Biosynthesis of diaporthin and orthosporin by Aspergillus ochraceus

Diaporthin and orthosporin were characterised from the fungus Aspergillus o chraceus D2306. Diaporthin was identified by high-resolution electron impac t mass spectrometry and H-1 and C-13 NMR spectroscopy, from which new spect roscopic assignments were made. Orthosporin was also identified by mass spe ctrometry 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 o f [1-C-14]acetate and [methyl-C-14]methionine administered in early idiopha se. (C) 2001 Elsevier Science Ltd. All rights reserved.