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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↗

PubMed1988

Serum albumin adducts in the molecular epidemiology of aflatoxin carcinogenesis: correlation with aflatoxin B1 intake and urinary excretion of aflatoxin M1.

Aflatoxin-serum albumin adducts in the blood of 42 residents of Guangxi Province, People's Republic of China, were determined and compared with intake of aflatoxin B1 (AFB1) and excretion of aflatoxin M1 (AFM1) in urine. Blood specimens were obtained during the same period that urine was collected and that diet was sampled. Serum albumin was isolated from blood by affinity chromatography on Reactive Blue 2-Sepharose and subjected to enzymatic proteolysis using Pronase. Immunoreactive products were purified by immunoaffinity chromatography and quantified by competitive radioimmunoassay. A highly significant correlation (r = 0.60, P less than 0.00003) of adduct level with AFM1 excretion was observed. An equally highly significant correlation of adduct level with intake (r = 0.69, P less than 0.000001) was also observed. From the slope of the regression line for adduct level as a function of intake, it was calculated that 1.4-2.3% of ingested AFB1 becomes covalently bound to serum albumin, a value very similar to that observed when rats are administered AFB1.

Aflatoxin B1↗

PubMed1978

Urinary excretion of aflatoxin M1 after administration of aflatoxin B1 in sucrose- or starch-rich diets.

1. Male Sprague--Dawley rats were given 630 g/kg sucrose or starch with 2 mg/kg aflatoxin b1 for periods of 75, 145 and 200 d, and the 24 h urinary excretion of aflatoxin M1 was measured. 2. Less aflatoxin M1 was excreted by the rats fed on the sucrose-rich diet compared to those fed on the starch-rich diet. This difference was especially marked when expressed per g metabolizing tissue. 3. It is concluded that sucrose probably decreases the activity of aflatoxin B1 metabolism in a similar way to its previously found effect on the drug-metabolizing enzyme.

Aflatoxins↗

PubMed1979

Production and characterization of antibody against aflatoxin M1.

Antibody against aflatoxin M1 was obtained after immunization of rabbits with bovine serum albumin-afla M1 oxime conjugate. The antibody has greatest binding efficiency for afla M1, and was less efficient for afla B1. Cross-reaction of antibody with aflatoxin Q1, aflatoxicol, and aflatoxin B2a was weak. Aflatoxin B2, G1, and G2 and afla B1-guanine adducts showed almost no cross-reaction with the antibody. The sensitivity of the binding assay for aflatoxin M1 detection is in the range of 1-10 ng per assay. Detailed methods for the preparation of the conjugate, production of immune serum, and methods for antibody determination are described.

Aflatoxins↗

PubMedDate not supplied

Thin layer chromatographic confirmation of aflatoxin M1 extracted from milk.

Aflatoxin M1 can be confirmed directly on a thin layer plate by reacting the toxin with a mixture of reagents containing p-anisaldehyde. This confirmatory procedure requires only 2 elutions in the same direction using 2 different solvents. The mixture containing p-anisaldehyde is overspotted on M1 after the plate has been developed in toluene-ethyl acetate-ethyl ether-formic acid (25 + 35 + 40 + 5). The plate is heated at 110 degrees C for 10 min and then developed in hexane-acetone-chloroform (15 + 50 + 35). The Rf value of the green fluorescent derivative is less than that of the M1 standard. This confirmatory procedure requires only one-dimensional TLC, so several sample extracts and the standard can be run simultaneously. The minimum detectable quantity of aflatoxin M1 on the TLC plate with this test is 0.3 ng. p-Anisaldehyde reagent solution may also be used as a spray reagent for the confirmation of aflatoxin M1. The procedures described were satisfactory for confirming the mycotoxin in spiked samples of powdered and liquid milk.

Aflatoxin M1↗

PubMed1977

[Thermal stability of aflatoxin M1 (author's transl)].

Aflatoxin M1 was added to Emmental hard cheese which was used for the production of processed cheese. The melting times at about 90 degrees C varied between 3 and 30 min. The analysis of the corresponding processed cheeses yielded a recovery of about 91% aflatoxin M1 on average. This means, that the aflatoxin M1 present in the hard cheese is essentially not destroyed during the production of processed cheese.

Aflatoxins↗

PubMed1984

Aflatoxin B1 metabolism in the rat: polyhalogenated biphenyl enhanced conversion to aflatoxin M1.

The effects of polychlorinated biphenyls (PCBs) and polybrominated biphenyls (PBBs) on the formation in vitro of aflatoxin Q1 and aflatoxin M1 from aflatoxin B1 by rat-liver microsomes were investigated. AFB1 metabolism by hepatic microsomes from PBB- and PCB-treated rats resulted in 16- and 30-fold increases, respectively, in levels of aflatoxin M1. The enhanced formation of aflatoxin M1 did not correlate with PBB and PCB stimulation of benzo[a]pyrene hydroxylase (AHH) activity. Studies in vivo clearly demonstrated enhanced secretion of aflatoxin M1 by female lactating rats with prior exposure to PCBs. PCB pretreatment enhanced the activity of mammary as well as hepatic tissue microsomal preparations in converting aflatoxin B1 to aflatoxin M1. Our findings indicate that PCB exposure increases the production of aflatoxin M1 in vitro and also increases the levels of aflatoxin M1 released into the milk.

Aflatoxin B1↗

PubMedDate not supplied

Behavior of 14C aflatoxin M1 during camembert cheese making.

Camembert cheeses are made from raw milk spiked with aflatoxin M1. Three aflatoxin M1 levels (7.5 micrograms/L, 3 micrograms/L, and 0.3 micrograms/L) are used. In curds 35.6, 47.1, and 57.7% of aflatoxin M1, respectively, are recovered, and in wheys 64.4, 52.9, and 42.3%, respectively, are recovered. During the first 15 days of storage, the aflatoxin M1 content of different cheeses decreases 25, 55, and 75%, respectively. A similar experiment is made with milk contaminated with 14C labeled aflatoxin M1. The same results are obtained, except for the behavior of aflatoxin M1 in cheese; the same 14C activity is recovered during storage for 30 days.

Aflatoxin M1↗

PubMed1987

Carcinogenicity of dietary aflatoxin M1 in male Fischer rats compared to aflatoxin B1.

Aflatoxin M1 (AFM), an hydroxy metabolite of the potent carcinogenic mycotoxin aflatoxin B1 (AFB) is frequently found in milk and other dairy products. Sufficient amounts of AFM were produced to study the carcinogenicity of this compound. AFM was fed to male Fischer rats starting at 7 weeks up to 21 months of age. Agar-based semisynthetic diets contained 0.0, 0.5, 5.0, and 50.0 micrograms/kg of AFM or 50 micrograms/kg of AFB. Hepatocellular carcinomas were detected in two of 37 rats and neoplastic nodules were found in six of 37 rats fed 50 micrograms/kg AFM between 19 and 21 months. No nodules or carcinomas were observed in the lower AFM dose groups. Nineteen of 20 rats fed a diet containing 50 micrograms/kg of AFB developed hepatocellular carcinomas by 19 months of age. Carcinogenic potency of the aflatoxins was reflected by morphometric quantitation of foci detected in hematoxylin and eosin stained sections. Three rats fed the diet containing 50 micrograms/kg AFM developed intestinal carcinomas. None were observed in other groups. Under the conditions of this experiment AFM was found to be a weak hepatic carcinogen compared to AFB and to possess intestinal carcinogenicity.

Aflatoxin B1↗

PubMed1979

[Appearance of aflatoxin M1 during the manufacture of Camembert cheese].

Several classic cheese making of camembert are made from raw milk spiked with Aflatoxin M1. Three Aflatoxin levels 7.5 microgram/l, 3 microgram/l are used. In respective curds 35.6, 47.1 and 57.7% of Aflatoxin M1 are recovered and 64.4, 52.9 and 42.3% in respective whey. During the first 15 days of storage the Aflatoxin M1 content of different cheeses decrease respectively 25, 55, 75%. A similar experience is made with a milk contamined in Aflatoxin M1 C14 labelled. Same results are recovered, except about behaviour of Aflatoxin M1 in cheese: a same C14 activity is recovered during storage for 30 days.

Aflatoxin M1↗

PubMed1984

Effects of chronic exposure to aflatoxin B1 and aflatoxin M1 on the in vivo covalent binding of aflatoxin B1 to hepatic macromolecules.

Induction of resistance to aflatoxin B1 (AFB1) binding to cellular macromolecules in the rat by chronic exposure to AFB1 and aflatoxin M1 (AFM1) was investigated. The binding of [14C]AFB1 to liver macromolecules was measured in F-344 rats fed 0.5 ppb or 50 ppb AFM1 or 50 ppb AFB1 for 41 wk. The animals then received an intragastric dose of [14C]AFB1 at 5 micrograms/kg and were sacrificed 6 h later. Hepatic DNA, RNA, and protein were isolated by chloroform-phenol extraction and hydroxylapatite chromatography. In animals preexposed to 50 ppb AFB1, labeled AFB1 binding to DNA, RNA, and protein was decreased by 72%, 74%, and 61%, respectively. Preexposure to AFM1 resulted in a small reduction in binding to nucleic acids. Glutathione transferase activity was increased by 133% in animals fed 50 ppb AFB1, by 48% in those preexposed to 50 ppb AFM1, and remained at control values in rats fed 0.5 ppb AFM1. These results suggest that the induction of detoxification enzymes following chronic exposure to aflatoxin might contribute to the reduction in covalent binding of AFB1 to macromolecules.

Aflatoxin B1↗

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↗

PubMed1996

Characterization of monoclonal antibodies to aflatoxin M1 and molecular modeling studies of related aflatoxins.

Aflatoxin M1 (AFM1) and seven structural analogs were used to investigate the correlation between antibody binding and the conformational and electronic properties of these molecules. Mice were immunized with AFM1-BSA and hybridomas secreting anti-AFM1 antibodies were isolated and characterized. The cross-reactivities of seven structurally similar aflatoxins were determined by competition enzyme-linked immunosorbent assay (cELISA). In an effort to correlate antibody binding with three-dimensional properties of the analogs, all of the aflatoxins (and the immunogen) were modeled and global energy minima were determined using molecular, mechanical and quantum mechanical methods. The results demonstrate that, for these molecules, loss of optimum structure and introduction of steric hindrance in the portion of the molecule that would fit into the antibody binding site are more important to binding than simply loss of a determinant group. Molecular computational techniques can give reasons for the wide variation in IC50 values observed between structural analogs and can be used as a tool for determining which conformational and electronic properties of molecules are most important for antibody binding.

Aflatoxin M1↗

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↗

PubMedDate not supplied

Use of immunoaffinity chromatography as a purification step for the determination of aflatoxin M1 in cheeses.

A method using immunoaffinity as a purification step for the determination of aflatoxin M1 in cheese is described. A simple solvent extraction with dichloromethane followed by a washing step with N-hexane gives a prepurified extract. A comparison between two ways of aflatoxin M1 purification, by solid-phase extraction clean-up and by immunoaffinity, was carried out. The use of immunoaffinity columns containing monoclonal antibodies against aflatoxin M1 gives the best result, i.e. a very clean preparation containing purified aflatoxin M1. The quantification of aflatoxin M1 is then performed by high performance liquid chromatography using fluorometric detection. This method was successfully carried out on naturally-contaminated and spiked cheeses. Recoveries are about 75%. The limit of quantification is 0.020 microgram of aflatoxin M1 per kg of cheese. This method seems suitable for use in monitoring programmes for aflatoxin M1 contamination in dairy products such as cheese.

Aflatoxin M1↗

PubMed1980

Rapid method for analysis of aflatoxin M1 in dairy products.

Four methods for determining aflatoxin M1 levels in fluid milk were compared in a search for a simple, routine analytical procedure.. Each method was tested with samples spiked at levels of 0, 0.1, 0.5, and 1.0 ppb. The 3 quantitative methods were comparable in sensitivity (0.1 ng/mL) and recoveries (80-90%). A new method, using a commercially available extraction column that contains an inert hydrophilic matrix to permit extraction of dairy products, is described. The milk is adsorbed on the column and aflatoxin M1 is eluted with chloroform-acetone (9 + 1). The extract is further purified on a small silica gel column and aflatoxin M1 is determined by TLC. This method was simpler and shorter, and was equally sensitive and reproducible in determining aflatoxin M1 in spiked and naturally contaminated fluid milk samples and in spiked nonfat powdered, condensed, and evaporated milk.

Chromatography, Thin Layer↗

PubMedDate not supplied

Robotic analysis of aflatoxin M1 in milk.

An automated aflatoxin M1 assay system capable of performing multiple unattended extractions and chromatographic analyses has been developed. A six-axis anthropomorphic laboratory robot and a flexible computer system are combined to operate a sample turntable, a multisolvent dispensing facility, a solid-phase extraction station, a vacuum manifold, an automatic HPLC sample preconcentration unit, an HPLC, a fluorescence detector and a computing integrator. The system is capable of handling bulk milk samples and can determine aflatoxins at the sub-micrograms/kg level with an accuracy and precision comparable to those of the manual methods of analysis. Time of analysis is reduced. The system can be run in an unattended mode of operation.

Aflatoxin M1↗

PubMedDate not supplied

Reverse phase liquid chromatographic determination and confirmation of aflatoxin M1 in cheese.

A systematic method is proposed for determination and confirmation of aflatoxin M1 in cheese by liquid chromatography (LC). A sample of cheese is extracted with chloroform, cleaned up on 2 silica gel columns followed by a Sep-Pak C18 cartridge, and chromatographed on a 5 microns octadecyl silica column with fluorometric detection. The sample extract or standard is treated with n-hexane-trifluoroacetic acid (TFA) (4 + 1) for 30 min at 40 degrees C. Analysis by LC with TFA-treatment of the extract provides quantitative data. Multiple assays of 5 samples of Gouda cheese spiked with aflatoxin M1 at levels of 0.5, 0.1, and 0.05 ng/g showed average recoveries of 93.2, 91.6, and 92.4%, with coefficients of variation of 2.63, 3.97, and 4.52%, respectively. Assay of 5 naturally contaminated cheeses resulted in 0.051-0.448 ng/g of aflatoxin M1. Limit of quantitation is about 0.01 ng/g. The identity of aflatoxin M1 is confirmed by treating aflatoxin M1 or the M2a derivative with TFA-methanol (or ethanol) (3 + 1). The TFA-methanol reaction products of M2a could be detected quantitatively.

Aflatoxin M1↗