ISOLATION AND CHARACTERIZATION OF ENNIATINS FROM FUSARIUM-AVENACEUM DAOM-196490

Dried mycelia from a 15 L stirred-jar fermentation culture of Fusarium avenaceum (DAOM 196490) were extracted with dichloromethane and partitioned between hexane and methanol/water. Recrystallization of the hexane fraction yielded 6.750 g of a crude mixture of enniatins. Fast atom bombardment mass spectrometry showed, in accord with previous studies, that enniatin A was the predominant enniatin present, with smaller amounts of enniatins A1 and B1. HPLC purification of 500 mg of the enniatin mixture resulted in the isolation of 300 mg of enniatin A, 114 mg of enniatin A1, 9 mg of enniatin B1, and 46 mg of a new, N-methylleucine-containing enniatin (A2). This is the first reported isolation of a pure N-methylleucine-containing enniatin from Fusarium, though the existence of such compounds had previously been inferred from hydrolysis and NMR data. The purification and complete characterization of enniatins A1, B1 , and A2 are reported.