Recently, there was a major controversy when a substance called "flabelliferine," a research material for malaria treatment, was detected in a red yeast rice health food product from Kobayashi Pharmaceutical, a Japanese pharmaceutical and chemical company. While flabelliferine is a substance that has little to do with red yeast rice itself, its toxicity controversy is heating up.

Flabelliferine is a natural compound in the form of a yellow powder, a metabolic product of Penicillium viticola (FKI-4410), a type of green mold. While this substance was first reported in 1932, it started to attract attention as a potential new anti-malaria drug because it exhibited a strong insecticidal effect against chloroquine-resistant malaria parasites.

However, there was a fatal problem with flabelliferine itself. In mouse experiments, it showed strong toxicity, with 4 out of 5 mice dying within 3 days when administered subcutaneously at 5 mg/kg twice. As a result, the drug development of flabelliferine itself was discontinued, and the research direction was shifted to the study of derivatives with modified chemical structures, such as "tropon," "tropolone," "hinokitiol," and "7-hydroxytropolone."

So why was flabelliferine detected in Kobayashi Pharmaceutical's red yeast rice health food product? Experts believe that flabelliferine-producing mold contaminated the red yeast rice during the manufacturing process. Red yeast rice undergoes a two-stage fermentation process called "jongguk" and "je guk," requiring strict temperature and humidity control. It is estimated that external mold contamination occurred at one of these stages.

Meanwhile, there is controversy over whether flabelliferine itself induces kidney toxicity. Shinjiro Inoue, Professor Emeritus at Tokyo Institute of Technology, pointed out that "it is difficult to conclude that flabelliferine is highly toxic based solely on the contents of the research paper on its toxicity." The research paper in question involved an experiment where flabelliferine was administered to malaria-infected mice, and while 4 mice died, it is impossible to definitively determine if flabelliferine was the sole cause of death, he explained.

In addition, Professor Inoue argued that the toxicity of the interaction between flabelliferine and "monacolin," another ingredient in red yeast rice, should be considered. The fact that adverse cases have only been found in red yeast rice products with high monacolin content suggests that it is an oversimplification to consider this solely as a problem with flabelliferine.

As health food issues become more complex, the controversy surrounding flabelliferine is also intensifying. Further experiments are expected to clarify the toxicity of flabelliferine and the mechanism of kidney toxicity. Kobayashi Pharmaceutical must alleviate public concerns by swiftly identifying the cause and disclosing information.