Comparative toxicity of scirpentriol and its acetylated derivatives

Scirpentriol (STO) and its seven acetylated derivatives, 3-, 4- and 15-monoacetoxyscirpenol (MAS), 3,4-, 3,15-, and 4,15-diacetoxyscirpenol (DAS), and 3,4,15-triacetoxyscirpenol (TAS) were compared for their acute oral lethality in broiler chicks, lethality in brine shrimp, and dermal toxicity in guinea pigs. Of the eight toxins, 4,15-DAS was the most toxic in the three assays, 3-MAS was the least toxic in brine shrimp and dermal assays, and 3,4-DAS was the least toxic in the chick assay. There was a difference of about a 100-fold and 20-fold, respectively, between 4,15-DAS and 3-MAS in dermal toxicity and brine-shrimp toxicity, as well as a difference of more than 16-fold between 4,15-DAS and 3,4-DAS in chick toxicity. In general, a free hydroxy group at the 3-position was a primary determinant of toxicity. Toxicity in the scirpenol family did not follow precisely the pattern reported earlier for the T-2 toxin family of trichothecene toxins, in which a decrease in the number of acyl groups was accompanied by a decrease in toxicity. At necropsy, the predominant sign in chicks was petechial hemorrhaging, primarily in the gastrointestinal tract and in the vascular beds of the beaks and the toe nails. The 4,15-DAS and 15-MAS were about 3 times more toxic in chicks than aflatoxin. All members of the scirpenol family of trichothecene mycotoxins appeared sufficiently toxic to warrant attention whenever field outbreaks occur. Apparently, brine shrimp and dermal assays are successful predictors of chick lethality by the more toxic trichothecenes and are less suitable for predicting the activity of the less toxic trichothecenes.