Fusarin C: isolation and identification of two microsomal metabolites

Fusarin C (FC), a metabolite formed by Fusarium moniliforme, is, with microsomal activation, genotoxic. Two metabolites of FC, fusarin Z (FZ) and fusarin X (FX), have been isolated from an in vitro metabolic activation system using microsomal mixtures from phenobarbital-induced rat livers and their chemical structures identified. FZ and FX are 500 and 60 times more mutagenic than FC in the Ames test, respectively. Both result from hydroxylation at the 1-position of FC. FZ is a gamma-lactone involving isomerization of the 2,3-double bond and intramolecular transesterification between the 21-methyl ester and the newly formed 1-hydroxyl group. FX, however, could not be converted to FZ by the microsomal system.