近年,農産物に着生したFusarium菌の産生するカビ毒汚染が世界各国で注目されるようになった.我が国では麦類のdeoxynivalenol及びnivalenolについて,また諸外国では麦,コーンなどのdeoxynivalenolをはじめとするFusariumトキシンの自然汚染例に関する報告が多く見られるようになり,それらの汚染実態が解明されつつある.最近,カナダでは,小麦中のdeoxynivalenol汚染について2ppmのガイドラインを設けた.また,FDAでは,暫定的な値として小麦を原料とした最終製品で1ppm,製粉を行う小麦で2ppm,飼料で4ppm以下と勧告している.これらの諸外国の情勢から我が国においても早急に汚染調査のモニタリングを行い,汚染実態を把握するとともに,何らかの規制値を提示する時期にきているものと思われる.そこで著者は,市販食品及び農産物の汚染実態調査を行った.穀類等の農産物の多くは,加工食品の原料として,加工製造の工程を経て最終段階の製品として市販され,利用に際して水洗,加熱などの調理加工の行われる場合が多いが,調理加工後もトキシンが残存するか否かは人体への摂取との関連で重要な問題であり,関心事でもあることから調理,加工時の各種条件下におけるトキシンの消長を調査した. 一方,マイコトキシン汚染調査を行うとき,常に考慮しなければならないことの一つとして,サンプリングの問題がある.これらについては,aflatoxinの粒汚染についての報告例があるが,Fusariumトキシンについての報告例は見当らない.一般に,カビ毒の汚染は一粒単位の部分汚染であるため,化学分析の結果から母集団のトキシン量を推定するには,一粒あたりの汚染量と汚染粒の混在率により大きく影響を受けるためサンプリングの方法が重要な問題となる.そこでサンプリング方法を検討する際,汚染の実態を解明したうえで,試料採取及び秤取量などを決めることが今後重要な課題になるものと考えるので,それらについても言及する.

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The survey of 22 commercial samples of imported green coffee beans for aflatoxins and ochratoxin has been conducted in 1982-1983. Ochratoxin A was detected in 4 samples at a level of 9.9-46μg/kg but all samples analyzed were negative for aflatoxins. Major contaminants of the samples were Aspergillus glaucus group, A, niger group, A. flavus group, A. ochraceus group and members of the Mucorales. Among the contaminants, the ability of A, flavus and A, ochraceus isolates to produce the mycotoxins was examined. Particularly, 9 isolates of A. ochraceus group produced high levels of ochratoxin A on artificial polished rice and ground coffee media (yields of ochratoxin A: 48.3-750μg/g on rice and 8.06-130μg/g on coffee, respectively). Addition of caffeine (0.1-1.0%) on MY-20 agar medium in a Petri dish resulted the delayed growth of A. ochraceus strain S-235-100, a representative isolate from the green coffee beans, but had little effect on its ochratoxin production. On the basis of the results obtained in this study, it is apparent that green coffee beans might be susceptible to A, ochraceus infection and subsequent ochratoxin production.

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The effects of dechlorinated dyclochlorotine (deCl-CC) on murine liver cells were compared with those of Cyclochlorotine (CC). The deCl-CC were prepared by treating CC with 25% ammonia water-methanol (1:5). Compared with the morphological changes induced by CC in hepatocytes such as vacuole-formation, a marked reduction in cytotoxicity was observed in the rat as well as mouse hepatocytes treated with deCl-CC in in vivo and in vitro systems.

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The anthrapuinone mycotoxyins, emodin and skyrin from Penicillium islandicum Sopp, were investigated for their interactions with bovine serum albumin (BSA) using a technique of spectrophotometry in search for their differences in physical properties by which the differences in their in vitro biological activities could be interpreted. BSA produced characteristic spectral alterations of emodin and skyrin in the visible light region, accompanying marked red shift of their absorption maxima. Spectrophotometric titrations of emodin and skyrin with increasing concentrations of BSA gave molar ratios of 2.5 and 5, respectivery, for their binding to BSA. The absorption spectra of emodin and skyrin were affected by pH changes of the system. The pK were significantly shifted to lower pHs in the presence of BSA. The amplitude in the BSA-induced pK shift of skyrin was significantly larger than that of emodin. Sodium dodecylsulfate (SDS) abolished the BSA-induced spectral alterations of emodin and skyrin.

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Violaceol-I, -II, and violaceic acid from a toxigenic fungus Ernericella violacea were examined for their uncoupling effect on oxidative phosphorylation of isolated rat liver mitochondria. It was found that toxic metabolites violaceol-I and -II were uncouplers to mitochondrial respiration and non-toxic metabolite violaceic acid was not. Violaceol-I and -II induced large amplitude swelling of mitochondria in isotonic alkali salt solutions and violaceic acid again did not. The uncoupling activities of violaceols were found to be gradually diminished and were finally completely lost when violaceols solution was kept at room temperature due to their chemical instabilities. However instead of uncoupling effect, an inhibitory effect on state 3 respiration was increased, causing a prominent decrease in RC index of mitochondrial respiration.

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A simple and sensitive method for chemical analyses of three trichothecene mycotoxins (deoxynivalenol, nivalenol and fusarenon-X) has been developed. Extraction of the toxins from sample with 200 ml of aqueous acetonitrile (acetonitrile: water=150:50) was followed by clean-up using a Florisil column and a Sep-pak silica cartridge, and then determination of the toxins were carried out with GC (ECD) and GC-MS (mass fragmentography). The detection limits of deoxynivalenol, nivalenol and fusarenon-X were 2, 2 and 4 ppb respectively, when the method was applied to rice, wheat, corn and soybean.

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