Biosynthesis of diaporthin and orthosporin by Aspergillus ochraceus.

Diaporthin and orthosporin were characterised from the fungus Aspergillus ochraceus D2306. Diaporthin was identified by high-resolution electron impact mass spectrometry and 1H and 13C NMR spectroscopy, from which new spectroscopic assignments were made. Orthosporin was also identified by mass spectrometry and both fungal metabolites are reported for the first time as co-metabolites and also as products of A. ochraceus. The methylation inhibitor ethionine affected production of both diaporthin and orthosporin in spite of no obvious methylation step in the biosynthesis of orthosporin, implying that extracellular orthosporin may arise by de-O-methylation of diaporthin. The biosynthetic origin of diaporthin was demonstrated by incorporation of [1-14C]acetate and [methyl-14C]methionine administered in early idiophase.