Lack of Mutagenicity of Some Phytoestrogens in the Salmonella/mammalian Microsome Assay

8 phytoestrogens were tested for mutagenicity using a variation of the Salmonella/mammalian microsome (or Ames) assay. Zearalenone is a mycotoxin produced by a grain contaminant, Fusarium graminearum (Gibberella zeae) and the isomers of zearalanol are reduced derivatives of this compound. The remaining compounds are all flavonoids which occur naturally at relatively high concentrations in many plants, particularly legumes. 4 of these flavonoids (daidzein, genistein, formononetin and biochanin-a) are isoflavones and the 5th, coumestrol, is a coumestan. Each compound was tested at several concentrations ranging from 1--500 micrograms per plate. The microsomal fracton was obtained from Aroclor 1254 (a PCB)-induced rat livers. None of the compounds tested was mutagenic to Salmonella strains TA1538, TA98 or TA100 at any concentration.