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PubMedDate not supplied

Survey of aflatoxins, ochratoxin A, zearalenone, and sterigmatocystin in some Brazilian foods by using multi-toxin thin-layer chromatographic method.

A previously published method for ochratoxin A was evaluated and proved appropriate for simultaneous determination of aflatoxins, ochratoxin A, sterigmatocystin, and zearalenone, with considerable savings in time and reagent costs. The detection limits were 2, 5, 15, and 55 micrograms/kg, respectively. The recoveries and coefficients of variation obtained with artificially contaminated samples were 91-101% and 0-16% for aflatoxin B1, 98-117% and 0-17% for sterigmatocystin, and 96-107% and 0-17% for zearalenone, respectively. The coefficients of variation for naturally contaminated samples (aflatoxins in rice and ochratoxin A in beans) ranged from 0 to 8%. The method was used to survey 296 samples that included 10 cultivars of dried beans, 8 types of corn products, 3 types of cassava flour, and both polished and parboiled rice between May 1985 and June 1986 in Campinas, Brazil. Only aflatoxin B1 (9 samples, 20-52 micrograms/kg), aflatoxin G1 (4 samples, 18-31 micrograms/kg), and ochratoxin A (5 samples, 32-160 micrograms/kg) were found. The average contamination percentage was 4.7%; beans showed the highest (6.6%) and rice showed the lowest (3.3%) incidence rates. Zearalenone and sterigmatocystin were not detected. Positive samples were confirmed by chemical derivatization, corroborated by development in 3 solvent systems.

Aflatoxins↗

PubMedDate not supplied

Aflatoxin, a human carcinogen: determination in foods and biological samples by monoclonal antibody affinity chromatography.

We have used monoclonal antibody technology to produce antibodies that recognize aflatoxins in order to develop noninvasive methods in conjunction with other chemical analytical techniques to monitor human exposure to environmental carcinogens. These methods require the ability to quantitate aflatoxins and their metabolites, including DNA and protein adducts, in readily accessible compartments such as serum and urine. The techniques permit efficient analysis of many samples in a relatively short time. Also, these monoclonal antibody affinity columns have been extremely useful for rapid isolation of aflatoxins from food and grain samples, as well as aflatoxin M1 from milk. Monoclonal antibody affinity methods are nondestructive to the aflatoxin molecule, so the sample aliquot can be used for confirmation. The use of monoclonal antibody preparative affinity columns represents a major, substantive breakthrough for analytical chemists and will be a generally applicable technology for isolation of many different substances.

Aflatoxins↗

PubMed1986

Decreased complement and bacteriostatic activities in the sera of cattle given single or multiple doses of aflatoxin.

Five steers given 1 dose of partially purified aflatoxin at concentrations sufficient to provide 0.2 mg to 0.8 mg of aflatoxin B1 equivalents/kg of body weight were compared with 4 steers given 14 daily doses of 0.25 mg of aflatoxin B1 equivalents/kg of body weight for complement activity and bacteriostasis. Complement activity was measured by hemolysis in gel, and bacteriostatic activity, by growth inhibition of Escherichia coli in liquid medium. In the single-dose group, complement activity and bacteriostatic activities decreased by 57 hours after dosing, and both returned to near base line by 168 hours. In the daily dose group, only bacteriostatic activity decreased, and the decrease persisted 2 weeks after the last dose of aflatoxin was given. Apparently, aflatoxin affects both complement-dependent and independent serum bacteriostatic activity.

Aflatoxins↗

PubMed1987

Incidence of contamination with aflatoxin in precooked corn flour, corn grain and cracked corn.

A study was carried out to determine the presence and content of aflatoxins in 90 samples of precooked corn flour (23 yellow and 67 white), 40 samples of corn grain (30 yellow and 10 white), and 30 samples of yellow cracked corn. No aflatoxin was detected in white corn grain. The other investigated samples showed the following rates of contamination: yellow corn grain, 10%, ranging from less than 5 to greater than 10 ppb; yellow cracked corn, 16.6%, ranging from less than 5 to greater than 20 ppb; and white corn flour, 6%, and yellow corn flour, 87%. Of 14 aflatoxin positive samples tested, only 1 contained more than 20 ppb, the administrative guideline established by the US Food and Drug Administration (FDA). The results of this survey do not appear alarming because of the relatively low incidence and low levels of aflatoxin detected. However, since Venezuela is a big consumer of corn and corn-derived products, a more detailed investigation is suggested to establish the realistic levels of aflatoxin in these commodities.

Aflatoxins↗

PubMed1979

Reduction of mutagenic activity of aflatoxins after UV-irradiation.

Solutions of aflatoxins B1, B2, G1 and G2 and solid films of aflatoxin B1 were irradiated with UV light of wavelength corresponding to the absorption band of aflatoxins at approximately 365 nm (approximately 27 500 cm-1). The reaction was followed spectrophotometrically. Simultaneously the mutagenicity of samples of aflatoxins was determined using Salmonella typhimurium/mammalian microsome test. UV-irradiation caused a modification in all aflatoxins studied (in aqueous and nonaqueous solutions as well as in a solid film); the final photoproducts lost completely the mutagenic activity.

Aflatoxins↗

PubMed1977

Partial characterization of the mode of action of benzoic acid on aflatoxin biosynthesis.

Aflatoxin production by a toxigenic strain of Aspergillus flavus was greatly reduced by benzoic acid and sodium benzoate in synthetic media. The reduction was accompanied by the appearance of a yellow pigment. Spectral analyses partially characterized this pigment as closely related to an acetyl derivative of a versiconal-type compound. A cell-free extract prepared from A. flavus grown in synthetic media was active in converting this yellow compound into aflatoxin B1 in the presence of reduced nicotinamide adenine dinucleotide phosphate at 25 degrees C (pH 7.4). In the presence of benzoic acid and its salt or autoclaved cell-free extract, conversion of yellow compound to aflatoxin B1 was prevented. These results suggest that the yellow compound is an intermediate in the secondary metabolic cycle involved in aflatoxin B1 production. Benzoic acid, sodium benzoate, or autoclaving the cell-free extract appear to have respectively blocked or denatured an enzymatic step late in the biosynthetic pathway of aflatoxin B1.

Aflatoxins↗

PubMed1979

Aflatoxin B1; its role in the etiology of Reye's syndrome.

Seven cases of Reye's syndrome in which aflatoxin B1 was isolated from the blood or liver or both are presented. In two cases aflatoxin B1 was found in the blood during the acute phase of the disease; a finding not previously reported. In six cases aflatoxin B1 was recovered from autopsy specimens of liver. A number of case reports linking aflatoxin B1 to Reye's syndrome have appeared in the literature but until now only one case had been reported from the United States. Aflatoxin B1 and its possible role in the etiology of Reye's syndrome is discussed. It is concluded that Reye's syndrome is the result of multiple interrelated factors.

Aflatoxins↗

PubMed1979

High pressure liquid chromatographic determination of aflatoxins in corn.

A high pressure liquid chromatographic (HPLC) method is proposed for determining aflatoxins in corn. The sample is extracted with methanol-10% NaCl (4 + 1), pigments are precipitated with zinc acetate, and the extract is cleaned up on a small (2 g) silica gel column. Aflatoxins in the purified extract are resolved by normal phase HPLC on a microparticulate (10 micrometer) silica gel column with water-saturated chloroform-cyclohexane, acetonitrile solvent, and detected by fluorescence on a silica gel-packed flowcell. The method was compared with chloroform-water extraction of the official CB method on 15 samples of contaminated corn. In 5 of the 6 samples containing aflatoxins B1, B2, G1, and G2, methanol-10% NaCl extracted more aflatoxin than did cloroform-water, as measured both by HPLC and by thin layer chromatography. In samples containing only B1 and B2, the 2 extraction solvents were virtually equivalent. Agreement was good between HPLC and TLC for each extraction solvent. Average recovery of aflatoxins B1, B2, G1, and G2 added to yellow cornmeal at 3 levels was greater than 90%.

Aflatoxins↗

PubMed1975

Differential inhibition of rat liver sialyltransferase(s) by various aflatoxins and their metabolites.

Sialyltransferase(s) activity [CMP-N-acetylneuraminic acid:glycoprotein sialyltransferase(s) E.C. 2.4.99.1] was assayed using asialofetuin as a substrate in a total microsomal fraction obtained from rat liver. Rats pretreated with phenobarbital or methylcholanthrene demonstrated a decrease in membrane bound sialyltransferase(s) activity of 27% and 18%,respectively. Microsomes prepared from phenobarbital treated rats were incubated in vitro with aflatoxins B1, B2, B2a, G1, or G2 in the presence or absence of an NADPH generating system. Following this treatment the microsomes were reisolated, washed and assayed for sialyltransferase(s) activity. Aflatoxin B1 and B2a inhibited sialyltransferase(s) by 46% and 55%, respectively, while aflatoxin G1 inhibited sialyltransferase(s) by 54%. Aflatoxins B2 and G2 were only slightly inhibitory. It is proposed that the enzyme inhibition caused by these various aflatoxins is due to binding of these agents to the membranes resulting in a local disruption of the membrane and a change in enzyme conformation.

Aflatoxins↗

PubMedDate not supplied

Acute toxicity of aflatoxin B1 and rubratoxin B in dogs.

The effect of ip administrated aflatoxin B1 and rubratoxin B, singly and in combination, on dogs was determined by serum tests, by observations of clinical signs and survival times, and by evaluation of gross and microscopic lesions. The dog is sensitive to the toxic effects of both mycotoxins. Glutamic-oxaloacetic transaminase, lactic dehydrogenase and alkaline phosphatase activities and survival time varied in relation to dose and to the mycotoxin(s) administered. All three plasma enzymes were elevated regardless of dose with the combination of aflatoxin B1/rubratoxin B at 24 hr after dosing, except LDH, which was within the normal range but only at the lowest dose level. Several serum constituents including BUN, cholesterol, uric acid, and total bilirubin were elevated, whereas serum glucose was depressed in dogs treated with the multiple-toxin regimen; these changes were not seen in dogs given only aflatoxin B1 but were characteristic in rubratoxin-treated animals. In general, gross findings at necropsy were similar in all dogs regardless of the dose regimen. A striking similarity existed in the histologic changes observed between lesions experimentally induced by the mycotoxin combination and those lesions reported for dogs fed toxic feed in laboratory studies or in natural cases of hepatitis X. Of particular similarity were the severe kidney lesions observed in dogs exposed to the mycotoxin combination and kidney lesions reported in natural outbreaks of hepatitis X. There can be little doubt of an association between hepatitis X and aflatoxin B1, although it is apparent that the disease probably involves more than a single toxic factor. Our results suggest that hepatitis X in dogs includes aflatoxin B1 as a primary etiological factor but that rubratoxin B also may be involved.

Aflatoxins↗

PubMed1977

Dietary aflatoxins and human primary liver cancer.

The results of the dietary aflatoxin-liver cancer study carried out in the Murang'a district of Kenya have been reassessed in relation to disease incidence rates based on a total of seven years of cancer registration and related to the Population Census carried out during the course of the initial study. These newly derived data have been combined with the results of a second similar dietary aflatoxin-liver cancer study which was later carried out in Swaziland. Separate treatment of the male and female data has been considered necessary due to the variation of the sex ratio of the disease incidence in the two areas. The combined results of the two studies show a high degree of positive correlation between the calculated ingestion levels of aflatoxin, expressed as ng/kg bodyweight/day (x) and the adult incidence rates of hepatocellular carcinoma expressed as cases/10(5) adults/year (y) within the two study populations and this is true for both males and females. Based upon an assumed 2 kg/day intake of wet diet and a mean bodyweight of 70 kg, the calculated relationship for adult females is: y = 4.14 log10 x--0.80 (0.05 greater than P4 greater than 0.02, tor = +/- 2.90). With the added assumption of a daily intake of native beer of two liters/day the regression equation for adult males is: y = 21.96 log10 x--11.17 (P5 less than 0.001, tor = +/- 3.42). The regression data are found to be essentially compatible with comparable data recorded by independent workers in Thailand and Mozambique; the latter being the region where the highest rates of liver cancer and of aflatoxin ingestion levels have so far been recorded. A highly significant regression line has also been calculated using crude disease incidence data and aflatoxin exposure levels from all available studies: y = 7.60 log10 x--3.60 (P8 less than 0.001, tor = +/- 3.10).

Aflatoxins↗

PubMed1978

Complement activity, serum protein, and hepatic changes in guinea pigs given sterigmatocystin or aflatoxin, alone or in combination.

Effects of either sterigmatocystin or aflatoxin, alone or in combination, given orally to guinea pigs were studied. Sterigmatocystin and aflatoxin B1 given alone and in combination at 4.2 mg/day and 0.01 mg/day, respectively, markedly reduced body weight. Although changes in total serum protein were not marked in any of the guinea pigs in this study, sterigmatocystin given alone and aflatoxin given alone significantly ( less than 0.05) decreased alpha2-globulin. The combination of toxins significantly (P less than 0.01) increased albumin and significantly (P less than 0.01) decreased both alpha2- and beta-globulins. Sterigmatocystin depressed complement activity, although not significantly. However, the combination of sterimatocystin with 0.01 mg of aflatoxin B1/day (an amount that does not affect complement activity alone) significantly (P less than 0.01) reduced complement activity. Increased severity of lesions was not found in guinea pigs given aflatoxin at 0.01 mg of B1 equivalents/day in addition to the sterigmatocystin.

Aflatoxins↗

PubMed1978

Effects of aflatoxin on the development of acquired immunity to swine erysipelas.

The effect of aflatoxin consumption on the development of acquired immunity to swine erysipelas was studied. Twenty-four pigs were divided into 4 groups (6 pigs/group). Two groups were fed a normal diet and 2 groups were fed the same diet but containing aflatoxin. One group from each diet treatment was given a single injection of an erysipelas bacterin, and 21 days later all pigs were given a challenge inoculum of virulent Erysipelothrix rhusiopathiae organisms. On the basis of the response to the challenge inoculation, pigs were classified as immune, partially immune (PI), or susceptible. Three of the vaccinated pigs fed the normal diet were immune, 2 were PI, and 1 was susceptible, whereas none of the vaccinated pigs given the aflatoxin diet were immune, only 1 was PI, and the remainder were susceptible. Two of the nonvaccinated pigs fed the normal diet were PI and 4 were susceptible; all of the nonvaccinated pigs fed the aflatoxin diet were susceptible. It was concluded that aflatoxin consumption interfered with the development of acquired immunity and apparently increased the severity of the E rhusiopathiae infection in unvaccinated pigs.

Aflatoxins↗

PubMed1983

[Preparation and identification of aflatoxin B2a under laboratory conditions].

The method of preparing and identifying small quantities of aflatoxin B2a after Pohland et al. (1968) was verified as it was necessary to differentiate various types of aflatoxins in analytic practice. Aflatoxin B2a was prepared by the hydroxylation of aflatoxin B1 in acid medium and was identified by thin silica gel layer chromatography (TLC) and by spectral analysis in methanol medium and in a mixture of methanol with ammonium hydroxide (14 + 1). The results of both methods of identification were in keeping with the results of earlier works. At TLC in the system of chloroform + methanol (95 + 5) the Rf values were as follows: Rf AFB1--0.68 and Rf AFB2a--0.32; in the system of chloroform + acetone + isopropyl alcohol (85 + 10 + 5) the respective values were Rf AFB1--0.46 and Rf AFB2a--0.22. Spectral analysis demonstrated a shift in the absorption maximum in the methanol + ammonium hydroxide medium from 362 nm to 404 nm in aflatoxin B2a. The yield rate of AFB2a was about 50 to 55%.

Aflatoxins↗

PubMedDate not supplied

The toxic and teratogenic effect of aflatoxin B1 on the chick embryo development.

The embryotoxic and teratogenic effect of aflatoxin B1 was tested on the chick embryo. Aflatoxin B1 was injected into the embryonic area in doses of 1/100 ppm and 1/500 ppm in the 96th h of incubation. Aflatoxin B1 toxicity caused a rise in the mortality rate from 6.6% (controls) to 35% in the chicken injected with 1/100 ppm aflatoxin B1 and to 26% in the lot given 1/500 ppm. Several malformations were also noticed: spina bifida, anophthalmia, maxillary retrognathism, distorted legs and evisceration; the group receiving 1/100 ppm aflatoxin B1 also showed bone development retardation of the wing, leg, maxilla and mandible.

Abnormalities, Drug-Induced↗

PubMed1983

Rapid liquid chromatographic determination of aflatoxins in heavily contaminated corn.

A procedure is described for rapid, quantitative determination of aflatoxins B1, B2, G1, and G2 in heavily contaminated corn (greater than 500 micrograms B1/kg) from field, greenhouse, and growth chamber experiments employing artificial inoculation of corn with Aspergillus flavus. Whole kernel corn is ground to pass a 1 mm screen and mixed before extraction of a water-wetted (25 mL) 50 g subsample with 250 mL chloroform. The filtered extract is diluted 1:1 with hexane and applied to a hexane-wetted (10 mL) disposable silica cartridge. Interferences are removed with chloroform-hexane (1 + 3), and aflatoxins are quantitatively eluted with hexane-acetone (1 + 1). Aflatoxins B1 and G1 are converted to the more intensely fluorescent hemiacetals, B2a and G2a, by treatment with trifluoroacetic acid-water. Derivatized aflatoxins are separated by reverse phase liquid chromatography (LC) and quantitated fluorometrically. Compared with AOAC method I (CB) for corn, using samples containing approximately 50 and 10 000 micrograms B1/kg, agreement between methods was good at the lower level while the rapid method yielded a considerably larger mean at the higher level. A precision study of 30 replicate samples produced a coefficient of variation of 8.46% at a mean value of 1066 micrograms B1/kg. The cartridge method was developed for LC analysis of samples that contain greater than 500 micrograms aflatoxin B1/kg corn, but it may be used to quantitate as little as 10 micrograms B1/kg with no modification.

Aflatoxins↗

PubMed1980

Influence of gamma irradiation of aflatoxin B1 production by Aspergillus flavus growing on some Nigerian foodstuffs.

Spores of Aspergillus flavus (UI, 81) inoculated into some local food materials were irradiated at 62.5, 125.0, 250.0 and 500.0 krad, and the effect on aflatoxin B1 production on subsequent incubation was measured. The results show that aflatoxin B1 production decreased with increasing gamma irradiation dose in soya bean, groundnut, palm juice, while paw paw mash showed a relatively high yield of aflatoxin at 125.0 krad as compared to other irradiation levels tested except for the control. Irradiation of soya bean and groundnut inoculated with spores of Aspergillus flavus at 500.0 krad (pre-irradiation incubation period of 2 h) inhibited aflatoxin B1 production. Analysis of variance showed that media, pre-irradiation incubation periods and irradiation levels affected the total amounts of aflatoxin produced.

Aflatoxins↗

PubMed1978

High pressure liquid chromatographic determination of aflatoxins in peanut products.

A precise and sensitive high pressure liquid chromatographic method is proposed for determining aflatoxins B1, B2, G1, and G2 in all types of peanut products. The method is based on acidified aqueous methanol extraction, partition of aflatoxins into dichloromethane, and purification of the extract on a 2 g silica gel column. Aflatoxins in the purified extract are completely resolved on a microparticulate (10 micron) porous silica gel column in approximately 10 min with a water-saturated chloroform-cyclohexane-acetonitrile solvent. The preferred detection system, B1, and B2 by ultraviolet absorbance at 360-365 nm and G1 and G2 by fluorescence, allows accurate and sensitive detection of all 4 aflatoxins at levels as low as 0.3-1.0 microgram/kg. Repetitive assay of 3 samples of naturally contaminated peanut butters containing total aflatoxins (B1 + B2 + G1 + G2) at levels of 5, 10, and 15 microgram/kg gave within-laboratory coefficients of variation of 11, 5, and 5% respectively.

Aflatoxins↗