[Safety of rice grains and mycotoxins - a historical review of yellow rice mycotoxicoses].

Aflatoxins, the most powerful mycotoxins, were brought to the attention fo the people in the early 1960s with the outbreak of the turkey "X" disease in England. However, the history of mycotoxin research in Japan began 100 years ago. In 1891, Sakaki demonstrated that moldy, unpolished rice was fatal to experimental animals, with symptoms indicating paralysis of the central nervous system (Shoshin-kakke). In 1920, Prof. I. Miyake and Dr. Takada first reported that Penicillium commune, which was known as a causal agent of "Mossy diseased rice" was found to be toxic to experimental animals by feeding the moldy rice to rabbits and rats.With such a historical background, taking the idea of "rice, fungus and toxin" as a working hypothesis, Miyake and his co-workers discovered the first sample of yellow rice grains from Taiwanese and domestic rice, from which was isolated a species of Penicillium and later identified it with P. citreonigrum (=P. toxicarium). The fungus produced a highly toxic metabolite, citreoviridin. Unfortunately because this study was published during wartime, it failed to alert the world to the potential or actual dangers of the toxicity of common molds. After World War II, Japanese people suffered for some years from a shortage in domestic rice production and depended on foreign countries to supply rice, which led to the toxicological screening on fungal isolates from polluted rice grains by Dr. Tsunoda and his co-workers. AMong the isolates from imported rice, there were two species of Penicillium which were particularly associated with high toxicity; P. islandicum responsible for brownish discolored rice, and P. citrinum responsible for yellowish rice. P. islandicum produces two hepatotoxic metabolites: luteoskyrin and cyclochlorotine, while a nephrotoxic of P. citrinum is citrinin. These toxicological characters, including the induction of cancer and chemical structures, were studied by Profs. uraguchi, Saito, Shibata, Tatsuno and their co-workers. In this way, toxic disturbances associated with the consumption of rice contaminated with these Peniciliium species occurred and became known under the collective name of the "Yellow rice syndrome". Although no human cases of poisoning were recorded, scientists in the field of mycotoxin research recommended to the Japanese Government that administrative action should be taken to protect the people against any possible hazards from "yellow rice". Consequently, mycological inspections of imported rice were started by the government. The safety control system for domestic rice during post-harvest handling and long-term storage has been progressively established after learning of these problems.