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PubMedDate not supplied

Interactive effects of duration of storage and addition of formaldehyde on levels of aflatoxin M1 in milk.

Spray-dried skim milk, naturally contaminated with aflatoxin M1, was added to either raw or pasteurized whole milk to a final concentration of 1.1 microgram aflatoxin M1/L milk. Formalin (37% w/w) was added to the milk solutions to final concentrations of 0, 0.025, 0.05, and 0.1% formaldehyde. Samples were stored in the dark at 21 degrees C in plastic and glass containers and were analyzed for aflatoxin M1 at 0, 1, 2, 3, and 4 weeks. This experiment was repeated using only raw milk and glass containers. Aflatoxin M1 analyses were done at 0, 1, and 2 weeks. Aflatoxin M1 losses increased over time and with increased formaldehyde concentration. With both experiments, aflatoxin M1, levels after 2 weeks were less than 0.05 micrograms/L in samples containing 0.1% formaldehyde.

Aflatoxin M1↗

PubMed1987

Effects of hydrogen ion and fatty acid concentrations on the binding of aflatoxin B1 to human albumin.

The influence of pH and long-chain fatty acids on the interaction between aflatoxin B1 and human albumin was investigated by fluorescence spectroscopy. Both the binding of aflatoxin B1 to albumin and the fluorescence of albumin-bound aflatoxin are pH-dependent over the pH range of 6-9.5. The data indicates that the carcinogen has a higher affinity for the basic(B) than for the neutral(N) conformation of human albumin. Palmitic, stearic and oleic acids up to a molar ratio of 2 over albumin, increases the binding strength of aflatoxin B1 by means of an allosteric mechanism. Furthermore, the pH-dependence of the aflatoxin-albumin interaction is affected by the presence of oleic acid by narrowing the pH range over which the dependence occurs. At molar ratios of oleic acid to albumin in excess of 4.25 at pH6, 3.1 at pH7.4 and 2.4 at pH9 cause a decrease in aflatoxin B1 fluorescence as a result of reduced binding to albumin.

Aflatoxin B1↗

PubMed1988

[Determination of aflatoxin B1 in dried figs by visual screening, thin-layer chromatography and ELISA].

Aflatoxin B1-contaminated fruits were sorted out from 250 kg dried figs (five Turkish and three Greek batches) by bright-greenish-yellow fluorescence under UV light. The aflatoxins of the fluorescent figs were extracted by simple soaking in methanol. Aflatoxin B1 was determined by thin-layer chromatography. Parallel to this, an extraction for the determination of aflatoxin B1 was developed by a competitive ELISA and the two methods were compared with each other. In a highly contaminated batch of Turkish figs, statistically there was one fig among 350 which had a high aflatoxin content (greater than 100 ng/g fig) and one fig amongst 140 fruits with an aflatoxin B1 content of greater than 10 ng B1/g fig.

Aflatoxin B1↗

PubMedDate not supplied

Effect of dietary exposure to aflatoxin B1 on resistance of young chickens to organophosphate pesticide challenge.

White leghorn chickens were placed on a diet containing 0, 1000, or 3000 ppb aflatoxin B1 for 7 weeks. At the end of that time, the birds were challenged orally with the organophosphate pesticide malathion. A malathion dose of 215 mg/kg resulted in significant clinical signs of cholinergic poisoning in 4/10, 5/10, and 8/10 birds fed 0, 1000, and 3000 ppb aflatoxin B1, respectively, and the chickens required antidotal atropine 40 min later. Activity of brain cholinesterase was significantly lower than control levels in all birds given this dose of malathion, with activities being 28% +/- 6, 21% +/- 2, and 15% +/- 2 of control values (Mean +/- standard error, N = 5) if fed 0, 1000, and 3000 ppb aflatoxin B1, respectively. Plasma cholinesterase values paralleled those of brain, with significantly more inhibition in samples from birds given 1000 and 3000 ppb aflatoxins with malathion. Brain and plasma cholinesterase activities in birds fed aflatoxins and given a dose of malathion below the threshold for cholinergic signs (125 mg/kg) were also lower than activities in birds given malathion alone. Although aflatoxin alone had no direct effect on the activities of these enzymes, it appears that this mycotoxin may contribute to the esterase inhibition that is a manifestation of the acute toxic effects of malathion in chickens.

Aflatoxin B1↗

PubMed1983

[Determination of aflatoxin M1 in milk and proof of its toxicity in chick embryos].

Out of 67 milk samples analyzed in the spring 1980, nine samples contained 0.05 to 0.10 microgram . 1(-1) of M1 aflatoxin. Fifty samples analyzed in the spring 1982 contained no M1 aflatoxin. The toxicity of M1 aflatoxin determined in two-, three- and four-day chick embryo amounted to 0.10 microgram, the toxicity of B1 aflatoxin to 0.014 microgram per embryo. On the basis of M1 aflatoxin content in milk and its toxicity it can be presumed that with the current fodder base for dairy cows no toxic effect of M1 aflatoxin in milk and milk products is to be expected.

Aflatoxin M1↗

PubMed1982

Quantitation of aflatoxin B1-modified DNA using monoclonal antibodies.

Five monoclonal antibodies were obtained after fusion of mouse P3 x 63 myeloma cells with spleen cells isolated from BALB/c mice that had been immunized with aflatoxin B1-adducted DNA complexes with methylated bovine serum albumin. Selected hybridomas were found to produce monoclonal antibodies specific for modified DNA containing both the 2,3-dihydro-2-(N7-guanyl)-3-hydroxyaflatoxin B1 and the putative 2,3-dihydro-2-(N5-formyl-2',5',6'-triamino-4'-oxo-N5-pyrimidyl)-3-hydroxyaflatoxin B1, suggesting that these DNA adducts share a common antigenic determinant. Enzyme immunoassay conditions using these monoclonal antibodies were optimized, and DNA isolated from the livers of rats given dosages of aflatoxin B1 ranging from 0.01 to 1.0 mg aflatoxin B1 per kg body weight was tested. A level of modification in DNA of 1 aflatoxin B1 residue per 1,355,000 nucleotides can be quantitatively measured. Monoclonal antibodies will be useful probes for studying the molecular interactions of aflatoxin B1 with DNA and the occurrence of aflatoxin B1:DNA adducts in tissues and cells of humans exposed to this environmental carcinogen.

Aflatoxin B1↗

PubMed1982

Enhanced hepatotoxicity of aflatoxin B1 by pretreatment of rats with ethanol.

Hepatotoxicity of aflatoxin B1 (2.0 and 4.0 mg/kg i.p.) as determined by plasma enzyme activities (GPT and GOT), liver triglycerides and histopathologic changes was enhanced in rats pretreated with four oral doses of ethanol (4.0 g/kg each) at 48, 45, 24 and 21 hrs prior to aflatoxin B1 administration. Pretreatment with ethanol (4.0 g/kg) slightly increased liver weight without changing hepatic microsomal protein contents. Also it caused an increase in microsomal aniline hydroxylase but a decrease in p-nitroanisole-o-demethylase, 48 hrs after the first ethanol dose. In the rats pretreated with ethanol, aflatoxin B1 was metabolized at a higher extent to aflatoxins M1 and Q1. These results suggest that an increased hepatotoxicity of aflatoxin B1 after pretreatment with ethanol may presumably due to an increase in microsomal formation of active aflatoxin B1 metabolite.

Aflatoxin B1↗

PubMedDate not supplied

Enzyme-linked immunosorbent assay of total aflatoxins B1, B2, and G1 in corn: follow-up collaborative study.

A direct competitive enzyme-linked immunosorbent assay screening method for aflatoxins at 20 ng/g in corn was studied by 15 collaborating laboratories. Test samples of corn were extracted by blending with methanol-water (8 + 2). The extracts were filtered and the filtrates were diluted with buffer to a final methanol concentration of < 30%. Each diluted filtrate was applied to a test device containing a filter with immobilized polyclonal antibodies specific to aflatoxins B1, B2, and G1. Aflatoxin B1-peroxidase conjugate was added, the test device was washed with water, and a mixture of hydrogen peroxide and tetramethylbenzidine was added. A test sample was judged to contain > or = 20 ng aflatoxins/g when, after exactly 1 min, no color was observed on the filter; if a blue or gray color developed, the test sample was judged to contain < 20 ng aflatoxins/g. All laboratories correctly identified naturally contaminated corn test samples. Only one false positive was found for controls containing no aflatoxins. The correct responses for positive test samples spiked at levels of 10, 20, and 30 ng aflatoxins/g (the ratio of B1:B2:G1 was 15:1:3) were 67, 97, and 100%, respectively. This method was adopted first action by AOAC INTERNATIONAL as a change in method for 990.34 for screening for aflatoxins B1, B2, and G1 in corn at total aflatoxin concentrations of > or = 20 ng/g.

Aflatoxin B1↗

PubMed1995

Aflatoxin-producing potential of Aspergillus flavus and Aspergillus parasiticus isolated from samples of smoked-dried meat.

Over a period of three years 420 samples of various smoke-dried meat products, collected from individual households in different region of Croatia were analysed for the presence of aflatoxigenic strains of the Aspergillus flavus group. Strains of A. flavus and A. parasiticus were present in 17.8% of the samples, and aflatoxin-producing ability was tested in 75 strains. In relation to sequential method of aflatoxin detection, 5 of 8 isolates were found in the first step (fluorescence in aflatoxin-producing ability medium--APA) and all of them in the second step (extraction method from syntheses on moist shredded wheat--SW). A. flavus strains produced mainly aflatoxin B1, and had various levels of toxigenicity (1.4-3.12 mg/kg). Some strains of A. parasiticus produced all four aflatoxins B1 B2 G1 G2, while the other ones produced AF B1 + G1 only, with concentrations of aflatoxins from 0.1 to 450 mg/kg.

Aflatoxins↗

PubMed1997

Influence of white light, near-UV irradiation and other environmental conditions on production of aflatoxin B1 by Aspergillus flavus and ochratoxin A by Aspergillus ochraceus.

The effects of illumination, near-ultraviolet, incubation temperature pH and some minor elements on the growth rate and production of aflatoxin B1 by A. flavus and ochratoxin A by A. ochraceus were investigated. Aflatoxin B1 and ochratoxin A production was considerably higher in the light than in the dark. The greatest aflatoxin B1 and ochratoxin A production was occurred after 11 days of fermentation with light- and dark-grown cultures at 25 degrees C. The mycelial dry weight was also greater in the light than in the dark for both A. flavus and A. ochraceus. Exposure of conidia to near-UV irradiation increased mycelial dry weight and mycotoxins by both fungi more than white light. The greatest aflatoxin B1 and ochratoxin A was at 25 degrees C with UV-grown culture (24 h exposure) producing a mean of 400 and 260 micrograms/50 ml of medium, respectively. The maximum aflatoxin B1 and ochratoxin A yield was obtained at pH 5.5 and with increasing the initial pH to near neutrality, both mycotoxins yield decreased. Iron, copper and zinc were observed to stimulate aflatoxin B1 and ochratoxin A production and enhanced the growth rate of both A. flavus and A. ochraceus.

Aflatoxin B1↗

PubMedDate not supplied

Distribution of aflatoxins between extract and extraction residue of paprika using supercritical carbon dioxide.

Paprika powder, naturally contaminated with aflatoxins, was extracted by supercritical carbon dioxide at standard conditions (300 bar and 50 degrees C). A lipophilic top phase and an aqueous base phase were obtained. These and the extraction residue were analysed by HPLC for aflatoxins. The main quantity of aflatoxins, about 60% of aflatoxin B1 and about 70% of aflatoxin B2 related to the original paprika powder, was found to be located in the extraction residue. This confirms the results of previous studies with other spices and demonstrates that the use for flavouring purposes of supercritical carbon dioxide extracts, rather than natural spice, offers potential application in reducing aflatoxin levels in spiced foods.

Aflatoxins↗

PubMed2002

Aflatoxin, hepatitis and worldwide liver cancer risks.

Aflatoxins are among the most potent mutagenic and carcinogenic substances known. Differential potency of aflatoxin among species can be partially attributed to differences in metabolism; however, current information on competing aspects of metabolic activation and detoxification of aflatoxin in various species does not identify an adequate animal model for humans. Risk of liver cancer is influenced by a number of factors, most notably carriage of hepatitis B virus as determined by the presence in serum of the hepatitis B surface antigen (HBsAg+ or HBsAg-). About 50 to 100% of liver cancer cases are estimated to be associated with persistent infection of hepatitis B (or C) virus. The potency of aflatoxin in HBsAg+ individuals is substantially higher (about a factor of 30) than the potency in HBsAg- individuals. Thus, reduction of the intake of aflatoxins in populations with a high prevalence of HBsAg+ individuals will have greater impact on reducing liver cancer rates than reductions in populations with a low prevalence of HbsAg+ individuals. The present analysis suggests that vaccination against hepatitis B (or protection against hepatits C), which reduces prevalence of carriers, would reduce the potency of the aflatoxins in vaccinated populations and reduce liver cancer risk.

Aflatoxins↗

PubMed1984

Defenses against aflatoxin carcinogenesis in humans.

Aspects of work on aflatoxin mainly from the author's studies are discussed, emphasizing procedures, strategies and insights related to protection against aflatoxin carcinogenesis in man due to transmission in the food chain. Five lines of defense are discussed. First, is the interfacing of the farm animal as a biologic filter between contaminated crop (feed) and human food derived from animal products. Second, is chemical detoxification of meals with ammonia and of contaminated milk by ultraviolet light. Third is prevention of mold growth and aflatoxin elaboration with ammonium carbonate for potential application during storage and drying of agricultural products. Fourth, is the development of ultrasensitive analytical methods for aflatoxins with structural proof of identity. And, fifth are natural defenses related to the role of hydroxylation of mammalian metabolism in detoxification, especially the pathway to aflatoxin Q1, a major detoxifying mechanism in primates, and the epoxidation pathway and its relation to prevention of aflatoxin residue transmission into edible tissues.

Aflatoxins↗

PubMed1984

Effect of phytate on aflatoxin formation by Aspergillus parasiticus and Aspergillus flavus in synthetic media.

The effect of phytate on the production of aflatoxins by Aspergillus parasiticus and Aspergillus flavus grown on synthetic media was examined. In the absence of pH control (initial pH 4.5-6.5) for A. parasiticus, phytate (14.3 mM) caused a six-fold decrease in aflatoxins in the medium and a ten-fold decrease in those retained by the mycelia. When the initial pH of the medium was adjusted to 4.5 no effect on aflatoxin production was observed. With A. flavus or A. parasiticus grown on media with a higher initial pH value (6 to 7), the presence of phytate in the media caused an increase in aflatoxin production. These results are inconsistent with previous studies which indicated that phytate depresses aflatoxin production by rendering zinc, a necessary co-factor for aflatoxin biosynthesis, unavailable to the mold.

Aflatoxins↗

PubMed1985

Winged bean (Psophocarpus tetragonolobus (L.) DC) as a substrate for growth and aflatoxin production by aflatoxigenic strains of Aspergillus spp.

The mold flora of seeds of twelve varieties of winged beans was determined both before and after surface disinfections. When seeds were surface disinfected, mold fungi were detected in 73% of the seeds whereas 81% of the seed that was not disinfected produced mold fungi. Aspergillus spp. was most frequently present while Penicillium spp. occurred in seed of 4 varieties and in less than 4% of the seed. Twelve isolates of A. flavus and A. parasiticus were examined for their ability to produce aflatoxins. Whether aflatoxins were produced and the amount of each varied according to the origin of the isolate and the species of Aspergillus. For example all A. parasiticus isolates produced at least 2 aflatoxins whereas 4 of the A. parasiticus isolates were non-toxigenic. When ground seeds of winged beans were inoculated with an aflatoxigenic strain of A. parasiticus the level of aflatoxins that occurred varied with the variety, however, the level of aflatoxin was higher in winged bean than in peanut tissue and 6 of the 12 winged bean varieties contained higher levels of aflatoxins than rice.

Aflatoxins↗

PubMed1983

Aspergillus infection and aflatoxin production in some cowpea (Vigna unguiculata (L.) Walp) lines in Tanzania.

Seeds of twenty-two cowpea (Vigna unguiculata (L.) Walp) lines/cultivars were inoculated with Aspergillus parasiticus (Link) (NRRL 3145) and aflatoxin production was evaluated. All the cowpea samples were susceptible to Aspergillus infection and subsequent aflatoxin production. The amount of aflatoxin produced ranged between 466.6 micrograms/kg to 1 806 micrograms/kg in the case of B (B1 + B2) and 20.8 micrograms/kg to 82.7 micrograms/kg of seed in the case of G (G1 + G2). On the basis of the amount of aflatoxin produced on different samples, it is evident that there is at least partial resistance to aflatoxin production in the tested cowpea lines/cultivars. On the basis of the results obtained in this investigation it is apparent that further selection and breeding could provide cowpea cultivars which are resistant to A. parasiticus infection and aflatoxin production.

Aflatoxins↗

PubMed1986

Winged bean (Psophocarpus tetragonolobus (L.) DC) as a substrate for growth and aflatoxin production by aflatoxigenic strains of Aspergillus spp.

The mold flora of seeds of twelve varieties of winged beans were determined both before and after surface disinfections. When seeds were surface disinfected, molds were detected in 73% of the seeds whereas 81% of the seed that was not disinfected produced molds. Aspergillus spp. were most frequently present while Penicillium spp. occurred in seed of 4 varieties and in less than 4% of the seed. Twelve isolates of A. flavus and A. parasiticus were examined for their ability to produce aflatoxins. Whether aflatoxins were produced and the amount of each varied according to the origin of the isolate and the species of Aspergillus. For example all A. flavus isolates produced at least 2 aflatoxins whereas 4 of the A. parasiticus isolates were nontoxigenic. When ground seeds of winged beans were inoculated with an aflatoxigenic strain of A. parasiticus the level of aflatoxins that occurred varied with the variety. All of the varieties supported greater aflatoxin production than peanuts and 6 of the 12 winged bean varieties gave higher levels of aflatoxins than rice.

Aflatoxins↗

PubMed1985

Effect of phytate on aflatoxin formation by Aspergillus parasiticus grown on different grains.

Aflatoxin production by Aspergillus parasiticus on corn, soybean, and cottonseed in the absence or presence of added sodium phytate was examined. No variation in aflatoxin concentrations was found in raw, chemically sterilized, or autoclaved soybeans whereas a five-fold reduction in total aflatoxins was found in cottonseed after addition of 330 micrograms sodium phytate to 10 g of autoclaved material. However, phytate did not affect aflatoxin production on non-sterile cottonseeds, although in corn a slight inhibition was found. Extraction of raw soybeans with hexane allowed production of 20-fold more aflatoxins, but levels were still lower than those found on rice or corn. Part of this relative inhibition in soybeans may arise from a heat-unstable, polar solvent-soluble, dialyzable factor present in soybeans. Our results support the conclusion that phytate is not the factor in soy responsible for its relative resistance to aflatoxin formation.

Aflatoxins↗