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PubMed1992

Development and evaluation of analytical methodology for the determination of aflatoxins in palm kernels.

A rapid, simple and reproducible method for the simultaneous estimation of aflatoxins AFB1, AFB2, AFG1 and AFG2 in palm kernel samples has been developed by optimizing the sample preparation, solvent extraction, sample clean-up and quantification procedures. The aflatoxins are extracted from a slurried palm kernel sample with an acetone-water (80 + 20, v/v) mixture and the crude extract is cleaned up by solid-phase extraction using a phenyl bonded phase cartridge. The extract is passed through the cartridge with a water-methanol (93 + 7) mixture. Subsequent elution of the aflatoxins retained on the cartridge is achieved with a 3 ml aliquot of chloroform. The aflatoxin content of the eluate is quantified using a bi-directional high-performance thin-layer chromatography procedure. A critical evaluation of the proposed method was carried out by statistical comparison with the British Standard Method. The proposed procedure was shown to be more efficient and precise. Consistent recoveries of over 90% were achieved from spiked palm kernel extracts and detection limits were found to be 3.7, 2.5, 3.0 and 1.3 micrograms kg-1 for AFB1, AFB2, AFG1 and AFG2 aflatoxins, respectively.

Aflatoxins↗

PubMed2001

Phage-displayed peptides that mimic aflatoxin B1 in serological reactivity.

AIMS: To test phage-displayed random peptide libraries as sources of peptides that mimic the binding of aflatoxin B1 to monoclonal antibodies raised against the toxin. METHODS AND RESULTS: For two of the three MAbs tested, clones were obtained by panning, producing phage that bound specifically to MAb 13D1-1D9 (MAb 24; specific for aflatoxins B1 and G1) and MAb 6E12-1E9 (MAb 13; specific for aflatoxins B1, G1 and B2) in ELISA. The amino acid sequences of the binding peptides varied. Those binding to MAb 24 contained the sequence of '...YMD...', and those that bound to MAb 13 contained the dipeptide 'PW'. Mimotope phage was used in a competition ELISA format for assaying aflatoxin concentrations. CONCLUSION: The results show that mimotope preparations are effective substitutes for pure toxin in these ELISA procedures. SIGNIFICANCE AND IMPACT OF THE STUDY: These results should contribute significantly to enhancing the safety and diminishing the costs of aflatoxin assays.

Aflatoxin B1↗

PubMed2000

Calmodulin mediated activation of acetyl-CoA carboxylase during aflatoxin production by Aspergillus parasiticus.

The relevance of Ca2+-calmodulin-mediated processes in channelling acetate for aflatoxin formation was investigated by studying the influence of trifluoperazine (an anticalmodulin agent) on [14C]-acetate incorporation and activity of acetyl-CoA carboxylase in Aspergillus parasiticus NRRL 2999. Culturing the organism in presence of 0.14 mmol l-1 trifluoperazine resulted in 55% decrease of [14C]-acetate incorporation into aflatoxin B1, along with an 80% decrease in acetyl-CoA carboxylase activity at periods corresponding to maximal aflatoxin production. Concomitant decrement (35%) in the activity of glucose-6-phosphate dehydrogenase indicated decreased availability of reduction potential (NADPH) required for aflatoxin biosynthesis. The ability of calmodulin to activate and trifluoperazine to inhibit acetyl-CoA carboxylase activity in a dose-dependent manner was also noted under in vitro conditions. The combined results suggest calmodulin-mediated activation of acetyl-CoA carboxylase as an important event for aflatoxin production.

Acetates↗

PubMed1978

Modification of DNA by aflatoxin B1 creates alkali-labile lesions in DNA at positions of guanine and adenine.

The damage to DNA by the hepatocarcinogen aflatoxin B1 was investigated. A DNA fragment of known sequence of the lactose promoter-operator region was used as a substrate for modification by aflatoxin B1. The DNA was incubated with aflatoxin B1 in crude mammalian liver extracts or with purified microsomes. Treatment of the DNA incubated in the complete system with either 1 M piperidine or 0.1 M NaOH at 90 degrees revealed alkali-labile lesions in the DNA. The exact location of the cleavage site was determined by comparison of the length of the cleavage products with the known sequence on polyacrylamide gels. The lengths of the cleavage products were the same as those produced by alkali-induced breakage of the same sequence of DNA that had been modified with dimethyl sulfate. The major cleavage products of the aflatoxin B1-modified DNA were at positions of guanine and the minor cleavage products were at positions of adenine. These studies show that modification of DNA by aflatoxin B1 creates alkali-labile sites at positions of guanine and, to a lesser extent, adenine.

Aflatoxins↗

PubMed1997

Aflatoxin B1 epoxidation catalysed by partially purified human liver lipoxygenase.

(1) This study demonstrates for the first time the human liver lipoxygenase-mediated co-oxidation of aflatoxin B1 to the reactive metabolite, aflatoxin B1-8,9-epoxide, which rapidly hydrolyzes to dihydrodiol and preferentially binds to Tris. (2) The Tris-diol complex formed was quantitated fluorimetrically, based on its characteristic excitation at lambda ex = 395 nm and emission at lambda em = 435 nm. (3) The incubation of partially purified human liver lipoxygenase for 30 min under optimum assay conditions (3.5 mM linoleic acid and 50 microM aflatoxin B1 in Tris buffer at pH 7.2) resulted in the formation of 10.6 +/- 1.7 nmol Tris-diol/mg protein. (4) In addition to linoleic acid, other unsaturated fatty acids namely gamma-linolenic acid, cis-11, 14-eicosadienoic acid and arachidonic acid also supported the lipoxygenase mediated epoxidation of aflatoxin B1. (5) The enzymatic Tris-diol formation was significantly inhibited by all the lipoxygenase inhibitors tested in a concentration-dependent manner. (6) These results strongly suggest that lipoxygenase is capable of aflatoxin B1 metabolism and this may represent yet another pathway for the bioactivation of this hepatocarcinogen in the human liver.

Aflatoxin B1↗

PubMed1997

Aflatoxins in the lungs of children with kwashiorkor and children with miscellaneous diseases in Nigeria.

Autopsy lung specimens from 20 children with kwashiorkor and 20 with other miscellaneous diseases, at the Obafemi Awolowo Teaching Hospital complex, Ile-Ife, Nigeria, were analyzed for the presence of aflatoxin using high-performance liquid chromatography. Aflatoxins were detected in 18 children who died from kwashiorkor but only in 13 of those who died from miscellaneous diseases. Of the 10 children, 5 in each group, who died with pneumonia, all had detectable levels of aflatoxins in their lungs. The two children with congestive cardiac failure, one secondary to pneumonia and the other secondary to tuberculous pericarditis, had more than two detectable aflatoxins in their lungs. These findings demonstrate that Nigerian children are exposed to aflatoxins and that high levels can accumulate in lung tissue.

Adolescent↗

PubMed1983

Aflatoxin as a cause of primary liver-cell cancer in the United States: a probability study.

Primary liver-cell cancer (PLC) mortality ratios, computed from death certificate records compiled by the National Center for Health Statistics, for the periods 1968-1971 and 1973-1976 were sorted by race, sex, urbanization, and region. From this sort, rural white males from the Southeast and the "North and West" regions were selected for comparison of mortality ratios and past dietary exposure to aflatoxin. Based on projections of recent aflatoxin contamination information back to the 1910-1960 period, and estimates of corn and peanut usage from household food consumption surveys relating to that period, the expected average daily ingestion of aflatoxin B1 for each group was calculated (Southeast, 13-197 ng/kg bw; North and West, 0.2-0.3 ng/kg bw). An age-adjusted excess PLC mortality ratio was observed for the Southeast population when compared with the "North and West"-10% excess PLC deaths at all ages, and 6% excess PLC deaths for the 30-49 year age-group-but although the difference was in the expected direction in relation to projected past exposure to aflatoxin, it was far from the manyfold difference that would have been anticipated from experiments with rats and from prior epidemiological studies in Africa and Asia. The remaining major portion of the PLC mortality in the Southeast may be attributed to many unidentified causes for which the two populations that were compared were not controlled, leaving in doubt the validity of any attribution of the excess PLC mortality to aflatoxin ingestion. A considerable excess over average US PLC mortality ratios was seen for all Orientals resident in the US and for urban black males. Occurrence of PLC in Orientals has been related to the presence of markers for hepatitis B virus in the blood serum of affected individuals.

Adolescent↗

PubMed1998

Aflatoxin and liver cancer in Sudan.

This study investigated whether aflatoxin contamination of peanut products may contribute to the incidence of hepatocellular carcinoma (HCC) in Sudan. Thirty-seven peanut butter and peanut samples were collected from local markets. Aflatoxin concentrations were significantly higher in West Sudan [87.4 +/- 197.3 (SD) micrograms/kg], a high-risk area, than in Central Sudan (8.5 +/- 6.8 micrograms/kg), a low-risk area. In West Sudan, humid local storage conditions of peanut products were related to high aflatoxin concentrations. In a small case-control study of HCC patients (n = 24) and controls (n = 34), an odds ratio of 7.5 (95% confidence interval = 1.4-40.2) was observed for humid vs. dry local storage conditions. Development of an index of individual HCC exposure was less successful, probably because of year-to-year variability in aflatoxins in food. These preliminary findings justify further research into the role of aflatoxins and hepatitis in HCC incidence in Sudan.

Adult↗

PubMed2001

A survey of ethnic foods for microbial quality and aflatoxin content.

A range of ethnic foods was examined for their microbiological content in relation to total viable counts (TVC) of aerobic bacteria, counts of presumptive coliforms, yeast and mould counts; presence of Salmonella spp., Listeria monocytogenes, Escherichia coli O157:H7 and Campylobacter spp.; total enumeration of Clostridium perfringens, Staphylococcus aureus and Bacillus spp.; identification of moulds and the presence of total aflatoxins. Samples, which included cereals, nuts, dried fruits, herbs and spices, were obtained from local retail outlets and distributors. It was established that three samples of pistachio nuts contained significant levels of aflatoxins. The concentration of total aflatoxins in these three nut samples ranged from 15 to 259 microg/kg of sample. Only two other samples contained trace amounts of aflatoxins, all other samples analysed were found to be free of any detectable level of aflatoxins. TVCs, coliform counts and yeast and mould counts varied widely depending on the matrix tested. Generally, rice, wheat and peanuts produced low counts whereas other nuts, gram flour and spices produced much higher counts. Cl. perfringens, Staph. aureus, and Bacillus spp. were common in spices, nuts and gram flour, however, Listeria monocytogenes was only detected in four samples and in no sample could Salmonella spp, E. coli O157:H7 or Campylobacter spp. be detected.

Aflatoxins↗

PubMed2000

Survey for aflatoxins, ochratoxin A, zearalenone and fumonisins in maize imported into the United Kingdom.

This survey examined 140 samples of raw maize as received at ports or at major maize mills in the UK and 12 after initial cleaning. Samples were examined for aflatoxins B1, B2, G1 and G2, ochratoxin A, zearalenone and fumonisins B1, B2 and B3 using fully validated analytical HPLC methods with detection limits of 0.1 microgram/kg for each aflatoxin and ochratoxin A, 4 micrograms/kg for zearalenone and 10 micrograms/kg for each fumonisin. 95.0% and 92.1% of samples met the new EC statutory maximum permissible level for total aflatoxins and aflatoxin B1 respectively. The maximum concentration of ochratoxin A found was 1.5 micrograms/kg. Zearalenone and fumonisins were detected in almost every sample with 41.7% of maize containing more than 100 micrograms/kg of zearalenone and 48% of samples containing more than 1000 micrograms/kg total fumonisins. Initial cleaning of raw maize reduced aflatoxin concentrations by about 40% and total fumonisins by 32%.

Aflatoxins↗

PubMedDate not supplied

The effect of feeding aflatoxin-contaminated groundnut meal, with or without ammoniation, on the development of gamma-glutamyl transferase positive lesions in the livers of Fischer 344 rats.

The detoxification of aflatoxin-containing groundnut meal by ammoniation has been investigated using weanling male and female Fischer 344 rats. Rats were fed a pelleted diet consisting of 75% groundnut meal and 25% powdered rat diet, with vitamin supplement, for a period of 90 days. The groundnut meal was either aflatoxin-free or naturally contaminated with aflatoxins, and was used untreated or after ammoniation. Body weights and food consumptions were monitored throughout the experimental feeding period. After 90 days the animals were sacrificed and the gamma-glutamyl transferase (GGT) levels in the livers assayed fluorimetrically, and the distribution of the enzyme activity determined histochemically. The results indicated that ammoniation of the aflatoxin-containing meal eliminated the development of focal GGT positive lesions in both male and female animals. However, in the female, histochemical GGT staining of hepatocytes in the periportal areas was increased by all the experimental diets compared with the unammoniated, aflatoxin-free diet. This observation was supported by the fluorimetric assays. Ammoniation of the diet led to a decreased body weight gain in all cases compared with the corresponding unammoniated diet-fed groups.

Aflatoxins↗

PubMedDate not supplied

The occurrence of aflatoxins in peanuts imported into Czechoslovakia for human consumption.

Results of 492 analyses for aflatoxin in raw shelled peanuts imported into Czechoslovakia during 1982-1984 are presented. Most samples (55.3%) had aflatoxin content less than the detection limit of the radioimmunochemical screening method (0.8 micrograms/kg). Further analyses showed that 239 out of 410 samples of roasted peanuts contained aflatoxin below the detection limit. Only 1.9% of all peanut samples were found to have contamination level more than 5 micrograms/kg aflatoxin. The highest levels of aflatoxin observed were in a raw peanut sample containing 202.1 micrograms/kg and in a roasted peanut sample containing 32.6 micrograms/kg.

Aflatoxins↗

PubMedDate not supplied

HPLC determination of the total content of aflatoxins in naturally contaminated eggs in free and conjugate forms.

A study was undertaken to evaluate the total aflatoxin content in naturally contaminated eggs. Two pools of eggs from laying hens were collected after 2 and 7 days of treatment with aflatoxin B1 (AFB1). An HPLC method has been developed for the determination of AFB1, aflatoxin M1 (AFM1), aflatoxin B2a (AFB2a) and aflatoxicol (Ro) both in free form and after release from water-soluble conjugates. The bound form was cleaned up after acid hydrolysis of the aqueous phase. Eggs collected after 2 days of treatment revealed residues of AFB1, AFB2a and Ro in the organic phase, but none in the aqueous portion. After 7 days of treatment both AFB1 and its hydroxy derivative were found in the organic phase but the aqueous portion showed only hydroxylated metabolites accounting for 35% of the total aflatoxin content.

Aflatoxins↗

PubMedDate not supplied

Monitoring and identification of aflatoxins in wheat, gram and maize flours in Bihar state (India).

The occurrence of aflatoxins in some common food commodities: wheat, gram and maize flours is reported. Of the total 416 collections during three years (1987-1989) 162 were recorded to be aflatoxin-positive. The incidence of aflatoxins was maximum in the samples of 1987. Most of the contaminated samples contained aflatoxins at levels above 20 micrograms/kg. The environmental conditions and traditional agronomic and storage practices relating to aflatoxin incidence are discussed.

Aflatoxins↗

PubMedDate not supplied

Sampling bulk consignments of dried figs for aflatoxin analysis.

The between-box aflatoxin distribution for a bulk consignment of whole dried figs (11 tons) has been established by the individual analysis of 200 boxes (analysed as single samples of 12 kg each of homogenized material) randomly selected from a total of 850 boxes. The within-box aflatoxin distribution for three boxes was investigated by the analysis of 12 subsamples in each case made up of packets of figs totalling 1 kg in weight. Of the 200 boxes, 134 contained less than 10 micrograms/kg total aflatoxins whereas the highest level found was 227 micrograms/kg. The highest level of aflatoxins found in a single 1 kg unit was 2063 micrograms/kg. The batch average aflatoxin contamination determined on the basis of a single 20 kg homogenized sample (20 x 1 kg subsamples) was 33 micrograms/kg, compared to a level of 15 micrograms/kg calculated as the average of 200 determinations. Evaluations are made of different possible ways of sampling and the confidence that can be associated with each of these is estimated.

Aflatoxins↗

PubMedDate not supplied

Present status of the aflatoxin situation in the Philippines.

Aflatoxin research in the Philippines started at the FNRI in 1967 with a survey on the aflatoxin content of various foods. Local researchers from government institutions and academe also conducted studies on the aflatoxin contamination of agricultural crops and their products/by-products. The data indicated that corn and peanuts are the two commodities that contain toxic levels of aflatoxin. Past and current research in the country is documented. Problems and research needs for the surveillance and/or control of aflatoxin contamination are discussed.

Aflatoxins↗

PubMedDate not supplied

Supervising programme of aflatoxins in Mexican corn.

Contamination of maize with aflatoxins was detected in Tamaulipas in 1989 and the Mexican government organized a Supervising Programme to check the maize crop of Tamaulipas from 1989 to 1992. The monoclonal immunoaffinity column method quantified by fluorometry was chosen as the official one. After detecting, in 1989, the first lots of contaminated maize, in 1990 87% of the crop was quarantined and the Supervising Programme was implemented. Laboratories were constructed in each warehouse that received the maize; one chemical analysis for aflatoxins was performed for every 100 tons of maize received and there were around 60,000 analyses in the whole Programme (1989-1993). A random sampling method was applied, taking 2 kg from each truck. In 1991, the contaminated maize was dyed and separated as feed. Decontaminating methods with aluminosilicates and with ammonia were tested, but the cost was high and these practices were abandoned. A Technological Package for the farmers was organized by different institutions: the Ministry of Health, the Ministry of Agriculture, Conasupo, and the government of the State of Tamaulipas. This specified sowing time, insecticides, fungicides, fertilizers, irrigation periods, maize cultivars, etc. and had successful results in the field, in 1992, when lower quantities of total aflatoxins in maize were detected. On the other hand, the aflatoxin combination of maize persisted in storage areas, especially in the last week of July and the first week of August. The aflatoxin maize problem will be solved only when both field and storage contaminations are controlled.

Aflatoxins↗

PubMedDate not supplied

Quantification of aflatoxins in corn distributed in the city of Monterrey, Mexico.

In this study kerneled corn sold and distributed through wholesale outlets in the city of Monterrey, Mexico was analysed. The extraction of aflatoxins was performed with a mixture of methanol/water (80:20) and its derivatization was carried out with trifluoroacetic acid. The analysis was done by high performance liquid chromatography (HPLC) using fluorescence for detection. From the 41 samples analysed, aflatoxins B1 and G1, were found to be present. Aflatoxin B1 concentrations ranged from 5.03 ng/g to 465.31 ng/g, aflatoxin G1 concentrations ranged from 1.59 ng/g to 57.1 ng/g. It was found that 87.8% of the samples were contaminated with aflatoxins: in addition, 58.5% contained levels above Mexican legal limits which are, at present, 20 ng/g.

Aflatoxins↗