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PubMed2000

Blasticidin A derivatives with highly specific inhibitory activity toward aflatoxin production in Aspergillus parasiticus.

Blasticidin A (1), an antibiotic, has strong inhibitory activity toward aflatoxin production by Aspergillus parasiticus. We prepared some derivatives of 1 and examined their biological activities. Among them, derivatives 3 and 4 without the tetramic acid moiety of 1 maintained inhibitory activity toward aflatoxin production, but did not show antifungal activity or toxicity. RT-PCR experiments indicated that derivatives 3 and 4 as well as 1 significantly reduced the expression of genes encoding aflatoxin biosynthetic enzymes (pksA, ver-1 and omtA) and a regulatory gene (aflR) in A. parasiticus. These results suggested that derivatives 3 and 4 can inhibit aflatoxin production more specifically than 1 by inhibiting an early step prior to the expression of aflR in the pathway of aflatoxin biosynthesis.

Aflatoxins↗

PubMed1976

Effect of sex difference on the in vitro and in vivo metabolism of aflatoxin B1 by the rat.

Hepatic microsome-catalyzed metabolism of aflatoxin B1 (AFB1) to aflatoxin M1 and aflatoxin Q1 and the "metabolic activation" of AFB1 to DNA-alylating metabolite(s) were studied in normal male and female Sprague-Dawley rats, in gonadectomized animals, and in castrated males and normal females treated with testosterone. Microsomes from male animals formed 2 to 5 times more aflatoxin M1, aflatoxin Q1, and DNA-alkylating metabolite(s) than those from females. Castration reduced the metabolism of AFB1 by the microsomes from males by about 50%, whereas ovariectomy had no significant effect on AFB1 metabolism by the microsomes from females. Testosterone treatment (4 mg/rat, 3 times/week for about 6 weeks) of castrated immature males and immature females enhanced the metabolism of AFB1 by their microsomes. A sex difference in the metabolism of AFB1 by liver microsomes was also seen in other strains of rats tested: Wistar, Long-Evans, and Fischer. The activity of kidney microsomes for metabolic activation was 1 to 4% that of the liver activity and was generally lower in microsomes from male rats as compared to those from female rats of Sprague-Dawley, Wistar, and Long-Evans strains. The in vitro results obtained with hepatic microsomes correlated well with the in vivo metabolism of AFB1, in that more AFB1 became bound in vivo to hepatic DNA isolated from male rats and from a female rat treated with testosterone than that isolated from control female rats. These data suggest that the differences in hepatic AFB1 metabolism may be the underlying cause of the sex difference in toxicity and carcinogenicity of AFB1 observed in rats.

Aflatoxins↗

PubMed1999

[The review of the European Union documents relating to contamination of aflatoxins in food].

In the following review, Polish and European Union legislation, concerning maximum level of aflatoxins in foodstuffs, was reported. In this moment, no specific requirements exist but according to Food and Nutrition Law all kind of food ought to be free from aflatoxins. Practically, maximum aflatoxins level should be below the detection limit of official analytical method (thin layer chromatography)--5 micrograms/kg and 0.05 microgram/l for milk. Commission Directive 98/53/EC laying down the sampling methods and the methods of analysis for aflatoxins in foodstuffs and Commission Regulation No 152/98 setting maximum levels for aflatoxins in foodstuffs were presented. Also, Ministry of Health Draft Regulation, concerning maximum levels of contamination in food is prepared in accordance with EU regulation, was reported.

Aflatoxins↗

PubMed1979

[Determination of aflatoxins in cheeses].

To investigate cheeses for the presence of aflatoxins we chose the very sensitive method of Tuinstra and Bronsgeest (1975) used for the determination of aflatoxin M1 in milk. The method was slightly modified and the presence of aflatoxins was determined in 54 samples of different cheeses. Aflatoxin M1 was found out in 24% of the investigated samples. Most of positive samples were found among the soft cheeses (53.8 3/4), then in processed cheeses (13.6%) and in hard cheeses (12.5%). Aflatoxin M1 was not found in the group of mouldy cheeses and Olomouc cake cheeses, which were investigated in a smaller range. Positive findings did not exceed concentrations of 10 ng per kg, i.e. they did not even reach the value of permissible concentration as proposed in the Czech Socialist Republic for foods (5 microgram per kg).

Aflatoxins↗

PubMedDate not supplied

Determination of aflatoxin B1 in baby food (infant formula) by immunoaffinity column cleanup liquid chromatography with postcolumn bromination: collaborative study.

A collaborative study was conducted to evaluate the effectiveness of an immunoaffinity column cleanup liquid chromatography (LC) method for determination of aflatoxin B, in a milk powder based infant formula at a possible future European regulatory limit (0.1 ng/g). The test portion was extracted with methanol-water (8 + 2 [v + v]), filtered, diluted with water, and applied to an immunoaffinity column. The column was washed with water to remove interfering compounds, and the purified aflatoxin B1 was eluted with methanol. The separation and determination of the aflatoxin B1 was performed by reversed-phase LC and detected by fluorescence after postcolumn derivatization (PCD) involving bromination. PCD was achieved with either pyridinum hydrobromide perbromide (PBPB) or an electrochemical (Kobra) cell by addition of bromide to the mobile phase. The baby food (infant formula) test samples, both spiked and naturally contaminated with aflatoxin B1, were sent to 14 laboratories in 13 different European countries. Test portions were spiked at levels of 0.1 and 0.2 ng/g for aflatoxin B1. Recoveries ranged from 101 to 92%. Based on results for spiked test samples (blind pairs at 2 levels) and naturally contaminated test samples (blind pairs at 3 levels), the relative standard deviation for repeatability (RSDr) ranged from 3.5 to 14%. The relative standard deviation for reproducibility (RSDR) ranged from 9 to 23%. Nine participants used PBPB derivatization, and

Aflatoxin B1↗

PubMed2001

Vitamin E ameliorates aflatoxin-induced biochemical changes in the testis of mice.

AIM: To assess the effect of aflatoxin on biochemical changes in the testis of mice and the possibility of amelioration by vitamin E treatment. METHODS: Adult male albino mice were orally administered with 25 or 50 microg of aflatoxin/animal/day (750 or 1500 microg/kg body weight) for 45 days. The testis was isolated and processed for biochemical analysis. RESULTS: There was a significant, dose-dependent reduction in DNA, RNA, protein, sialic acid contents and the activities of succinic dehydrogenase, adenosine triphosphatase and alkaline phosphatase in the testis of aflatoxin-treated mice as compared to the vehicle control. However, the acid phosphatase activity was significantly increased in the aflatoxin-treated mice. Vitamin E (2 mg/animal/day) treatment significantly ameliorated the aflatoxin-induced changes, except the acid and alkaline phosphatase activities in the high dose group. CONCLUSION: Vitamin E treatment ameliorates the aflatoxin-induced changes in the testis of mice.

Acid Phosphatase↗

PubMedDate not supplied

Interaction of aflatoxin with Eimeria tenella infection and monensin in young broiler chickens.

Young broiler chicks inoculated with Eimeria tenella and given a diet containing 2.5 mug aflatoxin/g had significantly higher mortality than birds with aflatoxicosis or coccidiosis alone or uninoculated controls. This effect was seen even when a light coccidial infection alone did not increase mortality or cause weight depression. In addition this higher mortality with the combination began earleir and occurred at a higher rate than did mortality from aflatoxin or cecal coccidiosis alone. Dietary monensin sodium (99 umg/g) did not completely prevent mortality and weight depression when aflatoxin and E. tenella were in combination. Aflatoxin and E. tenella singly significantly depressed three-week body weights; however, the depression was most severe when the two were in combination. Both dietary aflatoxin and E. tenella significantly reduced hemoglobin, packed cell volume, and plasma pigmentation, and in combination resulted in more severely reduced hemoglobin, packed cell volume, and plasma pigmentation. Coccidial lesion scores were significantly less for the combination of E. tenella and aflatoxicosis than for coccidiosis alone. This atypical response of the ceca to E. tenella in the presence of dietary aflatoxin was characterized by less distended ceca, very little coagulated blood in the ceca, and apparently more profuse cecal hemorrhage.

Aflatoxins↗

PubMedDate not supplied

Cleanup procedure for determination of aflatoxins in major agricultural commodities by liquid chromatography.

A simple, fast, reliable, and inexpensive chemical cleanup procedure was developed for quantitation of aflatoxins in major important agricultural commodities by liquid chromatography (LC). Aflatoxins were extracted from a ground sample with methanol-water (80 + 20, v/v), and after a single cleanup step on a minicolumn packed with basic aluminum oxide, they were quantitated by LC equipped with a C18 column, photochemical reactor, and fluorescence detector. Water-methanol-1-butanol (1,400 + 720 + 25, v/v/v) served as the mobile phase. Recoveries of aflatoxins B1, B2, G1, and G2 from peanuts spiked at 5.0, 2.5, 7.5, and 2.5 microg/kg were 87.2 +/- 2.3, 82.0 +/- 0.8, 80.0 +/- 1.8, and 80.4 +/- 2.8%, respectively. Similar recoveries, precision, and accuracy were achieved for corn, cottonseed, almonds, Brazil nuts, pistachios, and walnuts. The quantitation limit for aflatoxin B1 was 1 microg/kg. The minimal cost of the minicolumn allows for substantial savings compared with available commercial aflatoxin cleanup devices.

Aflatoxins↗

PubMedDate not supplied

Interaction of the aflatoxins with classical antibiotics which inhibit Bacillus brevis (2611).

Synergism, antagonism and addictive action are three modes of interaction among antibiotics and non-antibiotic compounds. The present paper reports the type of interaction between each of the four main members of the aflatoxin family (BB, G and G) and each of five commonly used classical antibiotics. The test aflatoxins were freshly prepared and confirmed crystalline pure by the use of ultraviolet (u.v.), infrared (i.r.) and nuclear magnetic resonane (n.m.r.) spectroscopy. Interaction between penicillin and aflatoxin B (AFB) gave an antagonistic profile. The interaction of AFB with tetracycline was synergistic. Novobiocin interaction with aflatoxin G also reflected synergism. All other characteristics of interaction between antibiotics and the aflatoxins showed additive profiles.

Aflatoxins↗

PubMed1976

An aflatoxin in the liver of a patient with Reye-Johnson syndrome.

Liver specimens from 8 patients with Reye-Johnson syndrome, 2 patients with acute encephalopathy, and 10 patients without liver disease were analyzed for aflatoxins. An aflatoxin was obtained from the liver of one patient, a 15-year-old girl who had clinical, laboratory, and pathologic features of Reye-Johnson syndrome. Thin-layer chromatography, fluorescence emission, infrared spectroscopy, and derivatization studies characterized the aflatoxin as related structurally to but not identical with aflatoxin B1. This report is added to previous ones from Thailand, New Zealand, and Czechoslovakia in which the association of aflatoxins and fatty liver has been found in Reye-Johnson syndrome.

Adolescent↗

PubMedDate not supplied

[Products of spontaneous conjugation of aflatoxins with bovine serum albumin: immunochemical properties].

Products of spontaneous conjugation of aflatoxins B1, G1, and G2 with bovine serum albumin (BSA) were shown to interact with antibodies against aflatoxins. Solid-phase BSA conjugates inhibited the binding of aflatoxins by anti-aflatoxin antibodies. Antisera against BSA-B1, BSA-G1, and BSA-G2 were obtained and their specificity, determined. The mechanisms of spontaneous binding of aflatoxins by proteins are discussed.

Aflatoxins↗

PubMed1992

Low frequency of p53 gene mutation in tumors induced by aflatoxin B1 in nonhuman primates.

Aflatoxin B1 has been suggested as a causative agent for a G to T mutation at codon 249 in the p53 gene in human hepatocellular carcinomas from southern Africa and Qidong in China. To test this hypothesis, nine tumors induced by aflatoxin B1 in nonhuman primates were analyzed for mutations in the p53 gene. These included four hepatocellular carcinomas, two cholangiocarcinomas, a spindle cell carcinoma of the bile duct, a hemangioendothelial sarcoma of the liver, and an osteogenic sarcoma of the tibia. None of the tumors showed changes at the third position of codon 249 by cleavage analysis of the HaeIII enzyme site at codon 249. A point mutation was identified in one hepatocellular carcinoma at the second position of codon 175 (G to T transversion) by sequencing analysis of the four conserved domains (II to V) in the p53 gene. These data suggest that mutations in the p53 gene are not necessary in aflatoxin B1 induced hepatocarcinogenesis in nonhuman primates. The occurrence of mutation in codon 249 of the p53 gene in selective samples of human hepatocellular cancers may indicate involvement of environmental carcinogens other than aflatoxin B1 or that hepatitis B virus-related hepatitis is a prerequisite for aflatoxin B1 induction of G to T transversion in codon 249.

Adenoma, Bile Duct↗

PubMed2003

Effect of gamma irradiation on elimination of aflatoxins produced by apple mycoflora in apple fruits.

The influence of ionizing radiation on the growth of apple mycoflora and the aflatoxins production was investigated. Four strains of fungal isolates, Aspergillus flavus, A. fumigatuis, A. niger, Penicillium expansum, were used. Four doses of gamma radiation were applied (0.5, 1.0, 1.5 and 2.0 KGy). The elimination of aflatoxins under selected conditions was detected by using HPLC techniques. Doses of 0.5 KGy stimulated the production of aflatoxins by all fungi tested while 1.0-2.0 KGy reduced the aflatoxins production. The studies were also carried out to investigate the effect of pre- and post-inoculation of both irradiated and non-irradiated fungal spores on irradiated and non-irradiated apples. The results showed the necessity of irradiation of fresh apple fruits followed by good preservation conditions. The results showed also that the effect of radiation is influences on the apple mycoflora producing aflatoxins and not the apple itself.

Aflatoxins↗

PubMed2005

Aflatoxin contamination of developing corn kernels.

Preharvest of corn and its contamination with aflatoxin is a serious problem. Some environmental and cultural factors responsible for infection and subsequent aflatoxin production were investigated in this study. Stage of growth and location of kernels on corn ears were found to be one of the important factors in the process of kernel infection with A. flavus & A. parasiticus. The results showed positive correlation between the stage of growth and kernel infection. Treatment of corn with aflatoxin reduced germination, protein and total nitrogen contents. Total and reducing soluble sugar was increase in corn kernels as response to infection. Sucrose and protein content were reduced in case of both pathogens. Shoot system length, seeding fresh weigh and seedling dry weigh was also affected. Both pathogens induced reduction of starch content. Healthy corn seedlings treated with aflatoxin solution were badly affected. Their leaves became yellow then, turned brown with further incubation. Moreover, their total chlorophyll and protein contents showed pronounced decrease. On the other hand, total phenolic compounds were increased. Histopathological studies indicated that A. flavus & A. parasiticus could colonize corn silks and invade developing kernels. Germination of A. flavus spores was occurred and hyphae spread rapidly across the silk, producing extensive growth and lateral branching. Conidiophores and conidia had formed in and on the corn silk. Temperature and relative humidity greatly influenced the growth of A. flavus & A. parasiticus and aflatoxin production.

Aflatoxins↗

PubMed1976

Induction of liver tumors by aflatoxin B1 in the tree shrew (Tupaia glis), a nonhuman primate.

The epidemiological studies suggest that aflatoxins, the toxic metabolites of the ubiquitous mold Aspergillus flavus, may play a significant role in the evolution of hepatocellular carcinoma in man in certain geographic areas of the world. To ascertain their carcinogenicity in nonhuman primates, we have administered highly purified aflatoxin B1, intermittently in the diet at 2 ppm, to 10 female and 8 male tree shrews. The tree shrew (Tupaia glis) is a nonhuman primate occurring throughout Southeast Asia which can be reared easily in captivity. Of 12 animals that survived, 6 of 6 female (100%) and 3 of 6 male (50%) tree shrews developed hepatocellular carcinomas between 74 and 172 weeks after the beginning of the experiment. None of the 8 control animals developed liver cancers. The estimated total amount of aflatoxin B1 consumed by these animals ranged from 24 to 66 mg. The development of liver tumors did not follow a specific pattern; considerable variation in hepatocellular responses to aflatoxin B1 was noted in these animals. In 2 tree shrews, the liver tumors were associated with severe post necrotic scarring; in the other 7 tumor-bearing livers, only mild to moderate portal fibrosis was encountered. This individual variation in hepatocellular response and in the amount of aflatoxin B1 required to induce hepatocellular carcinomas is attributed to inherent differences in the susceptibility within a given species of outbred animals and suggests extreme caution in proposing the "permissible" or "safe" levels of contamination of carcinogens in the food-stuffs.

Aflatoxins↗

PubMed1991

Possible effect of infection with liver fluke (Opisthorchis viverrini) on the monitoring of urine by enzyme-linked immunosorbent assay for human exposure to aflatoxins.

Several laboratories have initiated studies to assess human exposure to aflatoxin at an individual level by measuring aflatoxin metabolites in the urine by immunoassay. The fact that the antibodies recognize a variety of metabolites, albeit with differing affinities, means that any environmental factor that modifies the pattern of urinary metabolites associated with a given exposure could affect quantification in immunoassay. We have examined two such possible effects: (i) the pattern of metabolites after a dose of 14C-aflatoxin B1 in rats and (ii) the pattern of metabolites in hamsters and humans with and without exposure to liver flukes. We found no dose-related effect on the pattern of urinary metabolites over a 250-fold range, but there was a significant increase in the proportion of water-soluble aflatoxin metabolites in hamsters infected with liver fluke over that in uninfected animals. In human urine samples, there also appeared to be a difference in the metabolites in individuals infected with liver fluke from those in uninfected persons. These observations are relevant to both mechanistic and monitoring aspects of research into aflatoxins.

Aflatoxins↗

PubMed1975

Interaction of aflatoxin B1 with DNA.

The interaction of aflatoxin B1 with DNA was investigated. In the presence of native DNA the absorption spectrum of the toxin showed an obvious spectral shift in the region of 300-420 nm with an isosbestic point at 376 nm. DNA-bound aflatoxin is hydrolyzed in alkaline media more easily than the free toxin. The hydrolized form has a labile structure and can decompose further. The bound toxins are easily dissociated by heat as well as by salt, and all toxin molecules are released from DNA which remains double-stranded. Aflatoxin can bind to thermally denatured DNA as well, with an accompanying spectral shift which depends on the particular preparation of denatured DNA, and there was an isosbestic point at 380 nm. The complex of toxin and denatured DNA was stabilized by salt up to 0.1 M. Thus it was concluded that aflatoxin was bound with denatured DNA in a different form from native DNA. The number of binding sites of DNA was estimated by constructing Scatchard plots based on both spectral analysis and equilibrium dialysis. However, these show no definite value but fall in the region of 0.07 to 0.013, that is one toxin molecule per 80-140 nucleotide of native DNA. Several lines of evidence suggest the possibility that aflatoxin exists in aqueous solution as aggregates. The mechanism of the binding was discussed. It is noteworthy that the number of binding sites of DNA doubles by the presence of histones.

Aflatoxins↗

PubMed1989

Incidence of aflatoxin contamination in non-perishable food commodities.

To assess the incidence of aflatoxins contamination in different commodities, a representative countrywide study was conducted. One hundred composed samples of cereals, grains, spices, condiments and refined and raw sugars were analysed for aflatoxin B1, B2, G1 and G2. The moisture contents of all the food samples were also invariably determined. Only 6% of the samples namely maize and red chillies were found to be contaminated with aflatoxin B1 and B2 respectively. The percentage of samples contaminated among maize was 41.6 and the level of aflatoxin B1 ranged between 11.12 micrograms/Kg to 82.33 micrograms/Kg. In red chillies contamination was 25% and the level of aflatoxin B2 was 41.67 micrograms/Kg.

Aflatoxins↗