MASS-SPECTROMETRY OF POLYMETHOXYLATED FLAVONES

Mass spectra analyses of various polymethoxylated flavones (PMF) were obtained by gas chromatography-mass spectrometry (GC-MS). Among the compounds analyzed, mass spectra for 23 of them were recorded for the first time. In addition to common behavior of flavones under electron impact, such as retro-Diels-Alder reaction which gives a characteristic fragment (B-+degrees from the phenyl group of the flavone skeleton, new fragmentation pathways were identified and proposed. Thus, (B - 1)(+), which had never been mentioned, was a characteristic ion in the spectra of the 2'-methoxyflavones; this ion resulted from the loss of a hydrogen atom from the B-+degrees fragment. The (M - 19)(+) species was specific for the 3-methoxy PMF. The (M - 15)(+) fragment, already known in 6- and (or) 8-methoxy PMF, has been also characterized in 4'-methoxy PMF having no substituent in C-5 position.