Structure of the host-specific toxins produced by the fungal pathogen Periconia circinata

Four metabolites named peritoxins A and B and periconins A and B have been isolated together with the known metabolite circinatin from culture filtrates of the fungal pathogen Periconia circinata. Peritoxins A and B, which correspond to the P. circinata toxins Ia and IIa partially characterized in previous work, are selectively toxic to genotypes of Sorghum bicolor susceptible to the pathogen, whereas periconins A and B are biologically inactive. Combination of instrumental analysis and chemical degradation has led to structural assignments for each of the four compounds; only the configuration at some of the chiral centers remains undefined. Structural comparison suggests a precursor role for circinatin in the formation of the peritoxins and the periconins.