New analogues of aspergillic acid derived from methionine.

Aspergillus flavus PRL 932 grown on 2% yeast extract plus 1% methionine produced some compounds which, according to their structures, were probably derived in part or completely from methionine. These included 3-(methylthio)-propionic acid, trans-3-(methylthio)-acrylic acid, and various 1-hydroxy-2(1H)-pyrazinones (HPY) with 2-(methylthio)-ethyl (MTE) substituents. The latter compounds were identified by proton magnetic resonance and mass spectra as 3,6-di-MTE-HPY, 3-MTE-6-isopropyl-HPY, 3-isobutyl-6-MTE-HPY, 3-MTE-6-isobutyl-HPY, and 3-MTE-6-sec-butyl-HPY.Changes in media composition, including supplementation with either L-leucine, L-isoleucine, or L-valine changed the relative amounts of various HPYs produced. The results indicated that amino acids competed as precursors for the biosynthesis of HPYs and that L-leucine and L-isoleucine were utilized more effectively than was L-methionine.