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Electron ionization mass spectrometry of curcumin analogues: an olefin metathesis reaction in the fragmentation of radical cations
Author(s) -
van Baar Ben L. M.,
Rozendal Jelle,
van der Goot Henk
Publication year - 1998
Publication title -
journal of mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 121
eISSN - 1096-9888
pISSN - 1076-5174
DOI - 10.1002/(sici)1096-9888(199804)33:4<319::aid-jms636>3.0.co;2-u
Subject(s) - chemistry , electron ionization , fragmentation (computing) , mass spectrum , mass spectrometry , intramolecular force , ion , olefin fiber , metathesis , ionization , mndo , photochemistry , medicinal chemistry , computational chemistry , organic chemistry , molecule , polymerization , chromatography , polymer , computer science , operating system
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 1 H NMR 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 13 C 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. © 1998 John Wiley & Sons, Ltd.