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PubMed1978

Some high-performance liquid-chromatographic studies of the metabolism of aflatoxins by rat liver microsomal preparations.

The metabolism of aflatoxin B1 in vitro was examined in rat liver microsomal preparations. 2. H.p.l.c. (high-performance liquid-chromatographic) systems were used. A silica column was used to separate non-polar metabolites. A system utilizing a reversed-phase column which separates both poar and non-polar metabolites was also developed. 3. The principal metabolites of aflatoxin B1 found were aflatoxin M1, aflatoxin Q1 and a compound which co-chromatographed with a degradation product of aflatoxin B1 2,3-dihydrodiol. 4. The time course of metabolism of aflatoxin B1 by microsomal preparations isolated from control and phenobarbitone-pretreated rats was examined. The rate and extent of metabolism was greater with microsomal preparations from the latter. The formation of aflatoxin Q1 was enhanced 4--5-fold by phenobarbitone pretreatment, whereas the production of aflatoxin M1 was only increased 1--2-fold. The formation of the degradation product of aflatoxin B1 2,3-dihydrodiol was increased 4--5-fold by the pretreatment with phenobarbitone. 5. The microsomal metabolism of aflatoxins M1, P1 and Q1 was examined. Aflatoxin M1 apparently underwent very limited microsomal metabolism to more polar compounds. Aflatoxin P1 was not metabolized. The situation with aflatoxin Q1 was complicated in that it was metabolized in the absence of NADPH to an unidentified metabolite. Aflatoxin B1 appeared as a metabolite of aflatoxin Q1 only when NADPH was present, and the formation of more polar metabolites was also then observed.

Aflatoxins↗

PubMed1997

Anti-aflatoxin mutagenic factors in corn.

Extracts, isolated through sequential fractionation and partition procedures described previously (Martinez et al. 1994) from aflatoxin-free corn and aflatoxin-contaminated corn with and without ammonia treatment, were investigated for mutagenic potential using the Ames test (TA 100 tester strain). 2-Aminofluorene (2-AF) and pure aflatoxin B1 (AFB1) were used as positive controls. Although TA100 showed mutagenic response to pure AFB1 at a dose of ca 10 ng/plate, all isolates tested from ammonia-treated aflatoxin-contaminated corn containing 7500 ng AFB1/g did not exhibit positive results in the Ames test. Additionally, isolates from non-ammonia-treated aflatoxin-contaminated corn failed to give positive mutagenic potentials. These results indicate that differences between the mutagenic potentials of pure aflatoxins and of aflatoxins in naturally-contaminated corn exist. CH2Cl2 extracts (the fractions containing aflatoxins) obtained from aflatoxin-contaminated corn with and without ammonia treatment were applied to preparative thin layer chromatography (TLC) in an effort to separate aflatoxins and/or ammonia/aflatoxin reaction products from the "unknown interfering materials' existing in the corn matrix. Each of the fractions separated by TLC was tested by the Ames test with S9 activation and none of them gave a mutagenic response to TA100. CH2Cl2 extracts in dimethylsulphoxide (DMSO) obtained from non-ammonia-treated aflatoxin-free corn were spiked with pure AFB1 and tested by TA100 with S9 activation. Again, no positive responses were observed. These findings provide further evidence of "unknown interfering materials' in corn which may bind with aflatoxin and/or can be extracted by CH2Cl2 together with aflatoxin, and, therefore, block the mutagenic activity of aflatoxin in the Ames test. Those materials were not separated from the aflatoxins by the TLC technique used in the present study. Possible reasons and further studies required to evaluate this phenomenon are discussed.

Aflatoxins↗

PubMed1983

Effect of dietary aflatoxin concentration on the assessment of genetic variability of response in a randombred population of chickens.

The effect of graded levels of dietary aflatoxin on the assessment of genetic variability of body weight and gain and plasma protein response was tested utilizing the Athens-Canadian randombred population of chickens. Dietary aflatoxin was administered at levels of either 0, 1.25, 2.50 or 5.0 microg/g of diet ad libitum from 7 to 21 days of age to progeny from 58 sire families. Twenty-one-day body weights, gain and plasma protein concentration were used to assess the variation in response.-The administration of increasing levels of aflatoxin resulted in a dose-related decrease of gains and plasma protein concentrations. Plasma protein concentrations were significantly higher among males than females within the control group; however, this difference was reversed as the severity of the aflatoxin challenge increased. Heritability estimates for all responses increased as the level of aflatoxin administered increased. This change was most notable for total plasma protein concentration. Phenotypic correlations for plasma protein concentration and growth measurements tended to diminish with increasing levels of aflatoxin. A similar trend was noted for the genetic correlations; however, a moderate correlation between growth responses and plasma protein response was detected in the 5.0-microg/g aflatoxin treatment group. Genetic correlations were calculated for the same characters between the different levels of aflatoxin. Regardless of which aflatoxin challenges were compared, a very high genetic correlation for 21-day body weight and 7- to 21-day gain was estimated. This variation in growth potential in the toxic environment paralleled that observed in the control environment but at a lower plane. Genetic correlations for plasma protein response across aflatoxin levels diminished as the difference between the levels of aflatoxin administered increased. Plasma protein concentration in the control environment was positively correlated with plasma protein response in groups fed a low level of aflatoxin, but negatively correlated when an aflatoxin challenge of 2.5 microg/g or more was given, suggesting that selection for aflatoxin resistance using plasma protein response as a selection criterion should be made under an aflatoxin stress environment.

Aflatoxins↗

PubMed1988

Substances with affinity to a monoclonal aflatoxin B1 antibody in Danish urine samples.

Using a competitive enzyme immunoassay, one or more substances recognized by a monoclonal antibody against aflatoxin B1 were detected in human urine samples collected in Denmark. The concentration of urinary aflatoxin-like substances was equivalent to 0.0-6.5 ng aflatoxin B1/mg creatinine. A truly competitive interaction in the immunoassay was found between aflatoxin-like substances and aflatoxin B1. Aflatoxin-like substances could be isolated in small quantities from urine by affinity chromatography. The quantity of urinary aflatoxin-like compounds in the samples collected showed a skewed normal distribution (80 individuals). In order to explain the seemingly high level of aflatoxin-like material in urine samples from people living in a cold temperate climate, the source of aflatoxin-like compounds was investigated. In a dietary restriction study, potential dietary factors leading to excretion of aflatoxin-like compounds were investigated. Our data indicate that the excretion of these compounds by healthy Danes depends mainly on the food ingested 24-48 hr before urine samples were collected. In particular, the excretion of aflatoxin-like substances was increased when diets include beer, dairy products or meat. A map of the epitope recognized by the antibody was constructed from the results of competition studies with several AFB1 analogues. The epitope map was used to draw chemical structures representing the minimal requirements for antibody recognition. An on-line search was conducted among the 98.2 x 10(6) structures in the Chemical Abstracts and Registry Databases (STN, Columbus, OH) and provided strong evidence that only aflatoxins or aflatoxin derivatives are recognized by the antibody. The possible chemical structures of the aflatoxin-like substances are discussed.

Aflatoxin B1↗

PubMed1978

Aflatoxin is degraded by mycelia from toxigenic and nontoxigenic strains of aspergilli grown on different substrates.

The ability of 9-day-old mycelia of Aspergillus parasiticus NRRL 2999 to degrade aflatoxin varied depending on the substrate used to grow the mold. Substrates which allowed substantial mycelial growth yielded mycelia which actively degraded aflatoxin. Substrates which allowed minimal growth of mycelia yielded mycelia with little ability to degrade aflatoxin. Biodegradation of aflatoxin was also strain-dependent. A. parasiticus NRRL 2999 and NRRL 3000 actively degraded aflatoxin, A. flavus NRRL 3353 was less active, and A. flavus NRRL 482 and A. parasiticus NRRL 3315 degraded minimal amounts of aflatoxins. Those aspergilli producing greatest amounts of aflatoxin also degraded aflatoxins most rapidly, whereas those strains which produced minimal amounts of aflatoxin generally degraded aflatoxins less effectively. Substrates which allowed maximum aflatoxin production also yielded mycelia which actively degraded aflatoxins, whereas media which allowed limited production of aflatoxin generally yielded mycelia with minimal ability to degrade the toxin. Although exceptions exist, generally as aflatoxin production increased so did the ability of mycelia to degrade the toxin.

Aflatoxins↗

PubMed1978

Aflatoxin at several initial concentrations is degraded by different amounts of mycelium of Aspergillus parasiticus.

Increasing amounts of a blendure of 9-day-old mycelia of Aspergillus parasiticus NRRL 2999 added to aflatoxin-salts reaction mixtures resulted in increased rates at which aflatoxin B1 and G1 were degraded. Similarly, increasing the amount(s) of aflatoxin B1 and/or G1 in the aflatoxin-salts reaction mixture resulted in increased rates of degradation of aflatoxins B1 and G1 by mycelia. This mycelial blendure degraded aflatoxin G1 approximately 1.6 times more rapidly than aflatoxin B1 when comparable amounts of the aflatoxins were initially present. When the same mycelial blendure was used to compared combined effects of size of inoculum and initial aflatoxin concentration on aflatoxin degradation, it appeared that increasing the amount of either inoculum or aflatoxin resulted in a comparable increase in degradation of aflatoxin B1 and G1. Hence, doubling the amount of inoculum or of aflatoxin resulted in approximately doubled rates at which aflatoxins B1 and G1 were degraded.

Aflatoxins↗

PubMed1975

Production of aflatoxin and its partition between the medium and the mycelium of Aspergillus parasiticus during incubation under various conditions.

Spores of an aflatoxigenic strain of Aspergillus parasiticus were inoculated into a glucose-salts medium which was incubated with and without shaking at 28 degrees C for 15 days. Without shaking, maximal production of total aflatoxin and aflatoxins B1, G1, and G2 occurred at 5 days, whereas the maximal amount of B2 appeared after 7 days. Initially approximately 5% of the total toxins appeared in the mycelium but this increased to more than 60% after 5 days. Shaking of cultures during incubation served to reduce production of total aflatoxin and of each of the individual toxins. The maximal amount of total aflatoxin and of toxins B1 and G1 appeared in shaken cultures after 5 days, whereas 8 and 11 days were needed to obtain maximal amounts of B2 and G2, respectively. The mycelium of shaken cultures initially retained approximately 50% of the total aflatoxin and this increased to about 80% as the incubation progressed. Very little aflatoxin was synthesized at 35 and 45 degrees C and production of total aflatoxin and of each individual toxin was less at 15 degrees C than at 25 or 28 degrees C. When the medium contained 0.5 to 50% glucose, maximal amounts of total aflatoxin and of aflatoxins B1, G1 and G2 appeared in the presence of 30% glucose; only 20% glucose was needed to obtain the greatest amount of B2. The mycelium retained approximately 50% of total aflatoxin when the medium contained 5 to 20%. Neither aflatoxin G1 nor G2 were detected when the medium contained 0.05% ammonium sulfate and only B1, B2, and G1 appeared in the medium with 0.1% of the salt. Maximal production of each individual aflatoxin and of total aflatoxin occured with 1% of ammonium sulfate in the medium. The proportion of total aflatoxin retained by the mycelium decreased from 83 to 37% as the amount of ammonium sulfate in the medium was increased from 0,05 to 10%.

Aflatoxins↗

PubMed2000

Inhibition of aflatoxin M1 production by bovine hepatocytes after intervention with oltipraz.

It is well known that cattle ingesting aflatoxin B1 contaminated feed commodities excrete aflatoxin M1 into their milk. As aflatoxin M1 originates from hepatic metabolism, measures to prevent aflatoxin M1 formation need to be directed to either the immobilization of aflatoxin B1 in the gastrointestinal tract or the modification of hepatic metabolism of aflatoxin B1. Here we studied the influence of oltipraz and a second dithiolthione, (1,2) dithiolo (4,3-c)-1,2-dithiole-3,6 dithione (DDD) on bovine hepatic aflatoxin B1 biotransformation. Oltipraz inhibited aflatoxin B1 metabolism as no aflatoxin M1 and no aflatoxin B1-dihydrodiol, the second metabolite found in bovine hepatocytes, was formed. DDD did not significantly inhibit aflatoxin B1 metabolism. It could be demonstrated that the inhibition of aflatoxin B1 metabolism was due to the inhibition of several cytochrome P450 enzyme activities by oltipraz. In contrast, DDD inhibited only ethoxyresorufin O-deethylation activity. These findings suggest a high efficacy of oltipraz in inhibiting aflatoxin M1 contamination of milk from dairy cows exposed to aflatoxin B1 contaminated feeds.

Aflatoxin M1↗

PubMed1986

Aflatoxin decomposition in various soils.

The persistence of aflatoxin in the soil environment could potentially result in a number of adverse environmental consequences. To determine the persistence of aflatoxin in soil, 14C-labeled aflatoxin B1, was added to silt loam, sandy loam, and silty clay loam soils and the subsequent release of 14CO2 was determined. After 120 days of incubation, 8.1% of the original aflatoxin added to the silt loam soil was released as CO2. Aflatoxin decomposition in the sandy loam soil proceeded more quickly than the other two soils for the first 20 days of incubation. After this time, the decomposition rate declined and by the end of the study, 4.9% of the aflatoxin was released as CO2. Aflatoxin decomposition proceeded most slowly in the silty clay loam soil. Only 1.4% of aflatoxin added to the soil was released as CO2 after 120 days incubation. To determine whether aflatoxin was bound to the silty clay loam soil, aflatoxin B1 was added to this soil and incubated for 20 days. The soil was periodically extracted and the aflatoxin species present were determined using thin layer chromatographic (TLC) procedures. After one day of incubation, the degradation products, aflatoxins B2 and G2, were observed. It was also found that much of the aflatoxin extracted from the soil was not mobile with the TLC solvent system used. This indicated that a conjugate may have formed and thus may be responsible for the lack of aflatoxin decomposition.

Aflatoxins↗

PubMed1994

Dietary hydrated sodium calcium aluminosilicate reduction of aflatoxin M1 residue in dairy goat milk and effects on milk production and components.

Lactating dairy goats were exposed to aflatoxin (100 and 200 ppb) and hydrated sodium calcium aluminosilicate at 1, 2, and 4% in two separate experiments. Naturally occurring low levels of aflatoxin M1 (.009 ppb) were found in the milk of the control diet, whereas there were no detectable levels of aflatoxin M1 in the milk of diets containing hydrated sodium calcium aluminosilicate in both experiments. In Exp. 1, no treatment-related differences in clinical behavior or significant difference in the feed intake, milk production, or milk component analyses were observed with 200 ppb of aflatoxin and 4% hydrated sodium calcium aluminosilicate. However, 4% hydrated sodium calcium aluminosilicate was responsible for an 86.9% reduction of aflatoxin M1 residue in the milk of diary goats. In Exp. 2, the combination of 1% hydrated sodium calcium aluminosilicate and aflatoxin at 100 ppb resulted in an overall reduction of aflatoxin M1 residue by 51.9%, which represented a mean change of aflatoxin M1 from .553 to .266 ppb of aflatoxin M1 in the milk. The diet that contained 2% hydrated sodium calcium aluminosilicate and 100 ppb of aflatoxin further reduced aflatoxin residue by a mean change from .553 to .098 of ppb aflatoxin M1, which represents an 82.2% reduction of aflatoxin M1 residue in the milk. Analysis of the data by time indicated that there were no statistical differences between days of sampling. Information regarding the ability of hydrated sodium calcium aluminosilicate to prevent or reduce the level of aflatoxin M1 residues in milk is critically needed.(ABSTRACT TRUNCATED AT 250 WORDS)

Aflatoxin M1↗

PubMed1997

Overexpression of aflR Leads to Upregulation of Pathway Gene Transcription and Increased Aflatoxin Production in Aspergillus flavus.

The aflatoxin biosynthetic pathway regulatory gene, aflR, encodes a putative 47-kDa protein containing a zinc cluster DNA binding motif. It is required for the transcription of all of the characterized aflatoxin pathway genes in both Aspergillus flavus and Aspergillus parasiticus. The objective of this study was to examine the effects of aflR overexpression on temporal gene expression, aflatoxin production, and nitrate inhibition of aflatoxin biosynthesis in A. flavus. An inducible expression construct was made by fusing the coding region of aflR to the promoter region of the A. flavus adh1 gene. This construct was transformed into A. flavus 656-2 (FGSC A1010), a strain mutated at the aflR locus. Strain 656-2 containing the adh1(p)::aflR construct had induced transcription of two early aflatoxin pathway genes, nor-1 and pksA, and produced wild-type concentrations of aflatoxin in a temporal pattern similar to that of wild-type strains of A. flavus. Strains 656-2 and 86-10 (FGSC A1009) an aflatoxigenic strain, were transformed with a construct containing the constitutive promoter gpdA driving aflR. Transformants of these strains constitutively expressed aflR, fas-1A, pksA, nor-1, and omtA but did not constitutively produce aflatoxin. Strain 86-10 containing the gpdA(p)::aflR construct produced 50 times more aflatoxin than 86-10, but the temporal pattern of aflatoxin production was the same as for 86-10, and aflatoxin production was also induced by sucrose. The addition of 10 g of nitrate per liter to sucrose low salts medium inhibited aflatoxin production by both strain 86-10 and a transformant of 86-10 containing the gpdA(p)::aflR construct, indicating that nitrate inhibition of aflatoxin biosynthesis does not occur solely at the level of aflR transcription. These studies show that constitutive overexpression of the pathway transcriptional regulatory gene aflR leads to higher transcript accumulation of pathway genes and increased aflatoxin production but that the initiation of aflatoxin biosynthesis is not solely regulated by the transcriptional activities of the biosynthetic pathway.

Journal Article↗

PubMed1983

Metabolite distribution and rate of residue clearance in turkeys fed a diet containing aflatoxin B1.

The retention of aflatoxin residues in tissues of turkey poults fed a diet containing aflatoxin B1 (500 ppb) for 18 days was determined. Free and conjugated aflatoxin metabolites were quantified using high-pressure liquid chromatography. Aflatoxin residue levels were greater in liver than muscle tissues, although all levels were low (range 0.01-1.19 ng/g tissue). Free and conjugated aflatoxins B1 and M1, a metabolite of B1, were the principal tissue residues. Other metabolites investigated included aflatoxicol, which was detected in certain samples, and aflatoxin Q1 which was not detected. Conjugated aflatoxins, hydrolysed and extracted from the aqueous tissue fractions, comprised 55-91% of the total detected aflatoxin residues. All aflatoxin residues were rapidly cleared following discontinuation of the dietary aflatoxin B1 (half-life 1.4 days for total aflatoxin clearance from liver). These results provide further evidence that tissues from animals maintained on diets containing aflatoxins do not provide a major source of aflatoxins when consumed by man.

Aflatoxin B1↗

PubMed1990

Intercalation of aflatoxin B1 in two oligodeoxynucleotide adducts: comparative 1H NMR analysis of d(ATCAFBGAT).d(ATCGAT) and d(ATAFBGCAT)2.

8,9-Dihydro-8-(N7-guanyl-[d(ATCGAT)])-9-hydroxyaflatoxin B1.d(ATCGAT) and 8,9-dihydro-8-(N7-guanyl-[d(ATGCAT)])-9-hydroxyaflatoxin B1.8,9-dihydro-8-(N7-guanyl-[d(ATGCAT)])-9-hydroxyaflatoxin B1 were prepared by direct addition of afltoxin B1 8,9-epoxide to d(ATCGAT)2 and d(ATGCAT)2, respectively. In contrast to reaction of aflatoxin B1 8,9-epoxide with d(ATCGAT)2 which exhibits a limiting stoichiometry of 1:1 aflatoxin B1:d(ATCGAT)2 [Gopalakrishnan, S., Stone, M. P., & Harris, T. M. (1989) J. Am. Chem. Soc. 111, 7232-7239], reaction of aflatoxin B1 8,9-epoxide with d(ATGCAT)2 exhibits a limiting stoichiometry of 2:1 aflatoxin B1:d(ATGCAT)2. 1H NOE experiments, nonselective 1H T1 relaxation measurements, and 1H chemical shift perturbations demonstrate that in both modified oligodeoxynucleotides the aflatoxin moiety is intercalated above the 5'-face of the modified guanine. The oligodeoxynucleotides remain right-handed, and perturbation of the B-DNA structure is localized adjacent to the adducted guanine. Aflatoxin-oligodeoxynucleotide 1H NOEs are observed between aflatoxin and the 5'-neighbor base pair and include both the major groove and the minor groove. The aflatoxin methoxy and cyclopentenone ring protons face into the minor groove; the furofuran ring protons face into the major groove. No NOE is observed between the imino proton of the modified base pair and the imino proton of the 5'-neighbor base pair; sequential NOEs between nucleotide base and deoxyribose protons are interrupted in both oligodeoxynucleotide strands on the 5'-side of the modified guanine. The protons at C8 and C9 of the aflatoxin terminal furan ring exhibit slower spin-lattice relaxation as compared to other oligodeoxynucleotide protons, which supports the conclusion that they face into the major groove. Increased shielding is observed for aflatoxin protons; chemical shift perturbations of the oligodeoxynucleotide protons are confined to the immediate vicinity of the adducted base pair. The imidazole proton of the modified guanine exchanges with water and is observed at 9.75 ppm. The difference in reaction stoichiometry is consistent with an intercalated transition-state complex between aflatoxin B1 8,9-epoxide and B-DNA. Insertion of aflatoxin B1-8,9 epoxide above the 5'-face of guanine in d(ATCGAT)2 would prevent the binding of a second molecule of aflatoxin B1 8,9-epoxide. In contrast, two intercalation sites would be available with d(ATGCAT)2.(ABSTRACT TRUNCATED AT 400 WORDS)

Aflatoxin B1↗

PubMedDate not supplied

Solvent-efficient thin-layer chromatographic method for the determination of aflatoxins B1, B2, G1, and G2 in corn and peanut products: collaborative study.

An interlaboratory study of a solvent-efficient thin-layer chromatographic (TLC) method for the determination of aflatoxins B1, B2, G1, and G2 was conducted in laboratories located in the United States, France, Tunisia, and Denmark. Eighteen artificially contaminated samples plus blanks of raw peanuts and peanut butter and corn containing varying amounts of aflatoxins B1, B2, G1, and G2 were distributed to participating laboratories. The method consists of elements of the U.S. Food and Drug Administration (FDA), Contaminants Branch (CB) (AOAC Method 968.22) and FDA, Best Foods (BF) (AOAC Method 970.45) methods with reduced requirements for solvents. Participating laboratories used either visual or densitometric techniques during the final determinative step. Statistical analysis of the data was performed to determine or confirm outliers and to compute repeatability and reproducibility of the method using either visual or densitometric techniques for the determinative step. Reported results from laboratories using a densitometer showed that, for corn, the relative standard deviation for repeatability (RSDr) for aflatoxin B1 ranged from 56.6 to 41.7% for contamination levels ranging from 5 to 50 ng/g. For raw peanuts and peanut butter, the RSDr values for aflatoxin B1 ranged from 21.3 to 37.3% and 65.9 to 42.1%, respectively, for the contamination levels ranging from 5 to 25 ng/g. RSDr ranges for aflatoxins B2, G1, and G2 were similar. For reproducibility (R), the RSDR ranges for aflatoxin B1 were 41.7-56.6%, 56.6-84.8%, and 26.4-37.3% for corn, peanut butter, and raw peanuts, respectively. Average recoveries for all aflatoxins at all levels were 95.3, 139.0, and 95.6% for corn, peanut butter, and raw peanuts, respectively. When analysts determined aflatoxin concentrations in corn by visual comparison to standards, the RSDr values for aflatoxin B1 were 47.8-11.4% for contamination levels ranging from 5 to 50 ng/g. For raw peanuts and peanut butter, the RSDr values for aflatoxin B1 were 76.3-12.6% and 33.4-8.8%, respectively, for the contamination levels ranging from 5 to 25 ng/g. RSDr values for aflatoxins B2, G1, and G2 were similar. The RSDR values for aflatoxin B1 were 34.6-90.2%, 45.5-59.3%, and 31.8-78.3% for corn, peanut butter, and raw peanuts, respectively. Average recoveries for all aflatoxins at all levels were 111.0, 157.6, and 92.3% for corn, peanut butter, and raw peanuts, respectively.(ABSTRACT TRUNCATED AT 400 WORDS)

Aflatoxin B1↗

PubMed1992

Aflatoxins in animal and human health.

Aflatoxins remain as a threat to the health of livestock as well as humans by their continuing intermittent occurrence in both feeds and foods. The finding that aflatoxin-contaminated feeds, and eventually purified aflatoxins, were carcinogenic in rats and trout initiated a multitude of studies in search of the role of these toxins in human liver disease, especially cancer. Although aflatoxins have caused acute liver disease in humans, epidemiologic evidence of the involvement of aflatoxins in PLC has not been clarified. Earlier studies did not consider that the hepatitis B virus (HBV) may have contributed to the PLC in the selected populations. Although later studies that did include measurement of the HBV antigen in serum provided conflicting evidence for the role of aflatoxin in PLC in these populations, the latest and most comprehensive study found no association between aflatoxin exposure and PLC mortality. The technological advances and findings of the chemical, immunologic, and metabolic activities of aflatoxins such as binding to DNA and protein to form adducts, development of monoclonal antibodies, and mutational specificity of the genotoxic compounds will, it is hoped, help to clarify the role of aflatoxin as a risk factor, among many others, in the development of primary liver cancer in humans. Aflatoxicosis of animals is usually manifested by pathologic changes in the liver, but they have been found to be carcinogenic and teratogenic as well as causing impaired protein formation, coagulation, weight gains, and immunity. The importance of the carcinogenic effect in livestock is diminished because they are not fed contaminated diets for a sufficient time prior to marketing for slaughter. Animals are variably susceptible to aflatoxins, depending on such factors as age, species, breed, sex, nutrition, and certain stresses. Swine, cattle, and poultry are the domestic species of greatest economic concern in terms of aflatoxicosis. In all species, the evidence of disease is a general unthriftiness and reduction in weight gains, feed efficiency, immunity, and production. More conclusive evidence of aflatoxin involvement in disease includes acute to chronic liver disease with concomitant increases in specific liver enzymes in the serum. In cattle, milk production is affected, but of greater significance is that the aflatoxins in feeds can be rather efficiently converted to toxic metabolites in milk, with even small amounts being readily detectable. The poultry industry probably suffers greater economic loss than any of the livestock industries because of the greater susceptibility of their species to aflatoxins than other species.(ABSTRACT TRUNCATED AT 400 WORDS)

Aflatoxins↗

PubMed2002

Effect of processing on aflatoxin.

Naturally occurring toxicant contamination of foods with mycotoxins is unavoidable and unpredictable and poses a unique challenge to food safety. Aflatoxins are toxic mold metabolites produced by toxigenic strains of Aspergillus species. Primary commodities susceptible to aflatoxin contamination include corn, peanuts and cottonseed and animal-derived foods such as milk when the animal is fed aflatoxin-contaminated feed. Risks associated with aflatoxin-contaminated foods can be reduced through the use of specific processing and decontamination procedures. Factors, which influence the effectiveness of a specific process or procedure, include the chemical stability of the mycotoxin(s), nature of the process, type and interaction with the food/feed matrix and interaction with multiple mycotoxins if present. Practical decontamination procedures must: 1) inactivate, destroy, or remove the toxin, 2) not produce or leave toxic residues in the food/feed, 3) retain the nutritive value of the food/feed, 4) not alter the acceptability or the technological properties of the product, and, if possible, 5) destroy fungal spores. For aflatoxins, multiple processing and/or decontamination schemes have been successful in reducing aflatoxin concentrations to acceptable levels. Physical cleaning and separation procedures, where the mold-damaged kernel/seed/nut is removed from the intact commodity, can result in 40-80% reduction in aflatoxins levels. Processes such as dry and wet milling result in the distribution of aflatoxin residues into less utilized fractions of the commodity. The ammoniation of aflatoxin-contaminated commodities has altered the concentrations as well as toxic and carcinogenic effects of aflatoxin by greater than 99%. Nonbiological materials such as selected anticaking agents covalently bind aflatoxins from aqueous suspensions, diminish aflatoxin uptake by animals, prevent acute aflatoxicosis, and decrease aflatoxin residues in milk. Ultimately, the best processing or decontamination process is one that is approved by regulatory agencies, cost-effective, and reduces the mycotoxin concentration to acceptable levels.

Aflatoxins↗

PubMed1972

The effect of aflatoxin B 1 on normal and cortisol-stimulated rat liver ribonucleic acid synthesis.

1. Aflatoxin B(1), administered in vivo, inhibits the incorporation of [(14)C]orotic acid in vivo into rat liver nuclei, and also inhibits both Mg(2+)- and Mn(2+)-dependent RNA polymerase activities in nuclei assayed in vitro. 2. Aflatoxin B(1) inhibits the cortisol-induced increase in incorporation of [(14)C]leucine in vivo, but does not affect the control value of this activity. 3. Aflatoxin B(1) administered in vivo inhibits the increase in nuclear Mg(2+)-dependent RNA polymerase activity, assayed in vitro, which results from the treatment with cortisol. 4. Adrenalectomy causes a decrease in Mg(2+)-dependent RNA polymerase activity. The effect on this enzymic activity of adrenalectomy plus treatment with aflatoxin B(1) is no greater than that of treatment with aflatoxin B(1) alone. 5. These results suggest that the inhibition of cortisol-stimulated biochemical pathways by aflatoxin B(1) is due to an inhibition of cortisol-stimulated RNA synthesis. 6. The cytoplasmic action of aflatoxin is thought to be due to a competition for receptor sites on the endoplasmic reticulum between steroid hormones and aflatoxin B(1). No evidence was obtained for a similar competition for nuclear receptor sites between [(3)H]cortisol and aflatoxin B(1). 7. No differences were observed between the activities of RNA polymerase preparations solubilized from control or aflatoxin-inhibited nuclei. 8. No differences in ;melting' profiles were observed between DNA and chromatin preparations isolated from control nuclei or from aflatoxin-inhibited nuclei. 9. It is suggested that aflatoxin B(1) exerts its effect on RNA polymerase by decreasing the template capacity of the chromatin and that the aflatoxin ;target' area of the chromatin includes that region which is stimulated by cortisol. This process, however, does not involve inhibiting the movement of cortisol from the outside of the hepatic cell to the nuclear chromatin.

Adrenalectomy↗

PubMed2006

Aflatoxin B1-induced DNA damage in Labeo rohita: protective effect of an antioxidant supplement, Amrita Bindu.

The present study was undertaken to investigate the effect of potent hepatocarcinogen aflatoxin B1 in adduct formation and DNA damage in Labeo rohita. Also, the salubrious efficacy of an antioxidant supplement Amrita Bindu (based on Indian system of Medicine) was investigated. Fish weighing 175-250 g were administered intraperitoneally a single dose of 100 microg aflatoxin B1/100 g body wt. and another group was given 20% solution of Amrita Bindu along with aflatoxin B1 at 100 microg/100 g body wt. On the 3rd and 6th day, the liver tissue was analyzed for aflatoxin concentration, aflatoxin-DNA adduct formation and DNA damage measured in terms of single strand breaks. The fishes administered with aflatoxin B1 showed elevated concentration of aflatoxin along with a parallel increase in the DNA adduct when compared with the controls. While the fish co-administered with Amrita Bindu showed 34% and 24% reduction in aflatoxin deposition (accumulation) and aflatoxin-DNA adduct formation respectively on the 3rd day, a further reduction by around 41% and 33% in aflatoxin deposition and DNA adduct formation respectively was observed on the 6th day. Furthermore, the increased single strand breaks (measured by alkaline single cell gel assay) and fragmentation observed in agarose gel electrophoresis in aflatoxin B1 administered fish were significantly reduced by Amrita Bindu co-administration. In conclusion, this is the first report to show aflatoxin B1-induced DNA adduct formation and DNA damage in one of the major Indian culturable fish, Labeo rohita. Also, our observations show that the antioxidant supplement, Amrita Bindu, has a potential role in ameliorating the aflatoxin B1-induced DNA damage thus suggesting its applicability in preventing the vital macromolecule DNA.

Aflatoxin B1↗