Some cytotoxic effects of mixtures of simplexin and huratoxin obtained from the desert rice flower, Pimelea simplex.

Serial dilutions of mixtures of the closely related diterpenoid orthoesters simplexin and huratoxin were added to cultures of chicken embryo fibroblast cells and bovine erythroid cells; the mixture was lethal at concentrations of 100 micrograms/ml and 1 microgram/ml, respectively. Morphological changes were observed in the chicken embryo fibroblast cells exposed to concentrations of greater than or equal to 100 ng/ml; 1 microgram/ml caused a loss of definition of the mitochondrial cristae within 2 hr and vacuolation, crenation and shrinkage of the cells within 5 hr. These results support a hypothesis that the lesions and clinical signs shown by cattle affected with chronic Pimelea poisoning are caused by direct cytotoxic effects on the cells of the cardiovascular, haemopoietic, digestive and hepatic systems.