Aflatoxin BI and

Palmitic and stearic acids aflatoxins Bi and Bi 15 to 35% unseparated fatty acids intensified the fluorescence when investigating com extracts [224]... 

The normal pathway toward excretion of foreign molecules like aflatoxin Bi and dibenzo [a,/]pyrene, however, also involves nucleophilic substitution reactions of their epoxides. 

Trichloroethylene Vinyl chloride CYP3A4 Acetaminophen Aflatoxin Bi and Gi 6-Aminochrysene Benzo[a]pyrene 7,8-dihydrodiol Cyclophosphamide Ifosphamide 1-Nitropyrene Sterigmatocystin Senecionine... 

It turned out that aflatoxin was actually a mixture of four different but closely related chemicals. All possessed the same molecular backbone of carbon, hydrogen, and oxygen atoms (which backbone was quite complex and not known to be present in any other natural or synthetic chemicals), but differed from one another in some minor details. Two of the aflatoxins emitted a blue fluorescence when they were irradiated with ultraviolet light, and so were named aflatoxin Bi and B2 the names aflatoxin Gi and G2 were assigned to the green-fluorescing compounds. The intense fluorescent properties of the aflatoxins would later prove an invaluable aid to chemists interested in measuring the amount of these substances present in various foods, because the intensity of the fluorescence was related to the amount of chemical present. 

Both benign and malignant liver tumors may arise from exposure to hepatotoxins and can be derived from various cell types. Thus, adenomas have been associated with the use of contraceptive steroids and exposure to aflatoxin Bi, and dimethylnitrosamine can produce hepatocellular carcinomas, whereas vinyl chloride causes hemangiosarcomas derived from the vasculature (see chap. 7). 

Work Item H determination of aflatoxin Bi and total aflatoxins by immunoaffinity column clean-up and HPLC in fig paste, pistachios, peanut butter and paprika powder. 

Bhatnagar D, Cleveland TE, Kingston DGI Enzymological evidence for separate pathways for aflatoxin Bi and B2 biosynthesis. Biochemistry 1991 30 4343-4350. 

A number of chemicals with demonstrable suppression of immune function produce this action via indirect effects. By and large, the approach that has been most frequently used to support an indirect mechanism of action is to show immune suppression after in vivo exposure but no immune suppression after in vitro exposure to relevant concentrations. One of the most often cited mechanisms for an indirect action is centered around the limited metabolic capabilities of immunocompetent cells and tissues. A number of chemicals have caused immune suppression when administered to animals but were essentially devoid of any potency when added directly to suspensions of lymphocytes and macrophages. Many of these chemicals are capable of being metabolized to reactive metabolites, including dime-thylnitrosamine, aflatoxin Bi, and carbon tetrachloride. Interestingly, a similar profile of activity (i.e., suppression after in vivo exposure but no activity after in vitro exposure) has been demonstrated with the potent immunosuppressive drug cyclophosphamide. With the exception of the PAHs, few chemicals have been demonstrated to be metabolized when added directly to immunocompetent cells in culture. A primary role for a reactive intermediate in the immune suppression by dimethylnitrosamine, aflatoxin Bi, carbon tetrachloride, and cyclophosphamide has been confirmed in studies in which these xenobiotics were incubated with suspensions of immunocompetent cells in the presence of metabolic activation systems (MASs). Examples of MASs include primary hepatocytes, liver microsomes, and liver homogenates. In most cases, confirmation of a primary role for a reactive metabolite has been provided by in vivo studies in which the metabolic capability was either enhanced or suppressed by the administration of an enzyme inducer or a metabolic inhibitor, respectively. 

At this pH, the phosphotriesters formed mainly lose alcohol to re-form the phosphodiester, but at higher pH, hydrolysis with chain scission takes place. Alkylation also proceeds at nucleophilic centres on the base and sugar moieties, and the modification likely to cause most damage in vivo has not been defined. Studies involving aflatoxin Bi and benzanthracene derivatives have tended to concentrate on the modification of the bases, to the exclusion of possible effects at the phosphate group, but there is good evidence that the latter should not be ignored. ... 

Busbee DL, Norman JO, Ziprin RL. 1990. Comparative uptake, vascular transport and cellular internalization of aflatoxin BI and benzo(a)pyrene. Arch Toxicol 64(4) 285-290. 

The usefulness of immunochemical techniques for the fluorimetric determination of mycotoxins has been widely demonstrated. In addition to the use of immunoaffinity column cleanup followed by LC with fluorescent detection, several FIAs have been described for the determination of aflatoxins, deoxynivalenol, and fumonisins using fluorescence polarization immunoassay or time-resolved fluor-oimmunoassay. Also, although the application of flu-oroimmunosensors to food analysis has been relatively limited, there are some examples of the use of this approach to the determination of some mycotoxins such as aflatoxin Bi and fumonisin B2. 

The problem with the simple TLC analysis of aflatoxins is that many natural products fluoresce blue or green under UV and many of these compounds have an Rp value close to, or even identical with, that of one of the four common aflatoxins (Figure 1). The early literature contains a number of false-positive reports of the presence of aflatoxins, and even their production by species of mold other than Aspergillus flavus, A. parasiticus, and A. nomius, so it is essential that a confirmatory test be carried out such as derivatization coupled with two-dimensional TLC. In the case of the aflatoxins, a useful confirmatory test is to derivatize as the hemiacetals with trifluoroacetic acid by superimposing 2 pi of a 50% solution of the reagent in chloroform onto the spot of both the unknown and a standard marker before chromatography. Aflatoxins Bi and Gi, but not B2 and G2, form hemiacetals that have the same fluorescence as the parent compound but run significantly more slowly... 

Aflatoxins in cottonseed products - TLC and liquid chromatography methods 982.24 Aflatoxins Bi and Mi in liver - TLC method... 

Renal epithehal neoplasias, histologically similar to human kidney adenocarcinoma, were found in over one-half of rats ingesting 1.0 ppm aflatoxin Bi and about one-quarter of rats given 0.5 or 0.25 ppm for 147 days (Epstein et al. 1969). 

Metabolizing systems for in vitro short-term tests are most frequently derived from rat liver, but other species deserve consideration. Significant differences exist in the hepatic metabolism of various rodent species. For example, guinea pig liver does not activate A -2-fluorenylacetamide. Aflatoxin Bi and... 

Mycotoxins have been used extensively by Ueno and Kubota.These workers have found that 6 Penicillium toxins, 5 Aspergillus toxins, and 2 Fusa-rium toxins are positive in the rec-assays, including 8 mycotoxins that arc known carcinogens in animals citrinin, penicillic acid, patulin, (-)-luteoskyrin, (-l-)-rugulosin, aflatoxin Bi and Gi, and sterigmatocystin (Table 9). 

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