6α, 7β, 9α-Trihydroxy-8(14), 15-isopimaradine-20, 6-γ-lactone(PT)produced by Phoinopsis sp., one of the pathogenic fungi of pine wilt disease, was transformed to 7-oxo-6 α, 9 α-dihydroxy-8(14), 15-isopimaradiene-20, 6-γ-lactone (OPT) and others by pine callus. The transformation was inhibited by α-naphthoflavone added in the metabolic system. OPT was considered active form of PT, because OPT had a α, β-unsaturated ketone in the structure. OPT was obtained from PT by chemical oxidation, too.
A direct enzyme-linked immunosorbent assay (ELISA) for the quantitation of aflatoxin B1 (AFB1) was developed by the utilization of horseradish peroxidase (HRP) labelled anti-AFB1 monoclonal antibody and 96-well immunomicroplate coated with AFB1-bovine serum albumin conjugate. The detection limit for AFB1 was ca. 5 pg/assay. A quick ELISA system was also developed using the 8-well immunomicroplate, and ca. 50 pg to 5 ng/assay of AFB1 were quantitated within 10 min.
O-Methylsterigmatocystin (OMST)-producing strain (No. 35-8) of Aspergillus parasiticus was isolated from imported peanuts in 1983. The strain No. 35-8 was taxonomically identified with A. flavus subsp. parasiticus sensu Kurtzman et al. (1986), but produced no detectable aflatoxins on peanut meal medium. The OMST accumulation in solid culture of this strain on peanut meal was thus confirmed by comparison of chromatographic behavior on TLC and HPLC, and also by UV spectra and mass spectra data with those of OMST standard. Furthermore, bioproduction of OMST on three kinds of substrates by this strain was measured and the following yields were obtained: 700μg/g on peanut meal, 350μg/g on polished rice and 180μg/g on YES agar medium, respectively.
Several polyhydroxyanthraquinone mycotoxins such as emodin, skyrin from Penicillium islandicurn and averufin, versicolorin A from Aspergillus versicolor inhibit ATP biosynthesis in mitochondria by uncoupling oxidative phosphorylation. These anthraquinones are characterized by a hydroxyl group at β-position of the anthraquinone nucleus. In the present study, the uncoupling activity of polyoxyanthraquinones which have no hydroxyl group at the β-position was examined by means of islandicin and iridoskyrin from Penicillium islandicum and several dihydroxyanthraquinones. It was confirmed that the presence of the hydroxl group at the β-position rather than the γ-position was very important for the potent uncoupling effect on oxidative phosphorylation in mitochondria.
Chicken meat, wheat and porcine plasma spiked with various amounts of ochratoxin A were extracted with 0.5% metaphosphoric acid-chloroform (1 : 1), acetonitrile-water (3 : 1) and chloroform alone, respectively, and the resulting extracts were analyzed by an enzyme-linked immunosorbent assay (ELISA) based on monoclonal antibody specific to ochratoxin A. The detection limit of ochratoxin A in these samples was 1 ng/g in the present simplified ELISA.
Certain Egyptian polished rice examined on several toxic substances was found to be naturally contaminated with aflatoxins (AF). This rice was sent to Japan by a Japanese resident in Cairo, who suspected the rice bought there was a cause of his illness. The rice was mingled with pale yellow grain, and apparently not suitable to eat according to the inspection guideline for agricultural products in Japan. As residual pesticides, phenitrothion and BHC were found from the rice, although their concentrations were lower than their standard requirements. We determined aflatoxins, deoxy-nivalenol and nivalenol on the rice and found AF B1 (8 ppb), AF B2 (2 ppb), which were confirmed by GC/MS. Twelve strains of A. flavus were isolated from the rice, and 1 strain produced AF B1 and B2 at the concentrations of 43 ppm and 3 ppm respectively.