Sterigmatocystin-a Masked Potent Carcinogenic Mycotoxin

Abstract

Sterigmatocystin (stg), a related compound of aflatoxin B₁ (af B₁) is a secondary metabolite of a wide variety of fungi species. Stg is a compound in which a substituted anthraquinone is fused to the bisdihydrofuran ring. An unsaturated 2, 3 bond in the bis-dihydrofuran ring is closely related to the biological activities of stg. Activated stg is covalently bound with DNA at the N⁷-⁻guanyl position in the target cells. Acute toxicity of stg is infact, rather weak. The lower toxicity in in vivo systems may be due to the poor absorption rate of stg from the digestive tracts. The data obtained from in vitro systems show that stg is as toxic as af El when the inycotoxin contacts directly with the cells. In spite of its low acute toxicity, stg shows a potent mutagenicity as well as carcinogenicity. As for its carcinogenicity, the target organ of stg in rats is the liver, and those in mice are the lung and blood capillaries. Stg induced malignant tumors not only in the target organs, but also at the site where the mycotoxin was applied. As a hepatocarcinogen stg is about 150 times less potent than af B₁. However, it is at least 10 times more potent than the other well-known hepatocarcinogens. Due to the wide occurrence of the fungi which produces stg, the large amounts of the thusly developed compound, and the potent carcinogenicity because of an un-noticeable outbreak of stg-intoxication, stg is one of the most dangerous foodstuff contaminants.