Electron ionization mass spectrometry of curcumin analogues: an olefin metathesis reaction in the fragmentation of radical cations
作者:Ben L. M. van Baar、Jelle Rozendal、Henk van der Goot
DOI:10.1002/(sici)1096-9888(199804)33:4<319::aid-jms636>3.0.co;2-u
日期:1998.4
The natural compound curcumin, used in cosmetics, traditional medicines and as a spice in food, is known as a multi-factorial anti-inflammatory agent. To study the anti-inflammatory activity of curcumin derivatives, 24 analogues were synthesized and their structures were confirmed by H-1 MMR and electron ionization (EI) mass spectrometry. Most signals in the EI mass spectra can be attributed to commonly known fragmentations, but the formation of ring-substituted 1,2-diphenylethene (stilbene)-type radical cations, observed in the spectra of all compounds investigated and resulting in the base peak for some compounds, requires a peculiar rearrangement. Metastable ion spectra and C-13 labelling studies show that the stilbene-type ions are formed directly from the molecular ions and contain the two original aryl groups and the 1 and 7 carbon atoms of the olefinic system. It is proposed that the formation of stilbene-type ions results from an intramolecular olefin metathesis reaction; this suggestion is supported by semi-empirical (MNDO/PM3) calculations. (C) 1998 John Wiley & Sons, Ltd.