aflatoxin M1 (AFM1) uncouples oxidative phosphorylation at a concentration of 1-10-6 M and reduces the ADP:O ratio, whereas aflatoxin B1 (AFB1) at 1-10-6 M concentration uncouples oxidative phosphorulation but does not affect the ADP:O ratio. At a concentration of 1-10-5 M, AFB1 also decreases the ADP:O ratio along with the uncoupling of oxidative phosphorylation. Aflatoxin G1 (AFG1) acts as an uncoupler at a relatively higher concentration of 1-10-4 M. Preincubation of mitochondria with these aflatoxins resulted in inhibition of respiration and uncoupling of rat liver mitochondria.

Adenosine Diphosphate↗

PubMed1977

Effect of aflatoxin B1 on hepatic polyribosomes and protein synthesis in the rat.

This study was concerned with the effect of aflatoxin B1 on protein synthesis in rat liver. Specifically, the effect of the administration of aflatoxin B1 (6.0 mg/kg body weight) on hepatic polyribosomes (free and membranebound), protein synthesis in vitro, and initiation factors activity of rats within 3-12 h was investigated. The results revealed that aflatoxin B1 rapidly led to disaggregation of free and membrane-bound polyribosomes, to inhibition of in vitro protein synthesis by both populations of polyribosomes, to little or no effect on the activities of initiation factors, and to defective ribosomes, particularly the 60S ribosomal subnits, of both types of polyribosomes. Comparative studies on the effects of aflatoxin B1 and actinomycin D revealed progressive disaggregation by both hepatic free and membrane-bound polyribosomes after aflatoxin B1 but not only of the free polyribosomes after actinomycin D.

Aflatoxins↗

PubMed1977

Comparison of the genetic activity of aflatoxins B1 and G1 in Escherichia coli and Saccharomyces cerevisiae.

The ability of aflatoxins B1 and G1 to induce back mutations to arg+ in Escherichia coli K-12/343/113 was compared with the induction of mitotic gene conversion to ade+ in the diploid yeast strain Saccharomyces cerevisiae D4, ade-2. In analogy to previous results with other microorganisms, the compounds were not genetically active per se, indicating that under the experimental conditions employed none of the tester strains were able to activate the compounds to mutagenic products. In experiments using liver homogenates (S-9 fraction) of male Golden Syrian hamsters previously treated with phenobarbital, aflatoxin B1 exhibited strong genetic activity both in E. coli and in S. cerevisiae, whereas the mutagenic activity of aflatoxin G1 was markedly lower and could be detected only in the E. coli tester strain. These results correlate the findings that aflatoxin G1 is a less potent carcinogen and mutagen than aflatoxin B1.

Aflatoxins↗

PubMed1993

A review of the dose-response induction of DNA adducts by aflatoxin B1 and its implications to quantitative cancer-risk assessment.

The induction of DNA adducts by aflatoxin B1 in the liver has been extensively reviewed in a quantitative cancer-risk assessment of aflatoxins (CDHS, 1990). Rat is the most sensitive species for aflatoxin tumorigenesis and liver is the most sensitive site. In vitro DNA-adduct studies were mostly on adduct identification and specificity of binding. In vivo studies provided dose-response relationship of aflatoxin B1, binding to DNA and DNA-adduct formation. Most in vivo studies were conducted in rats. The dose-response curves of DNA-adduct induction after ingestion or injection treatments in this species were reviewed. A linear dose-response relationship was observed in both injection and ingestion studies at low doses. For cancer-risk assessment, this observation is consistent with the assumption of the linear dose-response risk-assessment model for genotoxic agents, and justifies the use of this model for quantitative cancer-risk assessment for aflatoxins.

Aflatoxin B1↗

PubMed1984

Activities of tryptophan-metabolizing enzymes in liver and brain of rats treated with aflatoxins.

Male Sprague-Dawley rats were treated ip twice daily for 10 days with mixed aflatoxins (10 micrograms/kg body weight) and then the activities of liver tryptophan 2,3-dioxygenase and brainstem tryptophan 5-hydroxylase were determined in vitro. Total tryptophan 2,3-dioxygenase activity was reduced by aflatoxin treatment while holoenzyme activity was not. Induction of tryptophan 2,3-dioxygenase activity by L-tryptophan was not altered by the treatment though induction by hydrocortisone was blocked. It is suggested that aflatoxin may alter the tryptophan 2,3-dioxygenase-haem bond in vivo rather than affect enzyme or cofactor synthesis. Kinetics studies performed in vitro on brain tryptophan 5-hydroxylase showed that aflatoxin treatment in vivo increased the Km of the hydroxylase when L-tryptophan and synthetic 6,7-dimethyl-5,6,7,8-tetrahydrobiopterin were used as the substrate and cofactor, respectively. However, aflatoxin treatment did not alter the Vmax of tryptophan-5-hydroxylase.

Aflatoxins↗

PubMed1992

Reversal of aflatoxin induced liver damage by turmeric and curcumin.

The effect of certain food additives on aflatoxin production by Aspergillus parasiticus has been studied in vitro. Extracts of turmeric (Curcuma longa), garlic (Allium sativum) and asafoetida (Ferula asafoetida) inhibited the aflatoxin production considerably (more than 90%) at concentrations of 5-10 mg/ml. Similar results were also seen using butylated hydroxytoluene, butylated hydroxyanisole and ellagic acid at concentration 0.1 mM. Curcumin, the antioxidant principle from Curcuma longa did not have any effect on aflatoxin production. Turmeric and curcumin were also found to reverse the aflatoxin induced liver damage produced by feeding aflatoxin B1 (AFB1) (5 micrograms/day per 14 days) to ducklings. Fatty changes, necrosis and biliary hyperplasia produced by AFB1 were considerably reversed by these food additives.

Aflatoxins↗

PubMed2004

Natural occurrence of moulds and aflatoxin B1 in melon seeds from markets in Nigeria.

Shelled melon seeds (Colocynthis citrullus L.) were purchased from markets in randomly selected villages and towns in three states in each of the rain forest (Ogun, Oyo and Osun) and Northern guinea savanna (Kaduna, Niger and Bauchi) zones of Nigeria. The seed samples were analysed for incidence of visibly diseased seeds, moisture content, moulds and aflatoxin B1 contamination. The incidence of diseased seeds ranged from 6.4% to 50.4% in the forest, and 4.3% to 34.3% in the savanna, and the moisture content was 5.6% to 12.6% and 4.5% to 10.3%, respectively. Mould evaluation revealed that Aspergillus was the most frequent genus, followed by Penicillium, Botryodiplodia, Cladosporium and Rhizopus in decreasing sequential order. Aspergillus flavus had the highest individual count in melon seed from both zones. Aflatoxin B1 was detected at levels above 5 microg/kg in 32.2% of samples, while only 3.5% of the samples contained the toxin above the 20 microg/kg Nigerian tolerance level in food. The percentage of samples contaminated with aflatoxin B1 was statistically comparable for the pooled data of villages and towns. The median level of aflatoxin B1 was less than 5 microg/kg in the seed samples, while the mean aflatoxin B1 levels was 14.1 microg/kg in the forest and 13.0 microg/kg in the savanna samples.

Aflatoxin B1↗

PubMed2005

Immunohistochemical study of proliferating cell nuclear antigen (PCNA) in duckling liver fed with aflatoxin B1 and esterified glucomannan.

The effect of esterified glucomannan on aflatoxin B(1) toxicity in ducklings was studied by immunohistochemical staining of proliferating cell nuclear antigen (PCNA) in hepatic cells on formalin-fixed paraffin-embedded liver samples. Cherry Valley ducklings were divided into five groups, 20 birds in each. One of the groups was fed with conventional feed, and the other groups were fed with diet containing 100 ppb aflatoxin B(1), that containing 0.05% esterified glucomannan, or that containing 100 ppb aflatoxin B(1) supplemented with 0.05 or 0.1% esterified glucomannan, from five days of age for one month, and subsequently all the groups were fed with conventional feed for 20 days. Four birds of each group were sacrificed on the 30th, 35th, 40th, 45th and 50th day of feeding, and PCNA on the liver tissue sections was quantitatively analyzed by immunohistochemical staining. The percentage of PCNA-positive hepatocytes was significantly higher in the group given diet containing aflatoxin B(1) than in the other groups, which were not significantly different from each other. The results demonstrate that supplementation of feed with esterified glucomannan is effective in reduction of aflatoxin B(1)-induced hepatic injury in ducklings.

Aflatoxin B1↗

PubMed2001

Determination of aflatoxins B1, B2, G1 and G2 in spices using a multifunctional column clean-up.

A rapid and simple method using a multifunctional column, which contains lipophilic and charged active sites, was developed to analyse aflatoxins B1, B2, G1 and G2 in various spices, such as red pepper and nutmeg. After extraction by acetonitrile:water (9:1) and clean-up using MultiSep #228 column, the aflatoxins and aflatoxin-TFA derivatives are determined using LC with fluorescence detection. Recoveries of each aflatoxin B1, B2, G1 and G2 spiked to red pepper, white pepper, black pepper, nutmeg and tear grass at the level of 10 ng/g were over 80-85% in all instances. The minimum detectable concentration for aflatoxins in red pepper was 0.5 ng/g.

Aflatoxins↗

PubMed2003

Determination of aflatoxins in peanuts by matrix solid-phase dispersion and liquid chromatography.

A new method based on matrix solid-phase dispersion (MSPD) extraction was studied to determine aflatoxin B1, B2, G1 and G2 from peanuts. Optimization of different parameters, such as type of solid supports for matrix dispersion and elution solvents were carried out. The method used 2 g of peanut sample, 2 g of C18 bonded silica as MSPD sorbent and acetonitrile as eluting solvent. Recoveries of each aflatoxin spiked to peanut samples at 2.5 ng/g (5 ng/g for aflatoxin G2) level were between 78 and 86% with relative standard deviations ranging from 4 to 7%. The limits of quantification ranged from 0.125 to 2.5 ng/g for the four studied aflatoxins using liquid chromatography (LC) with fluorescence detection. In addition, LC coupled to mass spectrometry with an electrospray interface was used for confirmation of aflatoxins present in real samples. Eleven peanut samples from different countries were analyzed by the proposed method and by using an enzyme-linked immunosorbent assay (ELISA). ELISA test is a good screening method for investigation of these mycotoxins in peanut samples.

Aflatoxins↗

PubMed1998

Stability and determination of aflatoxins by high-performance liquid chromatography with amperometric detection.

A method based on reversed-phase high-performance liquid chromatography (RP-HPLC) with amperometric detection with a glassy carbon electrode at a constant potential of 1.4 V is reported for the separation and identification of aflatoxins B1, B2, G1 and G2 in a model mixture. The chromatography was performed on a PAH-Baker column with a ternary mobile phase containing methanol, acetonitrile and aqueous LiClO4 electrolyte. Aflatoxin G1 showed the highest electroactivity in the compound series studied. Calibration curves of aflatoxins G1 and B2 were linear up to 0.2 and 0.3 mmol/l, respectively. Sensitivity varied between 7 and 10 ng for the different aflatoxins. The combination of different HPLC detectors in the analysis of these compounds was applied to investigate the stability of aflatoxins G1 and B2.

Aflatoxins↗