Isolation and structure elucidation of four fatty acid derivatives of the mycotoxin fusarochromanone produced by Fusarium equiseti

Abstract

Four compounds were found in rice cultures of Fusarium equiseti (Alaska 2-2). Analysis by mass spectrometry (EI, PCI, and FAB) indicated that compounds I, II, III, and IV had molecular formulas of C33H52N2O6 (572.3755), C35H52N2O6 (596.3764), C35H54N2O6 (598.3884), and C35H56N2O6 (600.4149), respectively. Hydrolysis of a mixture of the four compounds with 1.2 N HCl in 80% methanol yielded six compounds. They were identified by mass spectrometry as 2,2-dimethyl-5-amino-6-(3'-amino-4'-hydroxybutyryl)-4-chromone(fusarochromanone, TDP-1),2, 2-dimethyl-5-amino-6-(3'-N-acetyl-4'-hydroxybutyryl)-4- chromone(3'-N-acetylfusarochromanone, TDP-2), and methyl esters of four fatty acids, including 14-methylpentadecanoic acid, 10,12-octadecadienoic acid, 9-octadecenoic acid, and 16-methylheptadecanoic acid. The fatty acid methyl esters were resolved by gas chromatography with a capillary column. The locations of double bonds in the fatty acyl moieties of compounds II and III were determined by the EI mass spectra of their TMSO derivatives. The structures of the four compounds were determined to be 3'-N-acetyl-4'-O-fatty acylated fusarochromanone. The mass spectral analysis was supported by 1H NMR and infrared spectral data.